Basic RAID concerns and Linux OS

Basic RAID concerns and Linux OS

Post by n.. » Wed, 29 Mar 2006 02:54:00



In our small business, we have to hold onto gigs of data. And sadly,
disgustingly, we don't have any good backup (periodic DVD burning when
we can) and the PC holding the info just has a couple of ATA HD's.

We're needing to put together a file server, and I'm looking into mobos
that handle RAID 10. From what I can see, that's the best balance of
efficiency and performance even with the 50% size usage.

Here're my questions:
I am finding it hard to find info on how the RAID is managed and if a
drive fails, how to replace it and rebuild the array. Some info I
REALLY need to know before I set one up. =)
I've found lots of info about what an array does but no real meat on
managing an array.
Any pointers of where I can go to find actual how-to's would be
appreciated.

I'm pretty comfortable with Fedora Core. But, I'm also looking into
Slackware since a lot I've found indicates it's a bit (or a lot) more
stable, secure, and tested.
So, does the OS handle array management, or software apart from the OS?
(When I installed a SATA on my own PC I had to install some HD software
that loads up before the OS does.
So does picking the OS matter too much when considering RAID?

And, how hard is it to replace a RAIDed drive?
If I have a RAID 10 and a drive goes bad, is it as easy as replacing
the drive and selecting something in a program that "rebuilds the
array"?
(How would I know a drive's gone bad anyway? Does the RAID do a
constant parity check and whatnot and let me know of abnormalities? Or
do I have to run an FSCK or something now and then?

Thanks for any feedback and information!
-Liam

 
 
 

Basic RAID concerns and Linux OS

Post by Michael Heimin » Wed, 29 Mar 2006 03:08:36



Quote:> In our small business, we have to hold onto gigs of data. And sadly,
> disgustingly, we don't have any good backup (periodic DVD burning when
> we can) and the PC holding the info just has a couple of ATA HD's.

USB2 cases and large IDE hds are cheap enough for backup
purposes.

[..]

Quote:> Here're my questions:
> I am finding it hard to find info on how the RAID is managed and if a
> drive fails, how to replace it and rebuild the array. Some info I
> REALLY need to know before I set one up. =)

All this is explained (software raid howto - www.tldp.org)

[..]

--
Michael Heiming (X-PGP-Sig > GPG-Key ID: EDD27B94)

#bofh excuse 209: Only people with names beginning with 'A'
are getting mail this week (a la Microsoft)

 
 
 

Basic RAID concerns and Linux OS

Post by Gran » Wed, 29 Mar 2006 05:35:41



Quote:>We're needing to put together a file server, and I'm looking into mobos
>that handle RAID 10. From what I can see, that's the best balance of
>efficiency and performance even with the 50% size usage.

Only fools use mobo dual drive RAID as a data backup arrangement,
and you join their ranks the day the box cannot boot and you panic.

Quote:>I'm pretty comfortable with Fedora Core. But, I'm also looking into

FC is redhat's beta testing distro, unstable.

Decide if you need high data availability --> proper RAID5, or a
decent data backup strategy.  Dual drive RAID is not very useful,
except to the supplier who sells an extra drive.

Unless a RAID solution is done properly, you often find the entire
RAID degraded as a failure event may take out > 1 drive.  This is
independent of which GNU/Linux distro you use.  I use slackware,
because it is stable, and no stupid binaries shielding the config
files.  

One needs to backup OS configuration (one tar command) and manage
user data backups -- 'it depends'.  No point in backing up the OS,
that can be reinstalled.

Grant.
--
Memory fault -- brain fried

 
 
 

Basic RAID concerns and Linux OS

Post by Joseph2 » Mon, 03 Apr 2006 10:30:15



> In our small business, we have to hold onto gigs of data. And sadly,
> disgustingly, we don't have any good backup (periodic DVD burning when
> we can) and the PC holding the info just has a couple of ATA HD's.

> We're needing to put together a file server, and I'm looking into mobos
> that handle RAID 10. From what I can see, that's the best balance of
> efficiency and performance even with the 50% size usage.

> Here're my questions:
> I am finding it hard to find info on how the RAID is managed and if a
> drive fails, how to replace it and rebuild the array. Some info I
> REALLY need to know before I set one up. =)
> I've found lots of info about what an array does but no real meat on
> managing an array.
> Any pointers of where I can go to find actual how-to's would be
> appreciated.

