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* Advice on RAID card
@ 2005-09-24 08:34 PFC <lists@boutiquenumerique.com>
0 siblings, 1 reply; 18+ messages in thread
From: PFC @ 2005-09-24 08:34 UTC (permalink / raw)
To: pgsql-performance
Hello fellow Postgresql'ers.
I've been stumbled on this RAID card which looks nice. It is a PCI-X SATA
Raid card with 6 channels, and does RAID 0,1,5,10,50.
It is a HP card with an Adaptec chip on it, and 64 MB cache.
HP Part # : 372953-B21
Adaptec Part # : AAR-2610SA/64MB/HP
There' even a picture :
http://megbytes.free.fr/Sata/DSC05970.JPG
I know it isn't as good as a full SCSI system. I just want to know if
some of you have had experiences with these, and if this cards belong to
the "slower than no RAID" camp, like some DELL card we often see mentioned
here, or to the "decent performance for the price" camp. It is to run on a
Linux.
Thanks in advance for your time and information.
^ permalink raw reply [nested|flat] 18+ messages in thread
* Re: Advice on RAID card
@ 2005-09-24 15:55 Ron Peacetree <rjpeace@earthlink.net>
0 siblings, 1 reply; 18+ messages in thread
From: Ron Peacetree @ 2005-09-24 15:55 UTC (permalink / raw)
To: PFC <lists@boutiquenumerique.com>; pgsql-performance
It looks like a rebranded low end Adaptec 64MB PCI-X <-> SATA RAID card.
Looks like the 64MB buffer is not upgradable.
Looks like it's SATA, not SATA II
There are much better ways to spend your money.
These are the products with the current best price/performance ratio:
http://www.areca.us/products/html/pcix-sata.htm
Assuming you are not building 1U boxes, get one of the full height
cards and order it with the maximum size buffer you can afford.
The cards take 1 SODIMM, so that will be a max of 1GB or 2GB
depending on whether 2GB SODIMMs are available to you yet.
Ron
-----Original Message-----
From: PFC <lists@boutiquenumerique.com>
Sent: Sep 24, 2005 4:34 AM
To: pgsql-performance@postgresql.org
Subject: [PERFORM] Advice on RAID card
Hello fellow Postgresql'ers.
I've been stumbled on this RAID card which looks nice. It is a PCI-X SATA
Raid card with 6 channels, and does RAID 0,1,5,10,50.
It is a HP card with an Adaptec chip on it, and 64 MB cache.
HP Part # : 372953-B21
Adaptec Part # : AAR-2610SA/64MB/HP
There' even a picture :
http://megbytes.free.fr/Sata/DSC05970.JPG
I know it isn't as good as a full SCSI system. I just want to know if
some of you have had experiences with these, and if this cards belong to
the "slower than no RAID" camp, like some DELL card we often see mentioned
here, or to the "decent performance for the price" camp. It is to run on a
Linux.
Thanks in advance for your time and information.
---------------------------(end of broadcast)---------------------------
TIP 4: Have you searched our list archives?
http://archives.postgresql.org
^ permalink raw reply [nested|flat] 18+ messages in thread
* Re: Advice on RAID card
@ 2005-09-24 16:27 PFC <lists@boutiquenumerique.com>
parent: Ron Peacetree <rjpeace@earthlink.net>
0 siblings, 0 replies; 18+ messages in thread
From: PFC @ 2005-09-24 16:27 UTC (permalink / raw)
To: Ron Peacetree <rjpeace@earthlink.net>; pgsql-performance
> It looks like a rebranded low end Adaptec 64MB PCI-X <-> SATA RAID card.
> Looks like the 64MB buffer is not upgradable.
> Looks like it's SATA, not SATA II
Yeah, that's exactly what it is. I can get one for 150 Euro, the Areca is
at least 600. This is for a budget server so while it would be nice to
have all the high-tech stuff, it's not the point. My question was raher,
is it one of the crap RAID5 cards which are actually SLOWER than plain IDE
disks, or is it decent, even though low-end (and cheap), and worth it
compared to software RAID5 ?
