Dell PowerEdge 2950 performance - Mailing list pgsql-performance

Hello,

I’ve recently been tasked with scalability/performance testing of a Dell PowerEdge 2950. This is the one with the new Intel Woodcrest Xeons. Since I haven’t seen any info on this box posted to the list, I figured people might be interested in the results, and maybe in return share a few tips on performance tweaks.

After doing some reading on the performance list, I realize that there’s a preference for Opteron; however, the goal of these experiments is to see what I can get the 2950 to do. I will also be comparing performance vs. a 1850 at some point, if there’s any interest I can post those numbers too.

Here’s the hardware:

2xDual Core 3.0 Ghz CPU (Xeon 5160- 1333Mhz FSB, 4 MB shared cache per socket)

8 GB RAM (DDR2, fully buffered, Dual Ranked, 667 Mhz)

6x300 10k RPM SAS drives

Perc 5i w/256 MB battery backed cache

The target application:

Mostly OLAP (large bulk loads, then lots of reporting, possibly moving to real-time loads in the future). All of this will be run on FreeBSD 6.1 amd64. (If I have some extra time, I might be able to run a few tests on linux just for comparison’s sake)

Test strategy:

Make sure the RAID is giving reasonable performance:

bonnie++ -d /u/bonnie -s 1000:8k

time bash -c "(dd if=/dev/zero of=bigfile count=125000 bs=8k && sync)"

Now, I realize that the above are overly simple, and not indicative of overall performance, however here’s what I’m seeing:

Single 10K 300 GB drive - ~75 Mb/s on both tests, more or less

RAID 10, 6 disks (3 sets of mirrored pairs) - ~117 Mb/s

The RAID 10 numbers look way off to me, so my next step is to go test some different RAID configs. I’m going to look at a mirrored pair, and a striped pair first, just to make sure the setup is sane. Then, RAID 5 x 6 disks, and mirrored pair + raid 10 with 4. Possibly software raid, however I’m not very familiar with this on FreeBSD.

Once I get the RAID giving me reasonable results (I would think that a raid 10 with 6 10k drives should be able to push >200 MB/s sustained IO…no?) I will move on to other more DB specific tests.

A few questions:

1) Does anyone have other suggestions for testing raw IO for the RAID?

2) What is reasonable IO (bonnie++, dd) for 4 or 6 disks- RAID 10?

3) For DB tests, I would like to compare performance on the different RAID configs and vs. the 1850. Maybe to assist also in some basic postgresql.conf and OS tuning (but that will be saved mostly for when I start application level testing). I realize that benchmarks don’t necessarily map to application performance, but it helps me establish a baseline for the hardware. I’m currently running pgbench, but would like something with a few more features (but hopefully without too much setup time). I’ve heard mention of the OSDL’s DBT tests, and I’m specifically interested in DBT-2 and DBT-3. Any suggestions here?

Here’s some initial numbers from pgbench (-s 50 –c 10 –t 100). Please keep in mind that these are default installs of FreeBSD 6.1 and Postgres 8.1.4- NO tuning yet.

1850: run1: 121 tps, run2: 132 tps, run3: 229 tps

2950: run1: 178 tps, run2: 201 tps, run3:259 tps

Obviously neither PG nor FreeBSD are taking advantage of all the hardware available in either case.

I will post the additional RAID numbers shortly…

Thanks,

Bucky