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
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
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