> Assuming you are not building 1U boxes, get one of the full height
> cards and order it with the maximum size buffer you can afford.
> The cards take 1 SODIMM, so that will be a max of 1GB or 2GB
> depending on whether 2GB SODIMMs are available to you yet.
It's for a budget dev server which should have RAID5 for reliability, but
not necessarily stellar performance (and price). I asked about this card
because I can get one at a good price.
Thanks for taking the time to answer.
^ permalink raw reply [nested|flat] 18+ messages in thread
* Re: Advice on RAID card
@ 2005-09-25 10:17 Michael Ben-Nes <miki@canaan.co.il>
parent: PFC <lists@boutiquenumerique.com>
0 siblings, 1 reply; 18+ messages in thread
From: Michael Ben-Nes @ 2005-09-25 10:17 UTC (permalink / raw)
To: PFC <lists@boutiquenumerique.com>; +Cc: pgsql-performance
I would consider Software Raid
PFC wrote:
>
> Hello fellow Postgresql'ers.
>
> I've been stumbled on this RAID card which looks nice. It is a
> PCI-X SATA Raid card with 6 channels, and does RAID 0,1,5,10,50.
> It is a HP card with an Adaptec chip on it, and 64 MB cache.
>
> HP Part # : 372953-B21
> Adaptec Part # : AAR-2610SA/64MB/HP
>
> There' even a picture :
> http://megbytes.free.fr/Sata/DSC05970.JPG
>
> I know it isn't as good as a full SCSI system. I just want to know
> if some of you have had experiences with these, and if this cards
> belong to the "slower than no RAID" camp, like some DELL card we
> often see mentioned here, or to the "decent performance for the
> price" camp. It is to run on a Linux.
>
> Thanks in advance for your time and information.
>
> ---------------------------(end of broadcast)---------------------------
> TIP 4: Have you searched our list archives?
>
> http://archives.postgresql.org
--
--------------------------
Canaan Surfing Ltd.
Internet Service Providers
Ben-Nes Michael - Manager
Tel: 972-4-6991122
Cel: 972-52-8555757
Fax: 972-4-6990098
http://www.canaan.net.il
--------------------------
^ permalink raw reply [nested|flat] 18+ messages in thread
* Re: Advice on RAID card
@ 2005-09-25 14:57 Dave Cramer <pg@fastcrypt.com>
parent: Michael Ben-Nes <miki@canaan.co.il>
0 siblings, 3 replies; 18+ messages in thread
From: Dave Cramer @ 2005-09-25 14:57 UTC (permalink / raw)
To: Michael Ben-Nes <miki@canaan.co.il>; +Cc: PFC <lists@boutiquenumerique.com>; pgsql-performance
I would think software raid would be quite inappropriate considering
postgres when it is working is taking a fair amount of CPU as would
software RAID. Does anyone know if this is really the case ?
Dave
On 25-Sep-05, at 6:17 AM, Michael Ben-Nes wrote:
> I would consider Software Raid
>
>
> PFC wrote:
>
>
>>
>> Hello fellow Postgresql'ers.
>>
>> I've been stumbled on this RAID card which looks nice. It is a
>> PCI-X SATA Raid card with 6 channels, and does RAID 0,1,5,10,50.
>> It is a HP card with an Adaptec chip on it, and 64 MB cache.
>>
>> HP Part # : 372953-B21
>> Adaptec Part # : AAR-2610SA/64MB/HP
>>
>> There' even a picture :
>> http://megbytes.free.fr/Sata/DSC05970.JPG
>>
>> I know it isn't as good as a full SCSI system. I just want to
>> know if some of you have had experiences with these, and if this
>> cards belong to the "slower than no RAID" camp, like some DELL
>> card we often see mentioned here, or to the "decent performance
>> for the price" camp. It is to run on a Linux.
>>
>> Thanks in advance for your time and information.
>>
>> ---------------------------(end of
>> broadcast)---------------------------
>> TIP 4: Have you searched our list archives?
>>
>> http://archives.postgresql.org
>>
>
>
> --
> --------------------------
> Canaan Surfing Ltd.
