On Fri, Dec 07, 2012 at 02:27:43PM -0700, Theodore Ts'o wrote: > On Fri, Dec 07, 2012 at 04:09:32PM -0500, Chris Mason wrote: > > Persistent trim is what I had in mind, but there are other ideas that do > > imply a change in behavior as well. Can we safely assume this feature > > won't matter on spinning media? New features like persistent > > trim do make it much easier to solve securely, and using a bit for it > > means we can toss back an error to the app if the underlying storage > > isn't safe. > > We originally implemented no hide stale for spinning media. Some > folks have claimed that for XFS their superior technology means that > no hide stale doesn't buy them anything for HDD's. I'm not entirely > sure I buy this, since if you need to update metadata, it means at > least one extra seek for each random write into 4k preallocated space, > and 7200 RPM disks only have about 200 seeks per second. True, 7200 RPM disks are slow, but even allowing them to expose stale data just makes them a little less slow. I know it's against the rules to pretend that disks don't matter. But really, once you're doing random IO into a spindle you've given up on performance anyway. -chris -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