> I'm pretty comfortable with Fedora Core. But, I'm also looking into
> Slackware since a lot I've found indicates it's a bit (or a lot) more
> stable, secure, and tested.
> So, does the OS handle array management, or software apart from the OS?
> (When I installed a SATA on my own PC I had to install some HD software
> that loads up before the OS does.
> So does picking the OS matter too much when considering RAID?

> And, how hard is it to replace a RAIDed drive?
> If I have a RAID 10 and a drive goes bad, is it as easy as replacing
> the drive and selecting something in a program that "rebuilds the
> array"?
> (How would I know a drive's gone bad anyway? Does the RAID do a
> constant parity check and whatnot and let me know of abnormalities? Or
> do I have to run an FSCK or something now and then?

> Thanks for any feedback and information!
> -Liam

If your data is important enough to you to consider a RAID you should
already have everything on UPS's.  Power quality problems wipe out more
data than anything else.
--
JosephKK
Gegen dummheit kampfen die Gotter Selbst, vergebens.  
--Schiller
 
 
 

Basic RAID concerns and Linux OS

Post by M?ns Rullg?r » Mon, 03 Apr 2006 10:41:36



> If your data is important enough to you to consider a RAID you should
> already have everything on UPS's.  Power quality problems wipe out more
> data than anything else.

That depends a lot on where you are geographically.  In the last five
years or so, I can only remember one power outage, which fortunately
didn't cause me any damage.  During the same time, I have had two hard
drives fail.

This is all in Europe.  I hear the power loss is actually a recurring
thing on the other side of pond.  It's a bit curious that electricity
is both cheaper and more reliable here.

--
M?ns Rullg?rd

 
 
 

Basic RAID concerns and Linux OS

Post by Joseph2 » Tue, 04 Apr 2006 11:09:45




>> If your data is important enough to you to consider a RAID you should
>> already have everything on UPS's.  Power quality problems wipe out more
>> data than anything else.

> That depends a lot on where you are geographically.  In the last five
> years or so, I can only remember one power outage, which fortunately
> didn't cause me any damage.  During the same time, I have had two hard
> drives fail.

> This is all in Europe.  I hear the power loss is actually a recurring
> thing on the other side of pond.  It's a bit curious that electricity
> is both cheaper and more reliable here.

Power quality varies over here geographically, price also varies rather
independently.  Unless i am more mistaken than usual the same holds true
for Europe.  Europe does seem to have less power quality problems, though.
--
JosephKK
Gegen dummheit kampfen die Gotter Selbst, vergebens.  
--Schiller
 
 
 

Basic RAID concerns and Linux OS

Post by Bill Davidse » Wed, 05 Apr 2006 01:45:37



> In our small business, we have to hold onto gigs of data. And sadly,
> disgustingly, we don't have any good backup (periodic DVD burning when
> we can) and the PC holding the info just has a couple of ATA HD's.

> We're needing to put together a file server, and I'm looking into mobos
> that handle RAID 10. From what I can see, that's the best balance of
> efficiency and performance even with the 50% size usage.

> Here're my questions:
> I am finding it hard to find info on how the RAID is managed and if a
> drive fails, how to replace it and rebuild the array. Some info I
> REALLY need to know before I set one up. =)
> I've found lots of info about what an array does but no real meat on
> managing an array.
> Any pointers of where I can go to find actual how-to's would be
> appreciated.

> I'm pretty comfortable with Fedora Core. But, I'm also looking into
> Slackware since a lot I've found indicates it's a bit (or a lot) more
> stable, secure, and tested.
> So, does the OS handle array management, or software apart from the OS?
> (When I installed a SATA on my own PC I had to install some HD software
> that loads up before the OS does.
> So does picking the OS matter too much when considering RAID?

> And, how hard is it to replace a RAIDed drive?
> If I have a RAID 10 and a drive goes bad, is it as easy as replacing
> the drive and selecting something in a program that "rebuilds the
> array"?
> (How would I know a drive's gone bad anyway? Does the RAID do a
> constant parity check and whatnot and let me know of abnormalities? Or
> do I have to run an FSCK or something now and then?

> Thanks for any feedback and information!

I would go out and buy an external enclosure with a few drives and
backup right now.

Then buy the "mdadm" book for education on how it all works. You might
also learn about RAID-6 storage, it will survive the failure of any two
drives, like RAID-10, but needs far fewer drives. For data on N drives,
R10 needs 2*(N+1) and R6 needs N+2. You want a hot spare with either,
and RAID-10 performs better after a two drive failure.

