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[linux-lvm] performance comparison soft-hardware RAID + LVM: bad



Hello,

I am interested in performance for hardware/software RAID
in combination with LVM

So I took a server (Dual Xeon 2.4GHz, 1Gb RAM), a RAID adapter,
some identical SCSI disks and configured it with several of these
options (using RH 8.0) and ran a few bonnie++ benchmarks.

Results are below. Anyone care to comment? Especially LVM performance
disappointed here.

LVM machine setup:

2 18Gb disks. I created 3 partitions on both disks, 128Mb, 512Mb and 17Gb
Equal partitions were combined into RAID-1 devices (md driver).
First md device mounted on /boot, second for swapfile, and third
as basis for LVM

Out of the volume group four LV were created and mounted as follows:

[root nbs-126 root]# df
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/vg0/root          4225092   1293064   2717400  33% /
/dev/md0                124323     11517    106387  10% /boot
/dev/vg0/home          4225092     32828   3977636   1% /home
none                    514996         0    514996   0% /dev/shm
/dev/vg0/var           4225092     51720   3958744   2% /var
/dev/vg0/mysql        16513960     32828  15642272   1% /var/lib/mysql

Is there a reason for the performance degradation I saw with LVM?

Regards,
Ron Arts


Version 1.02c ------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 nbs-126.offic 2008M 24005 99 66015 49 16148 7 27430 98 86915 15 369.0 1 single disk nbs-126.offic 2G 23422 99 70919 58 23800 11 25289 86 101485 17 433.4 1 s/w RAID-1 nbs-126.offic 2G 8152 99 49897 94 23092 27 9122 92 78056 38 331.1 2 s/w RAID-1 + LVM nbs-126.offic 4032M 19695 99 44056 42 14179 9 21526 94 86450 16 344.3 1 h/w RAID-1 nbs-126.offic 4032M 19916 99 24033 22 13343 9 22794 99 111662 30 388.5 1 h/w RAID-5 ------Sequential Create------ --------Random Create-------- -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete-- files:max:min /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP nbs-126.office.n 16 2481 99 +++++ +++ +++++ +++ 2424 99 +++++ +++ 5508 98 single disk nbs-126.office.n 16 2530 99 +++++ +++ +++++ +++ 2437 99 +++++ +++ 6062 100 s/w RAID-1 soft nbs-126.office.n 16 800 99 +++++ +++ 12848 98 807 99 +++++ +++ 2591 99 s/w RAID-1 + LVM nbs-126.office.n 16 2138 98 +++++ +++ 31126 98 2200 99 +++++ +++ 5322 98 h/w RAID-1 nbs-126.office.n 16 2182 99 +++++ +++ 27238 86 2172 98 +++++ +++ 5261 97 h/w RAID-5


Notes:


The last two are with hardware RAID (GDT 4513RZ), and 2Gb RAM instead of 1, but I adjusted
the -s parameter for bonnie++ accordingly.

commandline:
# ./bonnie++ -d /tmp -s 2048 -x2 -uroot
Results shown are for the second run. Machines were otherwise inactive, and carried a
minimum install.

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