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Write Balance
On our VMAX, using FAST VP, noticed that a set of SATA disks was using roughly 50% less capacity than the other SATA disks. We started a Write Balance on the pool, but have only observed the disks with a higher capacity are increasing in used space and the disks with the 50% less are decreasing in used space, although very slowly. Is there any details on how the Write Balancing works? The process has been running for 6 days, and we were under the impression all the disks would get to an even point.
We have the rebalance variance set to the default of 1.
Quincy561
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Posted September 19th, 2013 07:00
The rebalance is done on capacity. If you have mixed disk sizes in the same pool, they both will be balanced to the same percentage of capacity. So your larger disks will have more capacity used and more IOPs. This is why we do not recommend mixing drive sizes in any given VP pool.