RAID 5 reconfiguration to add a hot spare

[meastaugh1]

Hi,

I have a win2k server with a 5 drive backplane, with 5 73gb drives in a RAID5 array. I am considering the possibility of adding a hotspare to decrease downtime.

I'd like to know what options are available which wouldn't involve having to reinstall/restore all the data. Currently approximately 100 of the 290gb is allocated (not sure if this relevant).

Would it be possible to reduce the number of active disks in the array from 5 to 4, and then to make the 5th disk a hot swap. I'm guessing this wouldn't be possible, but just wondering?

Or, would I have to swap the 5 drive backplane for a 10 and then just add another disk? Would this work? Should the SCSI/RAID card just pick up the existing array? I suspect the latter is the only feasible option, but would be more than happy to hear if this not the case.

thanks in advance

 

[PaulSBrum]

Depends on the manufacturer of your disks.

The storage systems I work with will happily work down to 2D+1P. All that happens with bigger groups is the loss to parity gets smaller. ie 3 x 73GB = 146GB useable RAID5 with a loss 0f 50%, 4 x 73GB 210GB useable RAID5 with a loss of 33% etc. The upside of smaller RAID groups is the sparing to the hot spare is quicker.

Reducing the size of an already existing RAID group is always a possibility. Depends on the manufacturer whether you will have to backup your data first and restore. On the kit I work with you can expand without loss, never tried reduction

Rgds