Обсуждение: How to choose a disc array for Postgresql?

I am moving our small business application
database application supporting
a 24/7 animal hospital to use 8.0.15 from
7.4.19 (it will not support 8.1, 8.2. or 8.3).

Now, we can choose a new a disc array. SATA
seems cheaper and you can get more discs but
I want to stay with SCSI.  Any good reasons to
choose SATA over SCSI?

I need to consider a vendor for the new disc array (6-
to 8 discs). The local vendor (in the San Francisco Bay Area),
I've not been completely pleased with, so I am considering using
Dell storage connecting to an retail version LSI MegaRAID 320-2X card.

Anyone use any vendors that have been supportive of Postgresql?

Thanks for your help/feedback.

Steve

On Sat, 1 Mar 2008 23:37:37 -0800
"Steve Poe" <steve.poe@gmail.com> wrote:

> I am moving our small business application
> database application supporting
> a 24/7 animal hospital to use 8.0.15 from
> 7.4.19 (it will not support 8.1, 8.2. or 8.3).
>
> Now, we can choose a new a disc array. SATA
> seems cheaper and you can get more discs but
> I want to stay with SCSI.  Any good reasons to
> choose SATA over SCSI?

Sata is great if you need lots of space. SCSI/SAS is better if you want
lots of performance from a lesser amount of spindles.

Joshua D. Drake

--
The PostgreSQL Company since 1997: http://www.commandprompt.com/
PostgreSQL Community Conference: http://www.postgresqlconference.org/
Donate to the PostgreSQL Project: http://www.postgresql.org/about/donate
PostgreSQL SPI Liaison | SPI Director |  PostgreSQL political pundit

The Dell MD1000 is good.  The most trouble you will have will be with the raid adapter - to get the best support I suggest trying to buy the dell perc 5e (also an LSI) - that way you'll get drivers that work and are supported.

Latest seq scan performance I've seen on redhat 5 is 400 MB/s on eight drives in RAID10 after setting linux max readahead to 16384 (blockdev --setra 16384) and 220 without.

----- Original Message -----
From: pgsql-performance-owner@postgresql.org <pgsql-performance-owner@postgresql.org>
To: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Sent: Sun Mar 02 02:37:37 2008
Subject: [PERFORM] How to choose a disc array for Postgresql?

I am moving our small business application
database application supporting
a 24/7 animal hospital to use 8.0.15 from
7.4.19 (it will not support 8.1, 8.2. or 8.3).

Now, we can choose a new a disc array. SATA
seems cheaper and you can get more discs but
I want to stay with SCSI.  Any good reasons to
choose SATA over SCSI?

I need to consider a vendor for the new disc array (6-
to 8 discs). The local vendor (in the San Francisco Bay Area),
I've not been completely pleased with, so I am considering using
Dell storage connecting to an retail version LSI MegaRAID 320-2X card.

Anyone use any vendors that have been supportive of Postgresql?

Thanks for your help/feedback.

Steve

On Mar 2, 2008, at 2:37 AM, Steve Poe wrote:

> I need to consider a vendor for the new disc array (6-
> to 8 discs). The local vendor (in the San Francisco Bay Area),
> I've not been completely pleased with, so I am considering using
> Dell storage connecting to an retail version LSI MegaRAID 320-2X card.
>
> Anyone use any vendors that have been supportive of Postgresql?

I've been 1000% satisfied with Partners Data for my RAID systems.  I
connect to the host boxes with a fibre channel.  They've gone above
and beyond expectations for supporting my FreeBSD systems.  I don't
know if/how they support postgres as I never asked for that help.
Their prices are excellent, too.

As for your plan to hook up Dell storage to a 320-2x card, the last
time I did that, the lsi card complained that one of the drives in the
14-disk chassis was down.  Identical on two different arrays I had.
Dell swapped nearly every single part, yet the LSI card still
complained.  I had to drop the drives to U160 speed to get it to even
recognize all the drives.

I hooked up the same arrays to Adaptec controllers, and they seemed to
not mind the array so much, but would cause random failures
(catastrophic failures resulting in loss of all data) on occassion
until I dropped the disks to U160 speed.   Dell swears up and down
that their devices work at U320, but the two arrays I got from them,
which were identical twins, both clearly did not work at U320 properly.

It is these Dell arrays that I replaced with the Partners Data units
last year.  The dell boxes still have a  year of warrantee on them...
anyone interested in buying them from me, please make an offer :-)

Vivek,

I've had the same issue with the LSI MegaRAID card previously, I had
to drop to U160. Since it happened with a brand new card and
the local vendor's disc array, I've blamed the local vendor since this
happened before.

On Sun, 2 Mar 2008 20:02:36 -0800
"Steve Poe" <steve.poe@gmail.com> wrote:

> > It is these Dell arrays that I replaced with the Partners Data units
> > last year.  The dell boxes still have a  year of warrantee on
> > them... anyone interested in buying them from me, please make an
> > offer :-)

I suggest the HP 64* and P* series.

