[CentOS] Software RAID1 Disk I/O

Matt lm7812 at gmail.com
Tue Jan 5 23:29:29 UTC 2010

>> I just installed CentOS 5.4 64 bit release on a 1.9ghz CPU with 8gB of
>> RAM.  It has 2 Western Digital 1.5TB SATA2 drives in RAID1.
>> [root at server ~]# df -h
>> Filesystem            Size  Used Avail Use% Mounted on
>> /dev/md2              1.4T  1.4G  1.3T   1% /
>> /dev/md0               99M   19M   76M  20% /boot
>> tmpfs                 4.0G     0  4.0G   0% /dev/shm
>> [root at server ~]#
>> Its barebones right now.  Nothing really running.  I intended to move
>> our current email server over to it eventually.  The thing is slow as
>> mud due to disk I/O though.  I have no idea whats going on.
>> Here is a bit of iostat -x output.
> [...]
>> Does anyone have an idea what I have wrong here?  This is my first
>> software RAID install.  Built a number of Centos servers without RAID
>> and they have all worked fine.
> Did you just create the RAIDs?  It will something that size a few hours to
> complete the initial sync.  Try 'cat /proc/mdstat' to see when the sync
> completes.  Until then, expect to have head contention with anything else
> that might be trying to use the drives.

Here is what I got there.  Md1 is swap I beleive:

[root at server ~]# uptime
 17:20:54 up 7 days,  3:26,  2 users,  load average: 3.41, 2.93, 2.89
[root at server ~]#
[root at server ~]#
[root at server ~]# cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 sdb1[1] sda1[0]
      104320 blocks [2/2] [UU]

md1 : active raid1 sdb2[1] sda2[0]
      8385856 blocks [2/2] [UU]

md2 : active raid1 sdb3[1] sda3[0]
      1456645568 blocks [2/2] [UU]

unused devices: <none>

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