Re: Filesystem benchmarking for pg 8.3.3 server - Mailing list pgsql-performance

From Henrik
Subject Re: Filesystem benchmarking for pg 8.3.3 server
Date
Msg-id 90A23365-4FD6-414F-8F73-F5BC7BE4AC07@mac.se
Whole thread Raw
In response to Re: Filesystem benchmarking for pg 8.3.3 server  ("Mark Wong" <markwkm@gmail.com>)
List pgsql-performance
8 aug 2008 kl. 18.44 skrev Mark Wong:

> On Fri, Aug 8, 2008 at 8:08 AM, Henrik <henke@mac.se> wrote:
>> But random writes should be faster on a RAID10 as it doesn't need to
>> calculate parity. That is why people suggest RAID 10 for datases,
>> correct?
>> I can understand that RAID5 can be faster with sequential writes.
>
> There is some data here that does not support that RAID5 can be faster
> than RAID10 for sequential writes:
>
> http://wiki.postgresql.org/wiki/HP_ProLiant_DL380_G5_Tuning_Guide
I'm amazed by the big difference on hardware vs software raid.

I set up e new Dell(!) system against a MD1000 DAS with singel quad
core 2,33 Ghz, 16GB RAM and Perc/6E raid controllers with 512MB BBU.

I set up a RAID 10 on 4 15K SAS disks.

I ran IOZone against this partition with ext2 filesystem and got the
following results.

safeuser@safecube04:/$ iozone -e -i0 -i1 -i2 -i8 -t1 -s 1000m -r 8k -
+u -F /database/iotest
    Iozone: Performance Test of File I/O
            Version $Revision: 3.279 $
        Compiled for 64 bit mode.
        Build: linux

    Children see throughput for  1 initial writers     =  254561.23 KB/sec
    Parent sees throughput for  1 initial writers     =  253935.07 KB/sec
    Min throughput per process             =  254561.23 KB/sec
    Max throughput per process             =  254561.23 KB/sec
    Avg throughput per process             =  254561.23 KB/sec
    Min xfer                     = 1024000.00 KB
    CPU Utilization: Wall time    4.023    CPU time    0.740    CPU
utilization  18.40 %


    Children see throughput for  1 rewriters     =  259640.61 KB/sec
    Parent sees throughput for  1 rewriters     =  259351.20 KB/sec
    Min throughput per process             =  259640.61 KB/sec
    Max throughput per process             =  259640.61 KB/sec
    Avg throughput per process             =  259640.61 KB/sec
    Min xfer                     = 1024000.00 KB
    CPU utilization: Wall time    3.944    CPU time    0.460    CPU
utilization  11.66 %


    Children see throughput for  1 readers         = 2931030.50 KB/sec
    Parent sees throughput for  1 readers         = 2877172.20 KB/sec
    Min throughput per process             = 2931030.50 KB/sec
    Max throughput per process             = 2931030.50 KB/sec
    Avg throughput per process             = 2931030.50 KB/sec
    Min xfer                     = 1024000.00 KB
    CPU utilization: Wall time    0.349    CPU time    0.340    CPU
utilization  97.32 %


    Children see throughput for 1 random readers     = 2534182.50 KB/sec
    Parent sees throughput for 1 random readers     = 2465408.13 KB/sec
    Min throughput per process             = 2534182.50 KB/sec
    Max throughput per process             = 2534182.50 KB/sec
    Avg throughput per process             = 2534182.50 KB/sec
    Min xfer                     = 1024000.00 KB
    CPU utilization: Wall time    0.404    CPU time    0.400    CPU
utilization  98.99 %

    Children see throughput for 1 random writers     =   68816.25 KB/sec
    Parent sees throughput for 1 random writers     =   68767.90 KB/sec
    Min throughput per process             =   68816.25 KB/sec
    Max throughput per process             =   68816.25 KB/sec
    Avg throughput per process             =   68816.25 KB/sec
    Min xfer                     = 1024000.00 KB
    CPU utilization: Wall time   14.880    CPU time    0.520    CPU
utilization   3.49 %


So compared to the HP 8000 benchmarks this setup is even better than
the software raid.

But I'm skeptical of iozones results as when I run the same test
agains 6 standard SATA drives in RAID5 I got random writes of 170MB /
sek (!). Sure 2 more spindles but still.

Cheers,
Henke


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