Hey people
I have recently migrated my file server over to a HP Microserver. The server has two 1TB disks, in a software RAID-1 array, using MDADM. When I migrated simply moved the mirrored disks over, from the old server Ubuntu 9.10 (server) to the new one 10.04.1 (server).
I Have recently noticed that write speed to the RAID array is *VERY* slow. In the order of 1-2MB/s order of magnitude (more info below). Now obviously this is not optimal performance to say the least. I have checked a few things, CPU utilisation is not abnormal (<5%) nor is memory / swap. When I took a disk out and rebuilt the array, with only one disk (tried both) performance was as to be expected (write speed >~70MB/s) The read speed seems to be unaffected however!
Creating a file on the single (non-raid) disk, is fine:
However, copying the 1GB file to the array (mounted on /storage/big/) takes ~25mins, (~ 0.6MB/s) which is not normal
Creating the file on the array (from the kernel /dev/zero, no other storage involved), is again very slow:
Reading from the array however, everything runs fine!:
As is copying from the array to the single disk
Also here is the output of 'cat /proc/mdstat'
As mentioned above when I remove a disk, and then mount a single drive from the array performance is normal, with either disk, whilst I understand that write speeds to RAID-1 mirrors might not be blazing, I am certain that something is amiss here!
I'm tempted to think that there is something funny going on with the storage subsystem, as copying from the single disk to the array is slower than creating a file from /dev/zero to the array using DD..
Either way I can't try the array in another computer right now, so I though I was ask to see if people have seen anything like this!
At the moment I'm not sure if it is something strange to do with having simply chucked the mirrored array into the new server, perhaps a different version of MDADM? I'm wondering if it's worth backing up and starting from scratch! Anyhow this has really got me scratching my head, and its a bit of a pain! Any help here would be awesome, e-cookies at the ready! Cheers
SS
I have recently migrated my file server over to a HP Microserver. The server has two 1TB disks, in a software RAID-1 array, using MDADM. When I migrated simply moved the mirrored disks over, from the old server Ubuntu 9.10 (server) to the new one 10.04.1 (server).
I Have recently noticed that write speed to the RAID array is *VERY* slow. In the order of 1-2MB/s order of magnitude (more info below). Now obviously this is not optimal performance to say the least. I have checked a few things, CPU utilisation is not abnormal (<5%) nor is memory / swap. When I took a disk out and rebuilt the array, with only one disk (tried both) performance was as to be expected (write speed >~70MB/s) The read speed seems to be unaffected however!
Creating a file on the single (non-raid) disk, is fine:
Code:
root@BigBertha:/# dd if=/dev/zero of=ddfile.big bs=1MB count=1k
1024+0 records in
1024+0 records out
1024000000 bytes (1.0 GB) copied, 14.9 s, 68.7 MB/s
Code:
root@BigBertha:/# time cp ddfile.big /storage/big/
real 25m51.021s
user 0m0.128s
sys 0m10.957s
Code:
root@BigBertha:/storage/big# dd if=/dev/zero of=ddfile.big bs=1MB count=1k
1024+0 records in
1024+0 records out
1024000000 bytes (1.0 GB) copied, 71.4943 s, 14.3 MB/s
Code:
root@BigBertha:/storage/big# dd if=ddfile.big of=/dev/null
2000000+0 records in
2000000+0 records out
1024000000 bytes (1.0 GB) copied, 12.4544 s, 82.2 MB/s
Code:
root@BigBertha:/storage/big# time cp ddfile.big ~
real 0m13.547s
user 0m0.040s
sys 0m4.156s
Code:
root@BigBertha:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : active raid1 sdc1[0] sdb1[1]
976759936 blocks [2/2] [UU]
unused devices: <none>I'm tempted to think that there is something funny going on with the storage subsystem, as copying from the single disk to the array is slower than creating a file from /dev/zero to the array using DD..
Either way I can't try the array in another computer right now, so I though I was ask to see if people have seen anything like this!
At the moment I'm not sure if it is something strange to do with having simply chucked the mirrored array into the new server, perhaps a different version of MDADM? I'm wondering if it's worth backing up and starting from scratch! Anyhow this has really got me scratching my head, and its a bit of a pain! Any help here would be awesome, e-cookies at the ready! Cheers
SS