Joshua D. Drake


--
The PostgreSQL Company since 1997: http://www.commandprompt.com/
PostgreSQL Community Conference: http://www.postgresqlconference.org/
Donate to the PostgreSQL Project: http://www.postgresql.org/about/donate
PostgreSQL SPI Liaison | SPI Director |  PostgreSQL political pundit

On Sun, Mar 2, 2008 at 9:11 PM, Vivek Khera <vivek@khera.org> wrote:
>
>  On Mar 2, 2008, at 2:37 AM, Steve Poe wrote:
>
>  > I need to consider a vendor for the new disc array (6-
>  > to 8 discs). The local vendor (in the San Francisco Bay Area),
>  > I've not been completely pleased with, so I am considering using
>  > Dell storage connecting to an retail version LSI MegaRAID 320-2X card.
>  >
>  > Anyone use any vendors that have been supportive of Postgresql?
>
>  I've been 1000% satisfied with Partners Data for my RAID systems.  I
>  connect to the host boxes with a fibre channel.  They've gone above
>  and beyond expectations for supporting my FreeBSD systems.  I don't
>  know if/how they support postgres as I never asked for that help.
>  Their prices are excellent, too.
>
>  As for your plan to hook up Dell storage to a 320-2x card, the last
>  time I did that, the lsi card complained that one of the drives in the
>  14-disk chassis was down.  Identical on two different arrays I had.
>  Dell swapped nearly every single part, yet the LSI card still
>  complained.  I had to drop the drives to U160 speed to get it to even
>  recognize all the drives.

Is there still some advantage to U320 over SAS?  I'm just wondering
why one would be building a new machine with U320 instead of SAS
nowadays.

And I've never had any of the problems you list with LSI cards.  The
only issue I've seen is mediocre RAID-10 performance on their cards
many years ago, when I was testing them for our database server.
Adaptec controllers, especially RAID controllers have been nothing but
problematic for me, with random lockups every month or two.  Just
enough to make it really dangerous, not often enough to make it easy
to troubleshoot.  In those systems the lockup problems were solved
100% by switching to LSI based controllers.

On Sat, 1 Mar 2008, Steve Poe wrote:

> SATA seems cheaper and you can get more discs but I want to stay with
> SCSI.  Any good reasons to choose SATA over SCSI?

I've collected up many of the past list comments on this subject and put a
summary at http://www.postgresqldocs.org/index.php/SCSI_vs._IDE/SATA_Disks

--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD

On Mar 2, 2008, at 11:02 PM, Steve Poe wrote:

> It seems the RAID card manufacturers have more to do with failures
> than the drives themselves. Have you found a RAID card you did not
> have to drop to U160?

The only array for which I've had to drop to U160 on an LSI card is
the Dell array.  I think the backplane is not fully U320 compliant,
but I have no real proof.  I had the same seagate drives, which I
*know* work U320 with an LSI card.

It seems only the Dell-branded LSI cards work with the Dell-branded
arrays at U320 -- at least they report to be working.

Because I'm leery of Adaptec, and the LSI cards are hard to get decent
arrays at decent prices, I've moved to using external RAID enclosures
attached via LSI Fibre Channel cards.

On Mar 2, 2008, at 11:23 PM, Scott Marlowe wrote:

> And I've never had any of the problems you list with LSI cards.  The
> only issue I've seen is mediocre RAID-10 performance on their cards

I don't fault the LSI card.  The 320-2X is by far one of the fastest
cards I've ever used, and the most stable under FreeBSD.  The only
time I've had issue with the LSI cards is with dell-branded disk
enclosures.

As for using U320 vs. SAS, I guess the decision would be based on
cost.  The last systems I bought with big disks were over a year ago,
so I don't know the pricing anymore.

On Mar 3, 2008, at 12:16 AM, Greg Smith wrote:

> I've collected up many of the past list comments on this subject and
> put a summary athttp://www.postgresqldocs.org/index.php/SCSI_vs._IDE/SATA_Disks

I'll add a recommendation of Partners Data Systems http://www.partnersdata.com/
  as a great vendor of SATA RAID subsystems (the 16-disk units I have
are based on an Areca controller and have dual FC output)

Greg Smith wrote:
> On Sat, 1 Mar 2008, Steve Poe wrote:
>> SATA over SCSI?
>
> I've collected up many of the past list comments on this subject and put
> a summary at
> http://www.postgresqldocs.org/index.php/SCSI_vs._IDE/SATA_Disks

Should this section:

  ATA Disks... Always default to the write cache
  enabled....turn it off....

be amended to say that if you have an OS that supports write
barriers (linuxes newer than early 2005) you shouldn't worry
about this?

And perhaps the SCSI section should also be amended to say that
that the same 2.6 kernels that fail to send the IDE FLUSH CACHE
command also fail to send the SCSI SYNCHRONIZE CACHE command,
so you should go through the same cache-disabling hoops there?


References from the Linux SATA driver guy and lwn here:
http://hardware.slashdot.org/comments.pl?sid=149349&cid=12519114
http://lwn.net/Articles/77074/