> Internet Service Providers
> Ben-Nes Michael - Manager
> Tel: 972-4-6991122
> Cel: 972-52-8555757
> Fax: 972-4-6990098
> http://www.canaan.net.il
> --------------------------
>
>
> ---------------------------(end of
> broadcast)---------------------------
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> choose an index scan if your joining column's datatypes do not
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^ permalink raw reply [nested|flat] 18+ messages in thread
* Re: Advice on RAID card
@ 2005-09-25 15:27 Mike Rylander <mrylander@gmail.com>
parent: Dave Cramer <pg@fastcrypt.com>
2 siblings, 0 replies; 18+ messages in thread
From: Mike Rylander @ 2005-09-25 15:27 UTC (permalink / raw)
To: pgsql-performance
On 9/25/05, Dave Cramer <pg@fastcrypt.com> wrote:
> I would think software raid would be quite inappropriate considering
> postgres when it is working is taking a fair amount of CPU as would
> software RAID. Does anyone know if this is really the case ?
>
I attempted to get some extra speed out of my Compaq/HP SA6404 card by
using software RAID1 across to hardware RAID10 sets. It didn't help,
but there was no noticeable load or drop in performance because of it.
Granted, this was on a 4-way Opteron, but, anecdotally speaking, the
linux software RAID has surprisingly low overhead.
My $0.02, hope it helps.
--
Mike Rylander
mrylander@gmail.com
GPLS -- PINES Development
Database Developer
http://open-ils.org
^ permalink raw reply [nested|flat] 18+ messages in thread
* Re: Advice on RAID card
@ 2005-09-25 15:42 Joshua D. Drake <jd@commandprompt.com>
parent: Dave Cramer <pg@fastcrypt.com>
2 siblings, 1 reply; 18+ messages in thread
From: Joshua D. Drake @ 2005-09-25 15:42 UTC (permalink / raw)
To: Dave Cramer <pg@fastcrypt.com>; +Cc: Michael Ben-Nes <miki@canaan.co.il>; PFC <lists@boutiquenumerique.com>; pgsql-performance
Dave Cramer wrote:
> I would think software raid would be quite inappropriate considering
> postgres when it is working is taking a fair amount of CPU as would
> software RAID. Does anyone know if this is really the case ?
The common explanation is that CPUs are so fast now that it doesn't make
a difference.
From my experience software raid works very, very well. However I have
never put
software raid on anything that is very heavily loaded.
I would still use hardware raid if it is very heavily loaded.
Sincerely,
Joshua D. Drake
--
Your PostgreSQL solutions company - Command Prompt, Inc. 1.800.492.2240
PostgreSQL Replication, Consulting, Custom Programming, 24x7 support
Managed Services, Shared and Dedicated Hosting
Co-Authors: plPHP, plPerlNG - http://www.commandprompt.com/
^ permalink raw reply [nested|flat] 18+ messages in thread
* Re: Advice on RAID card
@ 2005-09-25 15:59 Michael Stone <mstone+postgres@mathom.us>
parent: Dave Cramer <pg@fastcrypt.com>
2 siblings, 0 replies; 18+ messages in thread
From: Michael Stone @ 2005-09-25 15:59 UTC (permalink / raw)
To: pgsql-performance
On Sun, Sep 25, 2005 at 10:57:56AM -0400, Dave Cramer wrote:
>I would think software raid would be quite inappropriate considering
>postgres when it is working is taking a fair amount of CPU as would
>software RAID. Does anyone know if this is really the case ?
It's not. Modern cpu's can handle raid operations without even noticing.
At the point where your raid ops become a significant fraction of the
cpu you'll be i/o bound anyway.
Mike Stone
^ permalink raw reply [nested|flat] 18+ messages in thread
* Re: Advice on RAID card
@ 2005-09-25 16:08 PFC <lists@boutiquenumerique.com>
parent: Joshua D. Drake <jd@commandprompt.com>
0 siblings, 1 reply; 18+ messages in thread
From: PFC @ 2005-09-25 16:08 UTC (permalink / raw)
To: Joshua D. Drake <jd@commandprompt.com>; Dave Cramer <pg@fastcrypt.com>; +Cc: Michael Ben-Nes <miki@canaan.co.il>; pgsql-performance
> The common explanation is that CPUs are so fast now that it doesn't make
> a difference.
