Re: [linux-lvm] Horrid performance with 2.4.{9,10,12} + LVM + ReiserFS

[Werner John <john@oswf.de>]

Jens Benecke writes:
> Hello,

Hello,

> this is CC'ed to LVM user list and ReiserFS because I don't know who to
> blame currently. ;)
> 
lets, see ...
> 
> I have severe performance problems with a 210G ReiserFS volume sitting on a
> LVM (1.0.1rc4) spread over three disks (Maxtor 60, 80, 80GB IDE). The
> system is a Duron 650MHz with via686b chipset and UDMA-100 capable IDE.
> /proc/cpuinfo, /proc/ide/via output see below. The hardware seems
> performant enough to me.
> [...]
> 
> ---------------------------------------------------------------------------
> hdparm output for the three disks:
> 
> server: /home# hdparm -tT /dev/hd[abcd]
> /dev/hda:
>  Timing buffer-cache reads:   128 MB in  0.86 seconds =148.84 MB/sec
>  Timing buffered disk reads:  64 MB in  2.12 seconds = 30.19 MB/sec
> /dev/hdc:
>  Timing buffer-cache reads:   128 MB in  0.84 seconds =152.38 MB/sec
>  Timing buffered disk reads:  64 MB in  2.28 seconds = 28.07 MB/sec
> /dev/hdd:
>  Timing buffer-cache reads:   128 MB in  0.86 seconds =148.84 MB/sec
>  Timing buffered disk reads:  64 MB in  2.36 seconds = 27.12 MB/sec

Well, you have 1 disk on a single channel (hda) and the other two as master
and slave on *one* channel. That's the bottleneck. If the disks are
accessed individually, you get the full performance (more or less). But if
*both* disks have to respond, performance drops horribly.

Best is to get a third IDE controller.

Yours,
	Werner

> 
> 
> bonnie++ output for the LVM volume: ---------------------------------------
> Version 1.01d       ------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
> server         256M  5596  97 24539  34  6926   7  5194  87 24662  17 115.1 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  7965  99 +++++ +++ 10546  99  5458  92 +++++ +++  8214 90
> server,256M,5596,97,24539,34,6926,7,5194,87,24662,17,115.1,1,16,7965,99,+++++,++
> ---------------------------------------------------------------------------
> 
> 
> 
> 
> -- 
> Jens Benecke ииииииии http://www.hitchhikers.de/ - Europas Mitfahrzentrale
> 
> Crypto regulations will only hinder criminals who obey the law.
> 
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