Software Raid 1 - Rather Slow During Raid 1 Recovery

May 20, 2009

I have a new server and it is rather slow during raid 1 recovery after system installed

CPU: Intel Core2Duo E5200 Dual Core, 2.5Ghz, 2MB Cache, 800Mhz FSB
Memory: 4GB DDR RAM
Hard Disk 1: 500GB SATA-2 16MB Cache
Hard Disk 2: 500GB SATA-2 16MB Cache

root@server [~]# cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 sdb1[1] sda1[0]
256896 blocks [2/2] [UU]

md1 : active raid1 sdb2[1] sda2[0]
2096384 blocks [2/2] [UU]

md2 : active raid1 sdb4[2] sda4[0]
480608448 blocks [2/1] [U_]
[=======>.............] recovery = 36.7% (176477376/480608448) finish=1437.6min speed=3445K/sec

the sync speed is just 3.4Mb/second and the total hours needs to be more than 40 hours

Also the server load is very high (nobody uses it)

root@server [~]# top
top - 07:00:14 up 16:55, 1 user, load average: 1.88, 1.41, 1.34
Tasks: 120 total, 1 running, 119 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.0%us, 0.2%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.0%hi, 0.2%si, 0.0%st
Mem: 4148632k total, 747768k used, 3400864k free, 17508k buffers
Swap: 5421928k total, 0k used, 5421928k free, 569252k cached

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Quote:

Today we are going to conduct a detailed study of RAIDability of contemporary 400GB hard drives on a new level. We will take two "professional" drives from Seagate and Western Digital and four ordinary "desktop" drives for our investigation. The detailed performance analysis and some useful hints on building RAID arrays are in our new detailed article.

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I installed CentOS 5.0 and I configured it with software RAID 1, two disks - one IDE 160 GB and one SATA 40 GB.

Here is the setup of the disks:

RAID:
~40 GB RAID 1 md0 ext3
~500 MB RAID 1 md1 swap

Disk1:
~40 gb software raid md0
~500 mb software raid md1

Disk 2:
~40 gb software raid md0
~500 mb software raid md1

After the installation I noticed that the server was very slow so I did a performace test on disk 2, here is the result:
hdparm -tT /dev/hdd first gave me:
Timing buffered disk reads: 6 MB in 3.52 seconds = 1.70 MB/sec
Timing cached reads: 488 MB in 6.92 seconds = 70.57 MB/sec

then gave me:
Timing cached reads: 392 MB in 2.01 seconds = 195.01 MB/sec
Timing buffered disk reads: 2 MB in 3.62 seconds = 566.16 kB/sec

So I assumed something was wrong with the disk and replaced it with an 80 GB IDE disk (same setup as before) and got the following results:
hdparm -tT /dev/hdd:
Timing cached reads: 4 MB in 4.69 seconds = 872.73 kB/sec
Timing buffered disk reads: 6 MB in 3.72 seconds = 1.61 MB/sec

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[url]

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[url]

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Version 1.03b ------Sequential Output------ --Sequential Input- --Random-
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