> From my experience software raid works very, very well. However I have
> never put
> software raid on anything that is very heavily loaded.
Even for RAID5 ? it uses a bit more CPU for the parity calculations.
An advantage of software raid, is that if the RAID card dies, you have to
buy the same one ; whether I think that you can transfer a bunch of
software RAID5 disks to another machine if the machine they're in dies...
^ permalink raw reply [nested|flat] 18+ messages in thread
* Re: Advice on RAID card
@ 2005-09-25 16:22 Joshua D. Drake <jd@commandprompt.com>
parent: PFC <lists@boutiquenumerique.com>
0 siblings, 2 replies; 18+ messages in thread
From: Joshua D. Drake @ 2005-09-25 16:22 UTC (permalink / raw)
To: PFC <lists@boutiquenumerique.com>; +Cc: Dave Cramer <pg@fastcrypt.com>; Michael Ben-Nes <miki@canaan.co.il>; pgsql-performance
>
> Even for RAID5 ? it uses a bit more CPU for the parity calculations.
I honestly can't speak to RAID 5. I don't (and won't) use it. RAID 5 is
a little brutal when under
heavy write load. I use either 1, or 10.
> An advantage of software raid, is that if the RAID card dies, you
> have to buy the same one ; whether I think that you can transfer a
> bunch of software RAID5 disks to another machine if the machine
> they're in dies...
There is a huge advantage to software raid on all kinds of levels. If
you have the CPU then I suggest
it. However you will never get the performance out of software raid on
the high level (think 1 gig of cache)
that you would on a software raid setup.
It is a bit of a tradeoff but for most installations software raid is
more than adequate.
Sincerely,
Joshua D. Drake
--
Your PostgreSQL solutions company - Command Prompt, Inc. 1.800.492.2240
PostgreSQL Replication, Consulting, Custom Programming, 24x7 support
Managed Services, Shared and Dedicated Hosting
Co-Authors: plPHP, plPerlNG - http://www.commandprompt.com/
^ permalink raw reply [nested|flat] 18+ messages in thread
* Re: Advice on RAID card
@ 2005-09-25 16:53 PFC <lists@boutiquenumerique.com>
parent: Joshua D. Drake <jd@commandprompt.com>
1 sibling, 2 replies; 18+ messages in thread
From: PFC @ 2005-09-25 16:53 UTC (permalink / raw)
To: Joshua D. Drake <jd@commandprompt.com>; +Cc: Dave Cramer <pg@fastcrypt.com>; Michael Ben-Nes <miki@canaan.co.il>; pgsql-performance
> There is a huge advantage to software raid on all kinds of levels. If
> you have the CPU then I suggest
> it. However you will never get the performance out of software raid on
> the high level (think 1 gig of cache)
> that you would on a software raid setup.
>
> It is a bit of a tradeoff but for most installations software raid is
> more than adequate.
Which makes me think that I will use Software Raid 5 and convert the
price of the card into RAM.
This should be nice for a budget server.
Gonna investigate now if Linux software RAID5 is rugged enough. Can
always buy the a card later if not.
Thanks all for the advice, you were really helpful.
^ permalink raw reply [nested|flat] 18+ messages in thread
* Re: Advice on RAID card
@ 2005-09-25 17:41 Greg Stark <gsstark@mit.edu>
parent: PFC <lists@boutiquenumerique.com>
1 sibling, 1 reply; 18+ messages in thread
From: Greg Stark @ 2005-09-25 17:41 UTC (permalink / raw)
To: PFC <lists@boutiquenumerique.com>; +Cc: Joshua D. Drake <jd@commandprompt.com>; Dave Cramer <pg@fastcrypt.com>; Michael Ben-Nes <miki@canaan.co.il>; pgsql-performance
PFC <lists@boutiquenumerique.com> writes:
> Which makes me think that I will use Software Raid 5 and convert the
> price of the card into RAM.
