SATA RAID with HDs in separate box?

SATA RAID with HDs in separate box?

Post by ow » Thu, 26 Aug 2004 03:10:07



Hi,

I'd like to clarify for myself how one could setup a software (SATA) RAID-5
system where HDs are located in a separate box. Suppose I have 1 linux box
that's running a db server and db files are stored on RAID. I could put all HDs
used by RAID in this db server box, connect them to the HD controller and that's
it. However, I'd like to put all RAID HDs in a separate box.

One way I think it could be done if I setup the 2nd linux box (with motherboard,
HD controller, etc) just to run RAID. Then I would connect db server and RAID
server through LAN. The downside of this approach is a lot of overhead (extra
motherboard, RAM, linux setup, LAN overhead, etc).

The second approach I see is to have HD controller located in the db server box,
+ SATA, + long SATA data cables. The problem with this approach is that db
server and RAID server/box should be fairly close; the longest SATA cables I've
found were 3ft.

Any ideas? Thanks

P.S. I know there are ready commercial solutions for this but I'm still
interested in the "do-it-yourself" approach.

 
 
 

SATA RAID with HDs in separate box?

Post by Georg Ach » Thu, 26 Aug 2004 05:55:26



>Hi,

>I'd like to clarify for myself how one could setup a software (SATA) RAID-5
>system where HDs are located in a separate box. Suppose I have 1 linux box
>that's running a db server and db files are stored on RAID. I could put all HDs
>used by RAID in this db server box, connect them to the HD controller and that's
>it. However, I'd like to put all RAID HDs in a separate box.

Why do you want that? There are nice cases available. Have a look at Chenbro
(RM...), they have 19" rack cases with enough place for the mainboard and 6-20
hot swapable SATA drive bays (eg. 16 in the RM414xx).

http://www.chenbro.com.tw/product/cd-racklist.jsp
--

         http://wwwbode.in.tum.de/~acher
         "Oh no, not again !" The bowl of petunias

 
 
 

SATA RAID with HDs in separate box?

Post by ow » Thu, 26 Aug 2004 07:07:05



> Why do you want that? There are nice cases available.

Well, think about db server upgrade for example. If db server and RAID HDs are
in different boxes then you have a lot more flexibility when it comes to how you
do the upgrade. You may build a totally new db server box and then connect the
RAID storage to it. If it something does not go as planned you can always
connect RAID back to the old db server.
 
 
 

SATA RAID with HDs in separate box?

Post by Georg Ach » Thu, 26 Aug 2004 22:39:37




>> Why do you want that? There are nice cases available.

>Well, think about db server upgrade for example. If db server and RAID HDs are
>in different boxes then you have a lot more flexibility when it comes to how you
>do the upgrade. You may build a totally new db server box and then connect the
>RAID storage to it. If it something does not go as planned you can always
>connect RAID back to the old db server.

Then SATA is not usable (50cm cables are even to short for some in-case mounting,
1m (6ft) doesn't help much for external connections to a backplane). If you want
something reliable (electrically and menchanically), the alternatives for
external storage are SCSI or fiber-channel. But both are not really
"cost-effective"...

--

         http://wwwbode.in.tum.de/~acher
         "Oh no, not again !" The bowl of petunias

 
 
 

SATA RAID with HDs in separate box?

Post by Dave » Fri, 27 Aug 2004 01:31:10




> > Why do you want that? There are nice cases available.

> Well, think about db server upgrade for example. If db server and RAID HDs
are
> in different boxes then you have a lot more flexibility when it comes to
how you
> do the upgrade. You may build a totally new db server box and then connect
the
> RAID storage to it. If it something does not go as planned you can always
> connect RAID back to the old db server.

If you want physical separation, then SATA is probably not your answer...
LVD SCSI, with it's 3m cable length, would probably be more appropriate.  I
don't think that the cost for setting up SCSI vs. SATA should be that
different.  I configured a setup such as that which you describe... I put
the 6 Ultra160 drives into an old PC enclosure with 350W power supply and
connected it to my linux server and used s/w RAID to set up a 5-drive RAID-5
array with one hot spare.  I bought the lot of 6 36Gb drives off of eBay for
$200, the card (also eBay) was $45.  Ribbon cable was $65, hard to find with
enough connectors...
 
 
 

SATA RAID with HDs in separate box?

Post by John-Paul Stewar » Fri, 27 Aug 2004 03:06:09






>>>Why do you want that? There are nice cases available.

>>Well, think about db server upgrade for example. If db server and RAID HDs are
>>in different boxes then you have a lot more flexibility when it comes to how you
>>do the upgrade. You may build a totally new db server box and then connect the
>>RAID storage to it. If it something does not go as planned you can always
>>connect RAID back to the old db server.

> If you want physical separation, then SATA is probably not your answer...
> LVD SCSI, with it's 3m cable length, would probably be more appropriate.  I

Actually, the 3m cable length applied to pre-LVD SCSI busses.  With LVD
you can use up to 12m cables.

Quote:> don't think that the cost for setting up SCSI vs. SATA should be that
> different.  I configured a setup such as that which you describe... I put
> the 6 Ultra160 drives into an old PC enclosure with 350W power supply and
> connected it to my linux server and used s/w RAID to set up a 5-drive RAID-5
> array with one hot spare.  I bought the lot of 6 36Gb drives off of eBay for
> $200, the card (also eBay) was $45.  Ribbon cable was $65, hard to find with
> enough connectors...

If you need large amounts of storage, the equation changes dramatically
in favour of using SATA drives.  Compare the price of a 146GB SCSI drive
to the price of, say, a 200GB SATA drive.  Around here the SCSI drive is
about 4 times the price of the SATA drive.  (Also, in many business
environments, buying unsupported gear from E-Bay simply isn't viable.)

Some high-end external RAID enclosures use LVD SCSI (or FibreChannel)
for connection to the host system and SATA for the drives.  Those
enclosures are *very* expensive, though, as they must include the RAID
controller (plus some sort of configuration interface for the RAID) as
well as the circuitry for the SATA drives and the SCSI host connection.
  (See, for example, the NexSan ATABoy series.)

AIUI, the OP was looking to duplicate such an item:  an external RAID
box using low-cost SATA drives.  Without the SCSI-to-SATA RAID
controller found in those boxes, a do-it-yourself solution just isn't
practical, though.

 
 
 

SATA RAID with HDs in separate box?

Post by ow » Fri, 27 Aug 2004 07:41:30



> AIUI, the OP was looking to duplicate such an item:  an external RAID
> box using low-cost SATA drives.  Without the SCSI-to-SATA RAID
> controller found in those boxes, a do-it-yourself solution just isn't
> practical, though.

... and SCSI-to-SATA RAID controller is a proprietary item included with the
system, is it not? I briefly looked and found a bunch of SCSI-to-SATA RAID
*systems* but no controllers (was not looking too hard though).
 
 
 

SATA RAID with HDs in separate box?

Post by John-Paul Stewar » Sat, 28 Aug 2004 00:12:12




>> AIUI, the OP was looking to duplicate such an item:  an external RAID
>> box using low-cost SATA drives.  Without the SCSI-to-SATA RAID
>> controller found in those boxes, a do-it-yourself solution just isn't
>> practical, though.

> ... and SCSI-to-SATA RAID controller is a proprietary item included with
> the system, is it not? I briefly looked and found a bunch of
> SCSI-to-SATA RAID *systems* but no controllers (was not looking too hard
> though).

That's my understanding too.
 
 
 

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