On 01/28/2005-10:59AM, Alex Turner wrote:
> At this point I will interject a couple of benchmark numbers based on
> a new system we just configured as food for thought.
>
> System A (old system):
> Compaq Proliant Dual Pentium III 933 with Smart Array 5300, one RAID
> 1, one 3 Disk RAID 5 on 10k RPM drives, 2GB PC133 RAM. Original
> Price: $6500
>
> System B (new system):
> Self Built Dual Opteron 242 with 2x3ware 9500S-8MI SATA, one RAID 1
> (OS), one 4 drive RAID 10 (pg_xlog), one 6 drive RAID 10 (data) on 10k
> RPM Raptors, 4GB PC3200 RAM. Current price $7200
>
> System A for our large insert job: 125 minutes
> System B for our large insert job: 10 minutes.
>
> There is no logical way there should be a 12x performance difference
> between these two systems, maybe 2x or even 4x, but not 12x
>
Your system A has the absolute worst case Raid 5, 3 drives. The more
drives you add to Raid 5 the better it gets but it will never beat Raid
10. On top of it being the worst case, pg_xlog is not on a separate
spindle.
Your system B has a MUCH better config. Raid 10 is faster than Raid 5 to
begin with but on top of that you have more drives involved plus pg_xlog
is on a separate spindle.
I'd say I am not surprised by your performance difference.
> Bad controler cards/configuration will seriously ruin your day. 3ware
> escalade cards are very well supported on linux, and work excellently.
> Compaq smart array cards are not. Bonnie++ benchmarks show a 9MB/sec
> write, 29MB/sec read on the RAID 5, but a 172MB/sec write on the
> 6xRAID 10, and 66MB/sec write on the RAID 1 on the 3ware.
>
What does bonnie say about the Raid 1 on the Compaq? Comparing the two
Raid 1s is really the only valid comparison that can be made between
these two machines. Other than that you are comparing apples to
snow shovels.
