Very bad (under 30MB/s) with software RAID1
 

OK this is what I have done, I am up for any suggestion to fix this. Its a new install so anything goes.

I have a Dell Poweredge T20 and I put 2 Tosiba P300 2TB drives in it. I simply wanted to RAID1 the whole lot for resilience. I did the Ubuntu LTS 14.04 install and the only way I could do this is create a RAID1 volume and make swap, /boot and / and a data partition (/data) all in it.

It booted OK but seemed slow. Its the Pentium G3220 T20, which I know is not very powerful, but its a low use server. Ive installed stuff on much older boxes and it did not seem as sluggish. Its a very minimal server installation, only thing I added was openssh.

So I tried dd and got:

ben@sun:~$ dd if=/dev/zero of=test-file bs=32
^C23117888+0 records in
23117888+0 records out
739772416 bytes (740 MB) copied, 25.8429 s, 28.6 MB/s

Which is pitiful, I would expect 3 times that.

So I did top during the dd and it was maxing out one of the CPUs, so I guess that is the issue. Does software RAID normally use this much CPU or is there something else wrong?

Ben

OK, its because it is doing a resync.

I assume that is the solution. Thanks for the update and solution.