Re: Some pgbench results

I played a bit with kernnel versions as I was getting a kernel panic
on my Adaptec card. I downgraded to 2.6.11 (the original that came
with fedora core 4) and the panic went away, but more than that, the
performance on XFS went considerably higher. With the exact same
settings as before, I got now Average of 813.65tps with a standard
deviation of: 130.33.

I hope this kernel doesn't panic on me. But I'll know just tomorrow as
I'm pounding on the machine now.

Bye,

Guy.


On 3/23/06, Magnus Naeslund(f) <mag@fbab.net> wrote:
> Just Someone wrote:
> >
> > Initialized the data with: pgbench -i -s 100
> > Test runs: pgbench -s 100 -t 10000 -c 20
> > I did 20 runs, removed the first 3 runs from each sample to account
> > for stabilization.
>
> Did you re-initialize the test pgbench database between runs?
> I get weird results otherwise since some integers gets overflowed in the
> test (it doesn't complete the full 10000 transactions after the first run).
>
> > Here are the results in tps without connection
> > establishing:
> >
> > FS:       JFS     XFS     EXT3
> > Avg:     462      425       319
> > Stdev:  104        74       106
> >
>
> Could you please tell me what stripe size you have on the raid system?
> Could you also share the mkfs and mount options on each filesystem you
> tried?
>
> I ran some tests on an somewhat similar system:
> A supermicro H8SSL-i-B motherboard with one dual core opteron 165 with
> 4gb of memory, debian sarge amd64 (current stable) but with a pristine
> kernel.org 2.6.16 kernel (there's no debian patches or packages yet).
>
> It has a 3ware 9550 + BBU sata raid card with 6 disks in a raid 10
> configuration with 256kb stripe size. I think this results in about
> 200mb/s raw read performance and about 155mb/s raw write performance (as
> in tested with dd:ing a 10gb file back and forth).
> I had no separate WAL device/partition, only tweaked postgresql.conf.
>
> I get about 520-530 tps with your pgbench parameters on ext3 but very
> poor (order of magnitude) performance on xfs (that's why I ask of your
> mkfs parameters).
>
> A hint on using a raided ext3 system is to use whole block device
> instead of partitions to align the data better and use data=journal with
> a big journal. This might seem counter-productive at first (it did to
> me) but I increased my throughput a lot when using this.
>
> My filesystem parameters are calculated like this:
> stripe=256 # <- 256k raid stripe size
> bsize=4 # 4k blocksize
> bsizeb=$(( $bsize * 1024 )) # in bytes
> stride=$(( $stripe / $bsize ))
>
> mke2fs -b $bsizeb -j -J size=400 -m 1 -O sparse_super \
>   -T largefile4 -E stride=$stride /dev/sdb
>
> Mounted with: mount -t ext3 -o data=journal,noatime /dev/sdb /mnt/test8
>
> I'm a little surprised that I can get more pgbench performance out of my
> system since you're using 10K scsi disks. Please try the above settings
> and see if it helps you...
>
> I've not run so many tests yet, I'll do some more after the weekend...
>
> Regards,
> Magnus
>
>
>


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