On 09/01/13 10:58, Mark Rogers wrote:
How vulnerable is the array to corruption from this process? I'm not too concerned about occassionally having to go through these steps, but I would worry a lot more about losing the data on the array.
I spotted from the logs you're using ext4. Providing your kernel version is 2.6.30 or above it should be as robust as ext3.
(See http://en.wikipedia.org/wiki/Ext4# Delayed_allocation_and_potential_data_loss for why the kernel version if interested)
I think there are more fault-tolerant file-systems, but I don't know if it's worth swapping to one. ext-3/4 are both journalled file systems so should be reasonably fault-tolerant.
As far as I know write caching is disabled, which would be a pretty bad thing under the circumstances (how do I check?), but otherwise is mdadm/RAID5 and ext4 pretty safe?
Two sorts of write caching: Hardware and Software.
I doubt that you could turn Hardware Write Caching off, and from the sounds of it, the disk remains powered even after the whoopsie, so any pending disk writes should get through once sent from disk controller.
Re: Software write caching.
sudo hdparm -i /dev/sdf
will show you if it's on or off. You're looking for "WriteCache=" Repeat for the other drives too!
I got the above from: http://www.linuxquestions.org/questions/debian-26/how-can-i-permanently-turn...
and it also tells you how to turn it off too. HTH