On Mon, May 11, 2009 at 10:50:59AM -0400, Theodore Tso wrote: > On Mon, May 11, 2009 at 10:29:51AM -0400, Ric Wheeler wrote: > > The key is not at the FS layer - this is an issue for people who RAID > > these beasts together and want to actually check that the bits are what > > they should be (say doing a checksum validity check for a stripe). > > Good point, yes I can see why they need that. In that case, the > storage device can't just silently truncate a TRIM request; it would > have to expose to the OS its alignment requirements. The risk though > is that more they try push this compleixity into the OS, the higher > the risk that the OS will simply decide not to take advantage of the > functionality. Of course, there is the question why anyone would want > to build a software-raid device on top of a thin-provisioned hardware > storage unit. :-) It's not a problem for people who use Thin Provisioning, it's a problem for people who want to run RAID-5 on top of SSDs. If you have a sector whose reads are indeterminate, your parity for that stripe will always be wrong. -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step." -- 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
