Thread: Réf. : Re: NAS, SAN or any alternatesolution ?
Thanks a lot Scott.
It seems that we were totally wrong when considering a network storage solution. I've read your techdoc http://techdocs.postgresql.org/guides/DiskTuningGuide and found many interesting remarks.
I think that we will know focus on external Raid systems which seem to be relativily affordable compared to NAS or SAN (we would have had the budget for one of these).
As we don't plan to have more than 5 connections (I.E process), we think SATA drives would fit our requirements. Could this be an issue for an after crash recovery ?
We also hesitate concerning the raid level to use. We are currently comparing raid 1+0 and raid 5 but we have no actual idea on which one to use.
Our priorities are :
1) performance
2) recovery
3) price
4) back-up
It could be nice to have any comments from people who have already set up a similar platform, giving some precise details of the hardware configuration :
- brand of the raid device,
- technology used (SCSI/IDE, RAID level ...),
- size of the database, number of disks/size of disks ...
Such a knowledge base may be useful to convince people to migrate to opensource cheap reliable solutions.
Thanks again.
Benjamin.
| "Scott Marlowe" <smarlowe@qwest.net> Envoyé par : pgsql-performance-owner@postgresql.org 20/07/2004 10:20 | Pour : bsimon@loxane.com cc : pgsql-performance@postgresql.org Objet : Re: [PERFORM] NAS, SAN or any alternate solution ? |
On Tue, 2004-07-20 at 01:52, bsimon@loxane.com wrote:
> Hi all,
>
> I've been searching the list for a while but couldn't find any
> up-to-date information relating to my problem.
> We have a production server with postgresql on cygwin that currently
> deels with about 200 Gigs of data (1 big IDE drive). We plan to move
> to linux for some reasons I don't have to explain.
> Our aim is also to be able to increase our storage capacity up to
> approximately 1 or 2 terabytes and to speed up our production process.
> As we are a small "microsoft addicted" company , we have some
> difficulties to choose the best configuration that would best meet our
> needs.
> Our production process is based on transaction (mostly huge inserts)
> and disk access is the main bottlle-neck.
>
> Our main concern is hardware related :
>
> Would NAS or SAN be good solutions ? (I've read that NAS uses NFS
> which could slow down the transfer rate ??)
> Has anyone ever tried one of these with postgresql ?
Your best bet would likely be a large external RAID system with lots o
cache. Next would be a fast internal RAID card like the LSI Megaraid
cards, with lots of drives and batter backed cache. Next would be a
SAN, but be careful, there may be issues with some cards and their
drivers under linux, research them well before deciding. NFS is right
out if you want good performance AND reliability.
The cheapest solution that is likely to meet your needs would be the
internal RAID card with battery backed cache.
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bsimon@loxane.com wrote: > > As we don't plan to have more than 5 connections (I.E process), we > think SATA drives would fit our requirements. Could this be an issue > for an after crash recovery ? > If you can disable the write ATA write cache, then you have safety. Unfortunately many cards under Linux show up as SCSI devices, and you can't access this setting. Does anyone know if the newer SATA cards let you control this? You might want to keep and eye on the upcoming native windows port in 7.5 - It will come with a fearsome array of caveats... but you have been running cygwin in production! - and I am inclined to think the native port will be more solid than this configuration. regards Mark
On Tue, 2004-07-20 at 03:32, bsimon@loxane.com wrote: > Thanks a lot Scott. > > It seems that we were totally wrong when considering a network storage > solution. I've read your techdoc > http://techdocs.postgresql.org/guides/DiskTuningGuide and found many > interesting remarks. > I think that we will know focus on external Raid systems which seem to > be relativily affordable compared to NAS or SAN (we would have had the > budget for one of these). > As we don't plan to have more than 5 connections (I.E process), we > think SATA drives would fit our requirements. Could this be an issue > for an after crash recovery ? If you're looking at (S)ATA RAID, definitely look at escalade, as another poster mentioned. Last year I and a few other folks on the lists were testing RAID controllers for survival of the power plug pull test, and the Escalade passed (someone else did the testing, I tested the LSI MegaRAID 320-2 controller with battery backed cache). > We also hesitate concerning the raid level to use. We are currently > comparing raid 1+0 and raid 5 but we have no actual idea on which one > to use. > > Our priorities are : > 1) performance > 2) recovery > 3) price > 4) back-up Basically, for a smaller number of drivers, RAID 1+0 is almost always a win over RAID 5. As the number of drives in the array grows, RAID 5 usually starts to pull back in the lead. RAID 5 definitely gives you the most storage for your dollar of any of the redundant array types. The more important point of a RAID controller is that it have battery backed cache to make sure that the database server isn't waiting for WAL writes all the time. A single port LSI Megaraid 320-1 controller is only about $500 or less, the last time I checked (with battery backed cache, order it WITH the battery and cache, otherwise you may have a hard time finding the right parts later on.) It supports hot spares for automatic rebuild.