> This should be nice for a budget server.
> Gonna investigate now if Linux software RAID5 is rugged enough. Can
> always buy the a card later if not.
Raid 5 is perhaps the exception here. For Raid 5 a substantial amount of CPU
power is needed.
Also, Raid 5 is particularly inappropriate for write-heavy Database traffic.
Raid 5 actually hurts write latency dramatically and Databases are very
sensitive to latency.
On the other hand if your database is primarily read-only then Raid 5 may not
be a problem and may be faster than raid 1+0.
--
greg
^ permalink raw reply [nested|flat] 18+ messages in thread
* Re: Advice on RAID card
@ 2005-09-25 18:09 Luke Lonergan <LLonergan@greenplum.com>
0 siblings, 0 replies; 18+ messages in thread
From: Luke Lonergan @ 2005-09-25 18:09 UTC (permalink / raw)
To: Joshua D. Drake <jd@commandprompt.com>; PFC <lists@boutiquenumerique.com>; +Cc: Dave Cramer <pg@fastcrypt.com>; Michael Ben-Nes <miki@canaan.co.il>; pgsql-performance
>> Even for RAID5 ? it uses a bit more CPU for the parity calculations.
> I honestly can't speak to RAID 5. I don't (and won't) use it. RAID 5 is
> a little brutal when under
> heavy write load. I use either 1, or 10.
Yes, for RAID5 software RAID is better than HW RAID today - the modern general purpose CPUs are *much* faster at the ECC calculations than the CPUs on most modern hardware SCSI RAID cards.
Note that there is a trend toward SATA RAID, and the newer crop of SATA RAID adapters from companies like 3Ware are starting to be much faster than software RAID with lower CPU consumption.
Use non-RAID SCSI controllers if you want high performance and low CPU consumption with software RAID. The write-combining and TCQ of SCSI is well suited to SW RAID. Note that if you use HW RAID controllers for SW RAID, expect slightly better performance than in their HW RAID mode, but much higher CPU consumption, as they make for terrible JBOD SCSI controllers. This is especially true of the HP smartarray controllers with their Linux drivers.
- Luke
Greenplum
^ permalink raw reply [nested|flat] 18+ messages in thread
* Re: Advice on RAID card
@ 2005-09-25 18:13 Michael Stone <mstone+postgres@mathom.us>
parent: Greg Stark <gsstark@mit.edu>
0 siblings, 0 replies; 18+ messages in thread
From: Michael Stone @ 2005-09-25 18:13 UTC (permalink / raw)
To: pgsql-performance
On Sun, Sep 25, 2005 at 01:41:06PM -0400, Greg Stark wrote:
>Also, Raid 5 is particularly inappropriate for write-heavy Database traffic.
>Raid 5 actually hurts write latency dramatically and Databases are very
>sensitive to latency.
Software raid 5 actually may have an advantage here. The main cause for
high raid5 write latency is the necessity of having blocks from each
disk available to calculate the parity. The chances of a pc with several
gigs of ram having all the blocks cached (thus not requiring any reads)
are higher than on a hardware raid with several hundred megs of ram.
Mike Stone
^ permalink raw reply [nested|flat] 18+ messages in thread
* Re: Advice on RAID card
@ 2005-09-25 20:54 Steinar H. Gunderson <sgunderson@bigfoot.com>
parent: PFC <lists@boutiquenumerique.com>
1 sibling, 0 replies; 18+ messages in thread
From: Steinar H. Gunderson @ 2005-09-25 20:54 UTC (permalink / raw)
To: pgsql-performance
On Sun, Sep 25, 2005 at 06:53:57PM +0200, PFC wrote:
> Gonna investigate now if Linux software RAID5 is rugged enough. Can
> always buy the a card later if not.
Note that 2.6.13 and 2.6.14 have several improvements to the software RAID
code, some with regard to ruggedness. You might want to read the changelogs.
