From: Herbert Poetzl <herbert@13thfloor.at>
To: linux-lvm@sistina.com
Subject: Re: [linux-lvm] LVM on Raid 5 Performance?
Date: Thu May 15 16:45:02 2003 [thread overview]
Message-ID: <20030515214531.GA22215@www.13thfloor.at> (raw)
In-Reply-To: <OFE2CD45B2.0EA112E9-ONC1256D27.002FA1CF-C1256D27.0030AED4@nl.ibm.com>
On Thu, May 15, 2003 at 10:51:44AM +0200, Rick van der Linde wrote:
>
>
> Hi All!
>
To cut it short LVM on 4 Disc RAID 5 reduces RAW
throughput about 45% from 33MB/s to 18MB/s :(
> >Has anybody any explanations why the LVM layer eats
> >up about 45% of the available throughput?
> >(in this configuration?)
>
> <SNIP results>
>
> I can't yet tell you why, I see same kind of results with
> RAID 5 on 4 IDE disks on seperate channels (as master).
> In my case I use an ATA133 and onboard ATA33 controller.
> In my case the RAID5 set performs about 50 MB/s and the LVM
> about 18 MB/s. I suspect my ATA controller as bottelneck
hmm, sounds interesting, especially because you
do not get ~ 27MB/s (55%) but 18MB/s the same as
I got ...
> because my disks which can do 40 MB/s om the ATA133
> controller suddenly operate at 18 MB/s on the ATA33.
> That made me decide to buy another ATA100/133 controller.
>
> As I searched internet on this issue I saw some discussion
> about ext3 in combo with md-raid and lvm. What filesystem
> did you use on your lvm volume on top of RAID5?
yeah, I read something similar, that was the reason
why I conducted my tests on the raw partitions
(without any filesystem on top ;)
> What's fun too is when I use ext3 on RAID5 I see a
> performance of about 48 MB/s.
> When I use reiserfs it reduces too abou 44 MB/s.
> ext2 shows almost the same results as ext3.
FYI: at least for ext2/ext3 you should make
sure that the 'stride' (raid options for mke2fs)
matches the block/stripe size of the underlying
RAID configuration ...
> Till now I same same results for ext2, ext3 and reiserfs
> in my case, however I still suspect my ATA33 channel
> to be the bottleneck in my case. When I have another
> ATA100/133 controller I'll post new results.
many thanks,
Herbert
>
> Rick
>
>
>
>
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@sistina.com
> http://lists.sistina.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
next prev parent reply other threads:[~2003-05-15 16:45 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-05-15 3:49 [linux-lvm] LVM on Raid 5 Performance? Rick van der Linde
2003-05-15 16:45 ` Herbert Poetzl [this message]
-- strict thread matches above, loose matches on Subject: below --
2003-05-15 9:51 Little, Chris
2003-05-14 9:07 Little, Chris
2003-05-15 3:01 ` Herbert Poetzl
2003-05-19 1:25 ` Jason H. Smith
2003-05-19 6:31 ` Herbert Poetzl
2003-05-24 19:11 ` Steven Lembark
2003-05-13 9:57 Little, Chris
2003-05-14 3:21 ` Herbert Poetzl
2003-05-13 8:36 Herbert Poetzl
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