Re: What's the best hardver for PostgreSQL 8.1?

Have you done any benchmarking of the 9550SX against a software raid
configuration?

Luke Lonergan wrote:

>Frank,
>
>
>
>> You definitely DO NOT want to do RAID 5 on a database server. That
>> is probably the worst setup you could have, I've seen it have lower
>> performance than just a single hard disk.
>>
>>
>
>I've seen that on RAID0 and RAID10 as well.
>
>This is more about the quality and modernity of the RAID controller than
>anything else at this point, although there are some theoretical
>advantages of RAID10 from a random seek standpoint even if the adapter
>CPU is infinitely fast at checksumming. We're using RAID5 in practice
>for OLAP / Data Warehousing systems very successfully using the newest
>RAID cards from 3Ware (9550SX).
>
>Note that host-based SCSI raid cards from LSI, Adaptec, Intel, Dell, HP
>and others have proven to have worse performance than a single disk
>drive in many cases, whether for RAID0 or RAID5. In most circumstances
>I've seen, people don't even notice until they write a message to a
>mailing list about "my query runs slowly on xxx dbms". In many cases,
>after they run a simple sequential transfer rate test using dd, they see
>that their RAID controller is the culprit.
>
>Recently, I helped a company named DeepData to improve their dbms
>performance, which was a combination of moving them to software RAID50
>on Linux and getting them onto Bizgres. The disk subsystem sped up on
>the same hardware (minus the HW RAID card) by over a factor of 10. The
>downside is that SW RAID is a pain in the neck for management - you have
>to shut down the Linux host when a disk fails to replace it.
>
>- Luke
>
>
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--
*Benjamin Arai*
barai(at)cs(dot)ucr(dot)edu <emailto:barai(at)cs(dot)ucr(dot)edu>
http://www.benjaminarai.com