Re: Performance increase with elevator=deadline

Hi,

Il giorno 11/apr/08, alle ore 20:03, Craig Ringer ha scritto:
>
> Speaking of I/O performance with PostgreSQL, has anybody here done
> any testing to compare results with LVM to results with the same
> filesystem on a conventionally partitioned or raw volume? I'd
> probably use LVM even at a performance cost because of its admin
> benefits, but I'd be curious if there is any known cost for use with
> Pg. I've never been able to measure one with other workloads.

I performed some tests some time ago. LVM is significantly slower.
The disk subsystem is a HP P400/512MB battery-backed controller with 4
disks in raid 10.
See the tests:


ext3 tests:

bonnie++ -s 16000 -u 0 -f -b
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========================================================================

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
              16000M           153637  50 78895  17           204124
17 700.6   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  2233  10 +++++ +++  2606   8  2255  10 +++++ ++
+  2584   7
16000M,,,153637,50,78895,17,,,204124,17,700.6,1,16,2233,10,+++++,+++,
2606,8,2255,10,+++++,+++,2584,7


bonnie++ -s 16000 -u 0 -f
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========================================================================

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
              16000M           162223  51 77277  17           207055
17 765.3   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 +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++
+++++ +++
16000M,,,162223,51,77277,17,,,207055,17,765.3,1,16,+++++,+++,+++++,+++,
+++++,+++,+++++,+++,+++++,+++,+++++,+++

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========================================================================

LVM tests:

bonnie++ -u 0 -f -s 16000 -b
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
              16000M           153768  52 53420  13           177414
15 699.8   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  2158   9 +++++ +++  2490   7  2177   9 +++++ ++
+  2460   7
16000M,,,153768,52,53420,13,,,177414,15,699.8,1,16,2158,9,+++++,+++,
2490,7,2177,9,+++++,+++,2460,7

bonnie++ -u 0 -f -s 16000
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
              16000M           161476  53 54904  13           171693
14 774.3   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 +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++
+++++ +++
16000M,,,161476,53,54904,13,,,171693,14,774.3,1,16,+++++,+++,+++++,+++,
+++++,+++,+++++,+++,+++++,+++,+++++,+++

Bye,
e.