Thread: Re: 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 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
> 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.
>> 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 ECCcalculations 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 startingto 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-combiningand TCQ of SCSI is well suited to SW RAID. Note that if you use HW RAID controllers for SW RAID, expect slightlybetter performance than in their HW RAID mode, but much higher CPU consumption, as they make for terrible JBOD SCSIcontrollers. This is especially true of the HP smartarray controllers with their Linux drivers. - Luke Greenplum
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.
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 > > -- -------------------------- 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 --------------------------