On Sun, Aug 16, 2009 at 10:52:07AM -0500, James Bottomley wrote: > However, the enterprise has been doing UNMAP for a while, so we can draw > inferences from them since the SSD FTL will operate similarly. For > them, UNMAP is the same cost in terms of time regardless of the number > of extents. The reason is that it's moving the blocks from the global > in use list to the global free list. Part of the problem is that this > involves locking and quiescing, so UNMAP ends up being quite expensive > to the array but constant in terms of cost (hence they want as few > unmaps for as many sectors as possible). How are they doing the unmaps? Using something similar to Mark's wiper script and using SG_IO? Because right now we do not actually implement UNMAP support in the kernel. I'd really love to test the XFS batched discard support with a real UNMAP implementation. -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