Start climbing the learning curve, people on the net can only provide
places to look.

--
bill davidsen
   SBC/Prodigy Yorktown Heights NY data center
   http://newsgroups.news.prodigy.com

 
 
 

Basic RAID concerns and Linux OS

Post by magnat » Fri, 07 Apr 2006 22:04:09



> In our small business, we have to hold onto gigs of data. And sadly,
> disgustingly, we don't have any good backup (periodic DVD burning when
> we can) and the PC holding the info just has a couple of ATA HD's.

> We're needing to put together a file server, and I'm looking into mobos
> that handle RAID 10. From what I can see, that's the best balance of
> efficiency and performance even with the 50% size usage.

RAID is for getting your data back online *quickly*. If reliability is
more important than speed, you should consider more traditional backups
(like DATs, or just burning DVDs more frequently ...).

Quote:> Here're my questions:
> I am finding it hard to find info on how the RAID is managed and if a
> drive fails, how to replace it and rebuild the array. Some info I
> REALLY need to know before I set one up. =)
> I've found lots of info about what an array does but no real meat on
> managing an array.
> Any pointers of where I can go to find actual how-to's would be
> appreciated.

As others have said, the Linux Documentation Project is your friend.
Beware out-of-date HOWTOs though. There is an important distinction
between software RAID (md) and the Logical Volume Manager (lvm2), and
you should read up on both before deciding exactly what to build on
your disks. (Even more confusingly, you can have LVM2 volumes on md
drives ...)

Quote:> I'm pretty comfortable with Fedora Core. But, I'm also looking into
> Slackware since a lot I've found indicates it's a bit (or a lot) more
> stable, secure, and tested.
> So, does the OS handle array management, or software apart from the OS?
> (When I installed a SATA on my own PC I had to install some HD software
> that loads up before the OS does.
> So does picking the OS matter too much when considering RAID?

I think you're using "OS" to mean "Linux distribution" - if so then no
it shouldn't matter. They should all have the latest versions of md and
lvm2 available. IMHO your choice of distro is all about which package
management system you prefer.

Quote:> And, how hard is it to replace a RAIDed drive?

This is all about the physical configuration of your server, not about
your OS. If you have front-facing hot-swap bays and spare drives handy,
it can be done in seconds.

I confess that I've only ever had two HDs die on me, and neither was in
a RAID array at the time, so I can't give you any views about the
recovery experience. I would hope that rebuilding the array would be
automatic.

CC

 
 
 

Basic RAID concerns and Linux OS

Post by J. Clark » Sat, 08 Apr 2006 02:31:35




>> In our small business, we have to hold onto gigs of data. And sadly,
>> disgustingly, we don't have any good backup (periodic DVD burning when
>> we can) and the PC holding the info just has a couple of ATA HD's.

>> We're needing to put together a file server, and I'm looking into mobos
>> that handle RAID 10. From what I can see, that's the best balance of
>> efficiency and performance even with the 50% size usage.

> RAID is for getting your data back online *quickly*. If reliability is
> more important than speed, you should consider more traditional backups
> (like DATs, or just burning DVDs more frequently ...).

RAID is not for "getting your data back online *quickly*.  It is for not
going offline to begin with.  It is not a substitute for backup.

Quote:>> Here're my questions:
>> I am finding it hard to find info on how the RAID is managed and if a
>> drive fails, how to replace it and rebuild the array. Some info I
>> REALLY need to know before I set one up. =)
>> I've found lots of info about what an array does but no real meat on
>> managing an array.
>> Any pointers of where I can go to find actual how-to's would be
>> appreciated.

> As others have said, the Linux Documentation Project is your friend.
> Beware out-of-date HOWTOs though. There is an important distinction
> between software RAID (md) and the Logical Volume Manager (lvm2), and
> you should read up on both before deciding exactly what to build on
> your disks. (Even more confusingly, you can have LVM2 volumes on md
> drives ...)

>> I'm pretty comfortable with Fedora Core. But, I'm also looking into
>> Slackware since a lot I've found indicates it's a bit (or a lot) more
>> stable, secure, and tested.
>> So, does the OS handle array management, or software apart from the OS?
>> (When I installed a SATA on my own PC I had to install some HD software
>> that loads up before the OS does.
>> So does picking the OS matter too much when considering RAID?

