On 2013-04-09 02:40, James Harper wrote:
> I have a server that had 4 x 1.5TB disks installed in a RAID5
> configuration (except /boot is a 'RAID1' across all 4 disks). One of
> the disks failed recently and so was replaced with a 3TB disk,

I'd be very wary of running RAID5 on disks >2TB

Remember that, when you have a disk failure, in order to rebuild the array, it needs to scan every sector of every remaining disk, then write to every sector of the replacement disk.

Compare those number of read & write operations to the Mean Time Between Failures of each disk, and you're (statistically) starting to get close to the point there's a significant risk of a second drive failing prior to the rebuild finishing. (For a given definition of "significant" risk)