/* Steinar */
--
Homepage: http://www.sesse.net/
^ permalink raw reply [nested|flat] 18+ messages in thread
* Re: Advice on RAID card
@ 2005-09-26 00:10 Chris Browne <cbbrowne@acm.org>
parent: Joshua D. Drake <jd@commandprompt.com>
1 sibling, 0 replies; 18+ messages in thread
From: Chris Browne @ 2005-09-26 00:10 UTC (permalink / raw)
To: pgsql-performance
jd@commandprompt.com ("Joshua D. Drake") writes:
> There is a huge advantage to software raid on all kinds of
> levels. If you have the CPU then I suggest it. However you will
> never get the performance out of software raid on the high level
> (think 1 gig of cache) that you would on a software raid setup.
This appears to be a case where the "ludicrous MHz increases" on
desktop CPUs has actually provided a material benefit.
The sorts of embedded controllers typically used on RAID controllers
are StrongARMs and i960s, and, well, 250MHz is actually fast for
these.
When AMD and Intel fight over adding gigahertz and megabytes of cache
to their chips, this means that the RAID work can get pushed over to
one's "main CPU" without chewing up terribly much of its bandwidth.
That says to me that in the absence of battery backed cache, it's not
worth having a "bottom-end" RAID controller. Particularly if the
death of the controller would be likely to kill your data.
Battery-backed cache changes the value proposition, of course...
--
select 'cbbrowne' || '@' || 'acm.org';
http://cbbrowne.com/info/linuxdistributions.html
All generalizations are false, including this one.
^ permalink raw reply [nested|flat] 18+ messages in thread
* Re: Advice on RAID card
@ 2005-09-26 11:01 Ron Peacetree <rjpeace@earthlink.net>
0 siblings, 1 reply; 18+ messages in thread
From: Ron Peacetree @ 2005-09-26 11:01 UTC (permalink / raw)
To: PFC <lists@boutiquenumerique.com>; pgsql-performance
While I understand being economical, at some point one crosses the line
to being penny wise and pound foolish.
How much is the data on this server going to be worth?
How much much will it cost you to recover or restore it (assuming that
is even possible if you lose it)?
If your data is worth nothing or the cost to recover or restore it is
negligible, then you don't need (nor should want) a DB server. You'll
get higher performance at less cost via a number of other methods.
OTOH, if you data _does_ have value by any of the above metrics,
then it is worth it to pay attention to reliable, safe, fast, physical IO.
Battery backed HD caches of appropriate size are usually well worth
the $, as they pay for themselves (and then some) with the first data
loss they prevent.
RAID 5 means you are _always_ only 2 HDs from data loss, and 1 HD
from a serious performance hit. Part of the trade-off with using SATA
HDs that cost 1/3-1/4 their U320 15Krpm brethren is that such
circumstances are +FAR+ more likely with SATA HDs.
If you are not going to use RAID 10 because of cost issues, then
spend the $ to get the biggest battery backed cache you can afford
and justify as being cheaper than what the proper RAID 6 or RAID 10
setup would cost you. Even if you are going to use SW RAID and the
controller will just be a JBOD controller.
On the general subject of costs...
At this writing, SODIMM RAM costs ~$100 (US) per GB. Standard
DIMMs cost ~$75 per GB unless you buy 4GB ones, in which case
they cost ~$100 per GB.
The "sweet spot" in SATA HD pricing is ~$160 for 320GB at 7200rpm
(don't buy the 36GB or 74GB WD Raptors, they are no longer worth
it). If you are careful you can get SATA HD's with 16MB rather than
8MB buffers for that price. Each such HD will give you ~50MB/s of
raw Average Sustained Transfer Rate.
Decent x86 compatible CPUs are available for ~$200-$400 apiece.
Rarely will a commodity HW DB server need a more high end CPU.
Some of the above numbers rate to either fall to 1/2 cost or 2x in value
for the dollar within the next 6-9 months, and all of them will within the
next 18 months. And so will RAID controller costs.
Your salary will hopefully not degrade at that rate, and it is unlikely that
your value for the dollar will increase at that rate. Nor is it likely that
data worth putting on a DB server will do so.
Figure out what your required performance and reliability for the next 18
months is going to be, and buy the stuff from the above list that will
sustain that. No matter what.
