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

[Ron Arts <raarts@netland.nl>]

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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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