> I think you're using "OS" to mean "Linux distribution" - if so then no
> it shouldn't matter. They should all have the latest versions of md and
> lvm2 available. IMHO your choice of distro is all about which package
> management system you prefer.

>> And, how hard is it to replace a RAIDed drive?

> This is all about the physical configuration of your server, not about
> your OS. If you have front-facing hot-swap bays and spare drives handy,
> it can be done in seconds.

> I confess that I've only ever had two HDs die on me, and neither was in
> a RAID array at the time, so I can't give you any views about the
> recovery experience. I would hope that rebuilding the array would be
> automatic.

> CC

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
 
 
 

Basic RAID concerns and Linux OS

Post by Schraalhans Keukenmeeste » Tue, 18 Apr 2006 17:32:39



> In our small business, we have to hold onto gigs of data. And sadly,
> disgustingly, we don't have any good backup (periodic DVD burning when
> we can) and the PC holding the info just has a couple of ATA HD's.

> We're needing to put together a file server, and I'm looking into mobos
> that handle RAID 10. From what I can see, that's the best balance of
> efficiency and performance even with the 50% size usage.

> Here're my questions:
> I am finding it hard to find info on how the RAID is managed and if a
> drive fails, how to replace it and rebuild the array. Some info I
> REALLY need to know before I set one up. =)
> I've found lots of info about what an array does but no real meat on
> managing an array.
> Any pointers of where I can go to find actual how-to's would be
> appreciated.

> I'm pretty comfortable with Fedora Core. But, I'm also looking into
> Slackware since a lot I've found indicates it's a bit (or a lot) more
> stable, secure, and tested.
> So, does the OS handle array management, or software apart from the OS?
> (When I installed a SATA on my own PC I had to install some HD software
> that loads up before the OS does.
> So does picking the OS matter too much when considering RAID?

> And, how hard is it to replace a RAIDed drive?
> If I have a RAID 10 and a drive goes bad, is it as easy as replacing
> the drive and selecting something in a program that "rebuilds the
> array"?
> (How would I know a drive's gone bad anyway? Does the RAID do a
> constant parity check and whatnot and let me know of abnormalities? Or
> do I have to run an FSCK or something now and then?

> Thanks for any feedback and information!
> -Liam

For reliability, hassle-free operation and a relatively long period of
support on a given release you might consider CentOS as well. An
enterprise-type Linux, freeware. No bleeding edge stuff there. It's not
as * as the popular distros that have updates on a very regular and
frequent basis, but it does the job.

RAID-10 is disk-expensive. RAID6 has the same fault tolerance at lower
costs. And it does not elminate the need for good backups. Fire,
flooding, theft, power spikes, they tend not to limit themselves to a
max of two disks in any array. If the data is critical for business
operation, off-site storage of backups or data-mirroring may even be a
requirement.

A good backup scheme, executed as intended and periodically tested is
still a proven method of keeping your business running after a
'disaster' of many kinds.

And, as stated by others, a properly dimensioned UPS for all your
mission-critical equipment is a wise investment. Data consistency is
important, and sudden power-outs can wreak havoc on your disk contents.
Can, it doesn't always have to be that way. Graceful shutdowns are a
bliss, that extra half hour or so the UPS buys you can save big bucks.

I've had measurements done in my previous company, we had our power
lines monitored for a three-week period continuously and we were a bit
in shock after seeing the reports. The number of (brief, admittedly) but
  HIGH voltage spikes during that period made one thing very clear: we
needed a good UPS for all our servers and networking equipment. And, as
expected, the number of unknown-origin serice failures suddenly dropped
steeply. That was in the Netherlands, where power reliability and
quality is said to be very high.

Since then, I have a UPS at home as well. It's an old one, and by no
means hi-tech, it weighs well over 100kgs and it's huge, noisy, and
ugly, but I am glad I have it. I admit, I got this one for free from a
former employer.
Modern ones come in far smaller housings, are quiet, easier to operate
and integrate better with your gear. And cost a fraction of what your
stuff's worth, let alone your data.

For disk reliability in operating conditions I'd still recommend
SCSI-based storage over IDE anytime. Yes, much more expensive, and much
more reliable too. Plus it leans much less on the cpu in the server.
Especially with multi-client networks to me nothing beats SCSI.

HTH,

Sh.

