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[dm-devel] Re: DM performance issues



Sorry, I really should have given details on my system, especially the kernel version:

Linux 2.6.19-1.2911.fc6 #1 SMP x86_64

Pentium 4 3.00 GHz CPU, 1G RAM
ext3 on LVM on RAID-5 on 5 * 500G SATA drives.

Best,
-- Elliot

On Mar 7, 2007, at 19:36 , Elliot Lee wrote:

Hi all,

I've got a 1.8TB LVM-on-RAID filesystem that was performing OK but really didn't seem like it was going as fast as it should. I ran the commands below and got some pretty startling results...

A 60% performance hit for a linear mapping is heinous. What can I do to help get this fixed?

Best,
-- Elliot

# dmsetup create foo --table '0 3880910848 linear 9:0 0'

# dd if=/dev/md0 of=/dev/null bs=1048576 count=4096
4096+0 records in
4096+0 records out
4294967296 bytes (4.3 GB) copied, 20.2362 seconds, 212 MB/s

# dd if=/dev/mapper/foo of=/dev/null bs=1048576 count=4096
4096+0 records in
4096+0 records out
4294967296 bytes (4.3 GB) copied, 55.3597 seconds, 77.6 MB/s



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