[mythtv-users] OT Hardware RAID 5 Recommendations

Matthew McClement mythtv at macker.co.uk
Fri Dec 15 13:31:55 UTC 2006

John Clabaugh wrote:
> Speaking of growing a RAID 5 array, has anyone tried this in Linux
> with software RAID?  http://scotgate.org/?p=107 - (Growing a RAID5
> array - MDADM)

I've done it a few times using the evms RAID5 growing stuff(it's been 
supported for a while and does have the ability to revert in case of a 
failure mid-grow). I think the only real risk is the initial handful of 
stripes being written. AFAIK it grows the array by reading a 
stripe+enough extra data to fill the new disk(s), recalculating the 
parity and writing it out. Initially this needs to be done by destroying 
the existing stripes but after the initial lot it can start writing 
stripes without stomping on existing data.

But as a word of warning, it's slooooooooow. 4x250GB to 6x250GB took 
about 40 hours. 6x250GB to 8x250GB took about 70 hours. This was on an 
otherwise idle dualcore 2.8Ghz P4 with a PCI-X SATA card on a 
100Mhz/64bit bus so no bus/CPU contention.


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