 
 
 

Basic RAID concerns and Linux OS

Post by dnoye » Wed, 26 Apr 2006 10:48:37


Don't even THINK about software raid or fakeraid for ease of use and/or
data reliability.

A hardware raid is as simple as pop out the old drive, pop in the new
drive, go into computer bios and tell it to rebuild, or wait till OS
starts and use drive too to tell it to rebuild.  no fdisking the drive
to make it compatible or anything like that.

Alternately you can use a hot swappable drive and skip the reboot and
just use the drive's software to rebuild the array.

I just bought a 3ware hardware raid controller and there is no way I
could be happier.  NONE.  yes it costs more.  Sure some say its slower.
  But again, I said if your doing this for safety/ease of use its worth
every penny, and $150 aint much at all.


> In our small business, we have to hold onto gigs of data. And sadly,
> disgustingly, we don't have any good backup (periodic DVD burning when
> we can) and the PC holding the info just has a couple of ATA HD's.

> We're needing to put together a file server, and I'm looking into mobos
> that handle RAID 10. From what I can see, that's the best balance of
> efficiency and performance even with the 50% size usage.

> Here're my questions:
> I am finding it hard to find info on how the RAID is managed and if a
> drive fails, how to replace it and rebuild the array. Some info I
> REALLY need to know before I set one up. =)
> I've found lots of info about what an array does but no real meat on
> managing an array.
> Any pointers of where I can go to find actual how-to's would be
> appreciated.

> I'm pretty comfortable with Fedora Core. But, I'm also looking into
> Slackware since a lot I've found indicates it's a bit (or a lot) more
> stable, secure, and tested.
> So, does the OS handle array management, or software apart from the OS?
> (When I installed a SATA on my own PC I had to install some HD software
> that loads up before the OS does.
> So does picking the OS matter too much when considering RAID?

> And, how hard is it to replace a RAIDed drive?
> If I have a RAID 10 and a drive goes bad, is it as easy as replacing
> the drive and selecting something in a program that "rebuilds the
> array"?
> (How would I know a drive's gone bad anyway? Does the RAID do a
> constant parity check and whatnot and let me know of abnormalities? Or
> do I have to run an FSCK or something now and then?

> Thanks for any feedback and information!
> -Liam

--
Thank you,

"Then said I, Wisdom [is] better than strength: nevertheless the poor
man's wisdom [is] despised, and his words are not heard." Ecclesiastes 9:16

 
 
 

Basic RAID concerns and Linux OS

Post by dnoye » Wed, 26 Apr 2006 10:54:08




>> In our small business, we have to hold onto gigs of data. And sadly,
>> disgustingly, we don't have any good backup (periodic DVD burning when
>> we can) and the PC holding the info just has a couple of ATA HD's.

>> We're needing to put together a file server, and I'm looking into mobos
>> that handle RAID 10. From what I can see, that's the best balance of
>> efficiency and performance even with the 50% size usage.

>> Here're my questions:
>> I am finding it hard to find info on how the RAID is managed and if a
>> drive fails, how to replace it and rebuild the array. Some info I
>> REALLY need to know before I set one up. =)
>> I've found lots of info about what an array does but no real meat on
>> managing an array.
>> Any pointers of where I can go to find actual how-to's would be
>> appreciated.

>> I'm pretty comfortable with Fedora Core. But, I'm also looking into
>> Slackware since a lot I've found indicates it's a bit (or a lot) more
>> stable, secure, and tested.
>> So, does the OS handle array management, or software apart from the OS?
>> (When I installed a SATA on my own PC I had to install some HD software
>> that loads up before the OS does.
>> So does picking the OS matter too much when considering RAID?

>> And, how hard is it to replace a RAIDed drive?
>> If I have a RAID 10 and a drive goes bad, is it as easy as replacing
>> the drive and selecting something in a program that "rebuilds the
>> array"?
>> (How would I know a drive's gone bad anyway? Does the RAID do a
>> constant parity check and whatnot and let me know of abnormalities? Or
>> do I have to run an FSCK or something now and then?

>> Thanks for any feedback and information!
>> -Liam

> For reliability, hassle-free operation and a relatively long period of
> support on a given release you might consider CentOS as well. An
> enterprise-type Linux, freeware. No bleeding edge stuff there. It's not
> as * as the popular distros that have updates on a very regular and
> frequent basis, but it does the job.

