Seeking Backup advice RAID vs Tape

Seeking Backup advice RAID vs Tape

Post by Scott Hepple » Sun, 10 Mar 2002 16:56:40



I am in the planning stages of a new system.   Are there any advantages
to going with two 40Gb drives vs.  one 80Gb?  I saw mention of
partitioning the swap space across both drives but that was in an  dual
CPU system.

I am considering putting my finances on gnucash and would like to be
able to back up the new system.
What are the considerations of tape drive backup vs 2 HDD RAID vs 2 HDD
non RAID w/ USR partition

All advice apprecieated

Scott

 
 
 

Seeking Backup advice RAID vs Tape

Post by Dragan Cola » Sun, 10 Mar 2002 18:04:01



> I am in the planning stages of a new system.   Are there any advantages
> to going with two 40Gb drives vs.  one 80Gb?  I saw mention of
> partitioning the swap space across both drives but that was in an  dual
> CPU system.

> I am considering putting my finances on gnucash and would like to be
> able to back up the new system.
> What are the considerations of tape drive backup vs 2 HDD RAID vs 2 HDD
> non RAID w/ USR partition

> All advice apprecieated

> Scott

RAID is a fail-safe system, it's not meant for backups. So even running a
RAID system won't save you from doing tape backups.

Advantages/Disadvantages of RAID:

RAID 0 - Data Striping
       - no fail-safe functionality at all, but it gives
         you a higher performance on sequential read/write of large files
       - 2x40 GByte striped = 80 GByte capacity

RAID 1 - Disk Mirroring (when both drives are on one channel)
       - Disk Duplexing (when each drive is on a separate channel)
       - you have two disks with exactly the same content, that's a very
         expensive solution because you lose half of your capacity but if
         one drive goes down you can work with the other without any data
         loss
       - 2x40 GByte mirrored = 40 GByte capacity

All the other RAID levels require three or more disks and are of no use
with your two disks system.

I'd suggest to do data striping with tape backup. That's how I do it here.

Dragan

 
 
 

Seeking Backup advice RAID vs Tape

Post by Hostile 1 » Mon, 11 Mar 2002 15:00:15



> I am in the planning stages of a new system.   Are there any advantages
> to going with two 40Gb drives vs.  one 80Gb?

Two drives can be faster, depending on what you're doing.  Having multiple
drives does for I/O what multiple CPUs do for processing.  Also you
remove a single point of failure by having only a single drive.

Quote:> I saw mention of partitioning the swap space across both drives but
> that was in an dual CPU system.

Yes, spreading swap across multiple spindles is a good thing to do
regardless of the number of CPUs in the system.  However care must be
taken to do this intelligently.  For example, to get the best benefit
from doing this, with IDE drives, each drive needs to be on its own
channel.  You would not want both drives on the same IDE channel.  

Quote:> What are the considerations of tape drive backup vs 2 HDD RAID vs 2 HDD
> non RAID w/ USR partition

RAID can be best thought of as means of providing fault tolerance, but
it's not really a way to back-up data.  RAID gives you the ability to
deal with hardware failure.  While a tape backup system gives you the
ability to restore your data if all of it is destroyed or deleted.
With a tape archive, you can also arrange to have it stored off site.
With RAID, it doesn't matter how many drives are in it if the whole
machine is destroyed--the data will be gone unless a copy of it exists
outside of the system.

How to proceed depends on how much money you want to spend and how
secure you need to be.  If you've got the money, do both RAID and
establish a back/restore system.  If you don't have the money, ask
yourself how important is your data, and can you afford to lose it
completely?  As for myself, when in the postition of having limited
funds, I'd opt for the tape back-up over RAID.

 
 
 

Seeking Backup advice RAID vs Tape

Post by Christopher Brown » Mon, 11 Mar 2002 15:26:22



> I am in the planning stages of a new system.   Are there any advantages
> to going with two 40Gb drives vs.  one 80Gb?  I saw mention of
> partitioning the swap space across both drives but that was in an  dual
> CPU system.

> I am considering putting my finances on gnucash and would like to be
> able to back up the new system.
> What are the considerations of tape drive backup vs 2 HDD RAID vs 2 HDD
> non RAID w/ USR partition

You seem to be falling into the fallacy that RAID has anything to with
system backups.

Reality is that it does not.

RAID _may_, depending on which level you go with, provide some
redundancy, but only within the box that you put the two drives in.

Two notable things that are utterly unaffected:
- If your house burns down, RAID provides no backup.
- If you delete a file by accident, RAID provides no backup.

A _real_ backup needs to get taken out of your computer system.

You could conceivably do this with a second drive, if you periodically
mirror to the drive, and then remove the drive (having it in a $25
"removable bay" would be a good idea).

Of course, if you just have one spare drive for that, you only have
one single backup, which may not suffice.

I would instead point to RAID as a way of potentially improving
performance quite a bit, and improving reliability a _little_ bit (if
one drive fails, you might have a "mirror" left alive), whilst looking
at other approaches for actually backing up your data.
--

http://www3.sympatico.ca/cbbrowne/backup.html
Rules of the Evil Overlord  #62. "I will design fortress hallways with
no alcoves or protruding structural supports which intruders could use
for cover in a firefight." <http://www.eviloverlord.com/>

 
 
 

1. Using a RAID box for innd news spools -- advice sought

Hi all,

Anyone have experience running news with RAID spools?

I'm moving my news server from an underpowered Sparc 10 to a new Ultra
with lots of RAID disk.  For news, is it better to build multiple small
partitions for the spool (as is the only available case when using
quad-packs and other non-RAID disk technologies), or is it better to build
a single large partition of say 16GB for the spool?  Or does it matter one
way or the other?  

Thanx,
Rob
--

      _ _ _ _           _    _ _ _ _ _  
     /\_\_\_\_\        /\_\ /\_\_\_\_\_\  
    /\/_/_/_/_/       /\/_/ \/_/_/_/_/_/  Robert J. Tanner
   /\/_/__\/_/ __    /\/_/    /\/_/       CCF System Administration
  /\/_/_/_/_/ /\_\  /\/_/    /\/_/        NASA Ames Research Center
 /\/_/ \/_/  /\/_/_/\/_/    /\/_/         (415) 604-1008

 ____________________________________________________________________

2. 4 Node Cluster..

3. Seeking advice: ATA RAID configuration

4. APM under FreeBSD

5. RAID newbie seeks advice

6. Installing FREEBSD

7. Network backup devices [Advice sought]

8. Linux Window under OS/2?

9. Advice sought: BACKUP SOFTWARE

10. Advice sought: global zone pkgs vs. local zone pkgs

11. Want LINUX for tape drive compatibility. Advice sought

12. Seeking DAT Tape for x86 advice?

13. Seeking advice/opinions about Conner TS4000 tape drive