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Re: RAID stripe size question

From: "Mikael Carneholm" <Mikael(dot)Carneholm(at)WirelessCar(dot)com>
To: "Markus Schaber" <schabi(at)logix-tt(dot)com>
Cc: <pgsql-performance(at)postgresql(dot)org>
Subject: Re: RAID stripe size question
Date: 2006-07-17 12:52:28
Message-ID: 7F10D26ECFA1FB458B89C5B4B0D72C2B4E4BDF@sesrv12.wirelesscar.com (view raw or flat)
Thread:
Lists: pgsql-performance
>> This is something I'd also would like to test, as a common 
>> best-practice these days is to go for a SAME (stripe all, mirror
everything) setup.
>> From a development perspective it's easier to use SAME as the 
>> developers won't have to think about physical location for new 
>> tables/indices, so if there's no performance penalty with SAME I'll 
>> gladly keep it that way.

>Usually, it's not the developers task to care about that, but the DBAs
responsibility.

As we don't have a full-time dedicated DBA (although I'm the one who do
most DBA related tasks) I would aim for making physical location as
transparent as possible, otherwise I'm afraid I won't be doing anything
else than supporting developers with that - and I *do* have other things
to do as well :)

>> In a previous test, using cd=5000 and cs=20 increased transaction 
>> throughput by ~20% so I'll definitely fiddle with that in the coming 
>> tests as well.

>How many parallel transactions do you have?

That was when running BenchmarkSQL
(http://sourceforge.net/projects/benchmarksql) with 100 concurrent users
("terminals"), which I assume means 100 parallel transactions at most.
The target application for this DB has 3-4 times as many concurrent
connections so it's possible that one would have to find other cs/cd
numbers better suited for that scenario. Tweaking bgwriter is another
task I'll look into as well..

Btw, here's the bonnie++ results from two different array sets (10+18,
4+24) on the MSA1500:

LUN: WAL, 10 disks, stripe size 32K
------------------------------------
Version  1.03       ------Sequential Output------ --Sequential Input-
--Random-
                    -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
sesell01        32G 56139  93 73250  22 16530   3 30488  45 57489   5
477.3   1
                    ------Sequential Create------ --------Random
Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read---
-Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
/sec %CP
                 16  2458  90 +++++ +++ +++++ +++  3121  99 +++++ +++
10469  98


LUN: WAL, 4 disks, stripe size 8K
----------------------------------
Version  1.03       ------Sequential Output------ --Sequential Input-
--Random-
                    -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
sesell01        32G 49170  82 60108  19 13325   2 15778  24 21489   2
266.4   0
                    ------Sequential Create------ --------Random
Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read---
-Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
/sec %CP
                 16  2432  86 +++++ +++ +++++ +++  3106  99 +++++ +++
10248  98


LUN: DATA, 18 disks, stripe size 32K
-------------------------------------
Version  1.03       ------Sequential Output------ --Sequential Input-
--Random-
                    -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
sesell01        32G 59990  97 87341  28 19158   4 30200  46 57556   6
495.4   1
                    ------Sequential Create------ --------Random
Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read---
-Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
/sec %CP
                 16  1640  92 +++++ +++ +++++ +++  1736  99 +++++ +++
10919  99


LUN: DATA, 24 disks, stripe size 64K
-------------------------------------
Version  1.03       ------Sequential Output------ --Sequential Input-
--Random-
                    -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
sesell01        32G 59443  97 118515  39 25023   5 30926  49 60835   6
531.8   1
                    ------Sequential Create------ --------Random
Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read---
-Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
/sec %CP
                 16  2499  90 +++++ +++ +++++ +++  2817  99 +++++ +++
10971 100

Regards,
Mikael

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Subject: Re: RAID stripe size question
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