> RAID-10 is disk-expensive. RAID6 has the same fault tolerance at lower
> costs. And it does not elminate the need for good backups. Fire,
> flooding, theft, power spikes, they tend not to limit themselves to a
> max of two disks in any array. If the data is critical for business
> operation, off-site storage of backups or data-mirroring may even be a
> requirement.

If your nto storing it off site, i dont even see the point of the
backup.  You can just copy onto a 2nd local computer which is much
faster and easier to manage.

Quote:> A good backup scheme, executed as intended and periodically tested is
> still a proven method of keeping your business running after a
> 'disaster' of many kinds.

> And, as stated by others, a properly dimensioned UPS for all your
> mission-critical equipment is a wise investment. Data consistency is
> important, and sudden power-outs can wreak havoc on your disk contents.
> Can, it doesn't always have to be that way. Graceful shutdowns are a
> bliss, that extra half hour or so the UPS buys you can save big bucks.

yes, and sudden reboots can be just as *.

- Show quoted text -

Quote:> I've had measurements done in my previous company, we had our power
> lines monitored for a three-week period continuously and we were a bit
> in shock after seeing the reports. The number of (brief, admittedly) but
>  HIGH voltage spikes during that period made one thing very clear: we
> needed a good UPS for all our servers and networking equipment. And, as
> expected, the number of unknown-origin serice failures suddenly dropped
> steeply. That was in the Netherlands, where power reliability and
> quality is said to be very high.

> Since then, I have a UPS at home as well. It's an old one, and by no
> means hi-tech, it weighs well over 100kgs and it's huge, noisy, and
> ugly, but I am glad I have it. I admit, I got this one for free from a
> former employer.
> Modern ones come in far smaller housings, are quiet, easier to operate
> and integrate better with your gear. And cost a fraction of what your
> stuff's worth, let alone your data.

> For disk reliability in operating conditions I'd still recommend
> SCSI-based storage over IDE anytime. Yes, much more expensive, and much
> more reliable too. Plus it leans much less on the cpu in the server.
> Especially with multi-client networks to me nothing beats SCSI.

what is more reliable about SCSI over IDE?  SCSI is just an interface
right, the physical media is still the same?

Quote:> HTH,

> Sh.

--
Thank you,

"Then said I, Wisdom [is] better than strength: nevertheless the poor
man's wisdom [is] despised, and his words are not heard." Ecclesiastes 9:16

 
 
 

Basic RAID concerns and Linux OS

Post by J. Clark » Wed, 26 Apr 2006 14:00:08





>>> In our small business, we have to hold onto gigs of data. And sadly,
>>> disgustingly, we don't have any good backup (periodic DVD burning when
>>> we can) and the PC holding the info just has a couple of ATA HD's.

>>> We're needing to put together a file server, and I'm looking into mobos
>>> that handle RAID 10. From what I can see, that's the best balance of
>>> efficiency and performance even with the 50% size usage.

>>> Here're my questions:
>>> I am finding it hard to find info on how the RAID is managed and if a
>>> drive fails, how to replace it and rebuild the array. Some info I
>>> REALLY need to know before I set one up. =)
>>> I've found lots of info about what an array does but no real meat on
>>> managing an array.
>>> Any pointers of where I can go to find actual how-to's would be
>>> appreciated.

>>> I'm pretty comfortable with Fedora Core. But, I'm also looking into
>>> Slackware since a lot I've found indicates it's a bit (or a lot) more
>>> stable, secure, and tested.
>>> So, does the OS handle array management, or software apart from the OS?
>>> (When I installed a SATA on my own PC I had to install some HD software
>>> that loads up before the OS does.
>>> So does picking the OS matter too much when considering RAID?

>>> And, how hard is it to replace a RAIDed drive?
>>> If I have a RAID 10 and a drive goes bad, is it as easy as replacing
>>> the drive and selecting something in a program that "rebuilds the
>>> array"?
>>> (How would I know a drive's gone bad anyway? Does the RAID do a
>>> constant parity check and whatnot and let me know of abnormalities? Or
>>> do I have to run an FSCK or something now and then?

>>> Thanks for any feedback and information!
>>> -Liam

>> For reliability, hassle-free operation and a relatively long period of
>> support on a given release you might consider CentOS as well. An
>> enterprise-type Linux, freeware. No bleeding edge stuff there. It's not
>> as * as the popular distros that have updates on a very regular and
>> frequent basis, but it does the job.