Anything less rates _highly_ to end up costing you and your organization
more money within the next 18months than you will "save" in initial
acquisition cost.
Ron
-----Original Message-----
From: PFC <lists@boutiquenumerique.com>
Sent: Sep 24, 2005 12:27 PM
Subject: Re: [PERFORM] Advice on RAID card
> It looks like a rebranded low end Adaptec 64MB PCI-X <-> SATA RAID card.
> Looks like the 64MB buffer is not upgradable.
> Looks like it's SATA, not SATA II
Yeah, that's exactly what it is. I can get one for 150 Euro, the Areca is
at least 600. This is for a budget server so while it would be nice to
have all the high-tech stuff, it's not the point. My question was raher,
is it one of the crap RAID5 cards which are actually SLOWER than plain IDE
disks, or is it decent, even though low-end (and cheap), and worth it
compared to software RAID5 ?
> Assuming you are not building 1U boxes, get one of the full height
> cards and order it with the maximum size buffer you can afford.
> The cards take 1 SODIMM, so that will be a max of 1GB or 2GB
> depending on whether 2GB SODIMMs are available to you yet.
It's for a budget dev server which should have RAID5 for reliability, but
not necessarily stellar performance (and price). I asked about this card
because I can get one at a good price.
Thanks for taking the time to answer.
^ permalink raw reply [nested|flat] 18+ messages in thread
* Re: Advice on RAID card
@ 2005-09-29 14:25 Michael Ben-Nes <miki@canaan.co.il>
parent: Ron Peacetree <rjpeace@earthlink.net>
0 siblings, 0 replies; 18+ messages in thread
From: Michael Ben-Nes @ 2005-09-29 14:25 UTC (permalink / raw)
To: Ron Peacetree <rjpeace@earthlink.net>; +Cc: PFC <lists@boutiquenumerique.com>; pgsql-performance
I think the answer is simple
if the question is low end Raid card or software ? go on the software
and youll get better performance.
If this is a high end server i wouldnt think twice. HW RAID is a must
and not only because the performance but because the easynes ( hot swap
and such ) and the battery
Ron Peacetree wrote:
>While I understand being economical, at some point one crosses the line
>to being penny wise and pound foolish.
>
>How much is the data on this server going to be worth?
>How much much will it cost you to recover or restore it (assuming that
>is even possible if you lose it)?
>
>If your data is worth nothing or the cost to recover or restore it is
>negligible, then you don't need (nor should want) a DB server. You'll
>get higher performance at less cost via a number of other methods.
>
>OTOH, if you data _does_ have value by any of the above metrics,
>then it is worth it to pay attention to reliable, safe, fast, physical IO.
>
>Battery backed HD caches of appropriate size are usually well worth
>the $, as they pay for themselves (and then some) with the first data
>loss they prevent.
>
>RAID 5 means you are _always_ only 2 HDs from data loss, and 1 HD
>from a serious performance hit. Part of the trade-off with using SATA
>HDs that cost 1/3-1/4 their U320 15Krpm brethren is that such
>circumstances are +FAR+ more likely with SATA HDs.
>
>If you are not going to use RAID 10 because of cost issues, then
>spend the $ to get the biggest battery backed cache you can afford
>and justify as being cheaper than what the proper RAID 6 or RAID 10
>setup would cost you. Even if you are going to use SW RAID and the
>controller will just be a JBOD controller.
>
>On the general subject of costs...
>
>At this writing, SODIMM RAM costs ~$100 (US) per GB. Standard
>DIMMs cost ~$75 per GB unless you buy 4GB ones, in which case
>they cost ~$100 per GB.
>
>The "sweet spot" in SATA HD pricing is ~$160 for 320GB at 7200rpm
>(don't buy the 36GB or 74GB WD Raptors, they are no longer worth
>it). If you are careful you can get SATA HD's with 16MB rather than
>8MB buffers for that price. Each such HD will give you ~50MB/s of
>raw Average Sustained Transfer Rate.
>
>Decent x86 compatible CPUs are available for ~$200-$400 apiece.
