Re: Two identical systems, radically different performance

[Evgeny Shishkin <itparanoia@xxxxxxxxx>]

On Oct 9, 2012, at 2:06 AM, Craig James <cjames@xxxxxxxxxxxxxx> wrote:

On Mon, Oct 8, 2012 at 2:57 PM, Evgeny Shishkin <itparanoia@xxxxxxxxx> wrote:

On Oct 9, 2012, at 1:45 AM, Craig James <cjames@xxxxxxxxxxxxxx> wrote:

I tested both the RAID10 data disk and the RAID1 xlog disk with bonnie++.  The xlog disks were almost identical in performance.  The RAID10 pg-data disks looked like this:

Old server:
Version  1.96       ------Sequential Output------ --Sequential Input- --Random-
Concurrency   1     -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
xenon        24064M   687  99 203098  26 81904  16  3889  96 403747  31 737.6  31
Latency             20512us     469ms     394ms   21402us     396ms     112ms
Version  1.96       ------Sequential Create------ --------Random Create--------
xenon               -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
                 16 15953  27 +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++
Latency             43291us     857us     519us    1588us      37us     178us
1.96,1.96,xenon,1,1349726125,24064M,,687,99,203098,26,81904,16,3889,96,403747,31,737.6,31,16,,,,,15953,27,+++++,+++,+++++,++\
+,+++++,+++,+++++,+++,+++++,+++,20512us,469ms,394ms,21402us,396ms,112ms,43291us,857us,519us,1588us,37us,178us


New server:
Version  1.96       ------Sequential Output------ --Sequential Input- --Random-
Concurrency   1     -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
zinc         24064M   862  99 212143  54 96008  14  4921  99 279239  17 752.0  23
Latency             15613us     598ms     597ms    2764us     398ms     215ms
Version  1.96       ------Sequential Create------ --------Random Create--------
zinc                -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
                 16 20380  26 +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++
Latency               487us     627us     407us     972us      29us     262us
1.96,1.96,zinc,1,1349722017,24064M,,862,99,212143,54,96008,14,4921,99,279239,17,752.0,23,16,,,,,20380,26,+++++,+++,+++++,+++\
,+++++,+++,+++++,+++,+++++,+++,15613us,598ms,597ms,2764us,398ms,215ms,487us,627us,407us,972us,29us,262us

Sequential Input on the new one is 279MB/s, on the old 400MB/s. 

But why? What have I overlooked?

blockdev --setra 32000 ?

Also you benchmarked volume for pgdata? Can you provide benchmarks for wal volume?

Thanks,
Craig