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.