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Raid 3 for clone luns?
After the purchace of some new 500Gb SATA drives for our CX700 I'm thinking of creating a RAID3 group on them. This group would only be used for standard 1 sync/fracture a day Clones and RMSE clones.
My questions are:-
What disk space utilisation should I expect from a RAID3 goup as opposed to RAID5?
What would rebuild times be on a RAID3 goup as opposed to RAID5 in the event of a failed disk? also what expected impact whist rebuilding?
Many thanks...
Ian
My questions are:-
What disk space utilisation should I expect from a RAID3 goup as opposed to RAID5?
What would rebuild times be on a RAID3 goup as opposed to RAID5 in the event of a failed disk? also what expected impact whist rebuilding?
Many thanks...
Ian
GlenH
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December 5th, 2006 20:00
Raid 3 will give you the same usable capacity as Raid 5 (1 drive used for parity protection)
A point to note is that Raid 3 can only be configured on 5 or 9 drives ie: 4+1 or 8+1
You need to be very careful using raid 3 for clone volumes as when you synchronise the clone, the host write I/O to the source LUN will perform at the speed of the slowest configuration (source or clone) - if it's exchange and doing lots of small writes, this may be very bad as raid 3 is not suited to that type of workload.
Raid 3 rebuilds used to be alot faster than Raid 5 until Flare 19 introduced significant improvements to ATA Raid 5 rebuild times (4x improvement)
The actual time taken will depend on the size of the raid group, the load of the array and if there is any workload on the LUN's associated with the raid group being rebuilt. A very rough estimate would be around 8hrs.
Glen