>> RAID-10 is disk-expensive. RAID6 has the same fault tolerance at lower
>> costs. And it does not elminate the need for good backups. Fire,
>> flooding, theft, power spikes, they tend not to limit themselves to a
>> max of two disks in any array. If the data is critical for business
>> operation, off-site storage of backups or data-mirroring may even be a
>> requirement.

> If your nto storing it off site, i dont even see the point of the
> backup.  You can just copy onto a 2nd local computer which is much
> faster and easier to manage.

>> A good backup scheme, executed as intended and periodically tested is
>> still a proven method of keeping your business running after a
>> 'disaster' of many kinds.

>> And, as stated by others, a properly dimensioned UPS for all your
>> mission-critical equipment is a wise investment. Data consistency is
>> important, and sudden power-outs can wreak havoc on your disk contents.
>> Can, it doesn't always have to be that way. Graceful shutdowns are a
>> bliss, that extra half hour or so the UPS buys you can save big bucks.

> yes, and sudden reboots can be just as *.

>> I've had measurements done in my previous company, we had our power
>> lines monitored for a three-week period continuously and we were a bit
>> in shock after seeing the reports. The number of (brief, admittedly) but
>>  HIGH voltage spikes during that period made one thing very clear: we
>> needed a good UPS for all our servers and networking equipment. And, as
>> expected, the number of unknown-origin serice failures suddenly dropped
>> steeply. That was in the Netherlands, where power reliability and
>> quality is said to be very high.

>> Since then, I have a UPS at home as well. It's an old one, and by no
>> means hi-tech, it weighs well over 100kgs and it's huge, noisy, and
>> ugly, but I am glad I have it. I admit, I got this one for free from a
>> former employer.
>> Modern ones come in far smaller housings, are quiet, easier to operate
>> and integrate better with your gear. And cost a fraction of what your
>> stuff's worth, let alone your data.

>> For disk reliability in operating conditions I'd still recommend
>> SCSI-based storage over IDE anytime. Yes, much more expensive, and much
>> more reliable too. Plus it leans much less on the cpu in the server.
>> Especially with multi-client networks to me nothing beats SCSI.

> what is more reliable about SCSI over IDE?  SCSI is just an interface
> right, the physical media is still the same?

Usually not--SCSI drives are targetted at a different market from PATA and
SATA drives and have different mechanical parts as a result.

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)

 
 
 

Basic RAID concerns and Linux OS

Post by Chris Co » Wed, 26 Apr 2006 23:42:03


...

Quote:

> RAID-10 is disk-expensive. RAID6 has the same fault tolerance at lower
> costs. And it does not elminate the need for good backups. Fire,
> flooding, theft, power spikes, they tend not to limit themselves to a
> max of two disks in any array. If the data is critical for business
> operation, off-site storage of backups or data-mirroring may even be a
> requirement.

RAID6 does NOT have the same fault tolerance as RAID10.  Perhaps
you mean the same as RAID0+1??  RAID6 is merely RAID5 with the addition
of a separate stripe alogorithm.  RAID6 will allow for two
drive failures instead of just one.  With RAID10 you can lose
up to half of total amount of drives as long as you don't lose
both halves of a mirrored set of stripes.

The advantage of RAID6 is that the second drive failure can
be any drive.  The disadvantage is on writing speed (same as
or worse than RAID5).

I think RAID6 is a good thing.. certainly a superior replacement
for RAID5, but RAID10 with a good raid controller will be
faster and in large arrays, much more redundant.

I do agree with your statement about the need for backups.

 
 
 

Basic RAID concerns and Linux OS

Post by Bill Davidse » Fri, 28 Apr 2006 01:18:23



>> RAID-10 is disk-expensive. RAID6 has the same fault tolerance at lower
>> costs. And it does not elminate the need for good backups. Fire,
>> flooding, theft, power spikes, they tend not to limit themselves to a
>> max of two disks in any array. If the data is critical for business
>> operation, off-site storage of backups or data-mirroring may even be a
>> requirement.

> If your nto storing it off site, i dont even see the point of the
> backup.  You can just copy onto a 2nd local computer which is much
> faster and easier to manage.

Yes, if your data is non-critical and you don't need a backup you can
put a copy on another local computer.

--
bill davidsen
   SBC/Prodigy Yorktown Heights NY data center
   http://newsgroups.news.prodigy.com