>Rarely will a commodity HW DB server need a more high end CPU.
>
>Some of the above numbers rate to either fall to 1/2 cost or 2x in value
>for the dollar within the next 6-9 months, and all of them will within the
>next 18 months. And so will RAID controller costs.
>
>Your salary will hopefully not degrade at that rate, and it is unlikely that
>your value for the dollar will increase at that rate. Nor is it likely that
>data worth putting on a DB server will do so.
>
>Figure out what your required performance and reliability for the next 18
>months is going to be, and buy the stuff from the above list that will
>sustain that. No matter what.
>
>Anything less rates _highly_ to end up costing you and your organization
>more money within the next 18months than you will "save" in initial
>acquisition cost.
>
>Ron
>
>
>
>
>
>-----Original Message-----
>From: PFC <lists@boutiquenumerique.com>
>Sent: Sep 24, 2005 12:27 PM
>Subject: Re: [PERFORM] Advice on RAID card
>
>
>
>
>>It looks like a rebranded low end Adaptec 64MB PCI-X <-> SATA RAID card.
>>Looks like the 64MB buffer is not upgradable.
>>Looks like it's SATA, not SATA II
>>
>>
>
> Yeah, that's exactly what it is. I can get one for 150 Euro, the Areca is
>at least 600. This is for a budget server so while it would be nice to
>have all the high-tech stuff, it's not the point. My question was raher,
>is it one of the crap RAID5 cards which are actually SLOWER than plain IDE
>disks, or is it decent, even though low-end (and cheap), and worth it
>compared to software RAID5 ?
>
>
>
>>Assuming you are not building 1U boxes, get one of the full height
>>cards and order it with the maximum size buffer you can afford.
>>The cards take 1 SODIMM, so that will be a max of 1GB or 2GB
>>depending on whether 2GB SODIMMs are available to you yet.
>>
>>
>
> It's for a budget dev server which should have RAID5 for reliability, but
>not necessarily stellar performance (and price). I asked about this card
>because I can get one at a good price.
>
> Thanks for taking the time to answer.
>
>
>---------------------------(end of broadcast)---------------------------
>TIP 4: Have you searched our list archives?
>
> http://archives.postgresql.org
>
>
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^ permalink raw reply [nested|flat] 18+ messages in thread
end of thread, other threads:[~2005-09-29 14:25 UTC | newest]
Thread overview: 18+ messages (download: mbox mbox.gz follow: Atom feed)
-- links below jump to the message on this page --
2005-09-24 08:34 Advice on RAID card PFC <lists@boutiquenumerique.com>
2005-09-25 10:17 ` Michael Ben-Nes <miki@canaan.co.il>
2005-09-25 14:57 ` Dave Cramer <pg@fastcrypt.com>
2005-09-25 15:27 ` Mike Rylander <mrylander@gmail.com>
2005-09-25 15:42 ` Joshua D. Drake <jd@commandprompt.com>
2005-09-25 16:08 ` PFC <lists@boutiquenumerique.com>
2005-09-25 16:22 ` Joshua D. Drake <jd@commandprompt.com>
2005-09-25 16:53 ` PFC <lists@boutiquenumerique.com>
2005-09-25 17:41 ` Greg Stark <gsstark@mit.edu>
2005-09-25 18:13 ` Michael Stone <mstone+postgres@mathom.us>
2005-09-25 20:54 ` Steinar H. Gunderson <sgunderson@bigfoot.com>
2005-09-26 00:10 ` Chris Browne <cbbrowne@acm.org>
2005-09-25 15:59 ` Michael Stone <mstone+postgres@mathom.us>
2005-09-24 15:55 Re: Advice on RAID card Ron Peacetree <rjpeace@earthlink.net>
2005-09-24 16:27 ` PFC <lists@boutiquenumerique.com>
2005-09-25 18:09 Re: Advice on RAID card Luke Lonergan <LLonergan@greenplum.com>
2005-09-26 11:01 Re: Advice on RAID card Ron Peacetree <rjpeace@earthlink.net>
2005-09-29 14:25 ` Michael Ben-Nes <miki@canaan.co.il>
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