Hi.
2013/8/27 David Brown <[email protected]> > The answer is quite simple - don't use "discard" mounts. They make your > SSD much slower, especially for metadata-heavy operations. > I tend to disagree with this. On the writing operations I saw at least 2x speed with discard / TRIM enabled on dm-crypt LUKS partition. On the another note it's not secure to use TRIM on dm-crypt, because attacker might identify which blocks are free and potentially can detect filesystem. The fix for dm-crypt devices only will be in 3.1.x mainline, so don't think it's gonna be ported in the current 2.6.32 branch. > The problem is that the halfwits that added TRIM to the SATA > specifications made it a synchronous operation, so it blocks all queues > and buffers. They also failed to give it proper semantics, such as > specifying that reading from a TRIM'ed sector would give all zeros. If > the people behind this nonsense had read the SCSI specifications for the > equivalent operation, they would have made a much better TRIM that was > asynchronous, could be queued, and would guarantee reading all zeros > from a TRIM'ed block - which would have been much more useful. > Well, if you won't use TRIM, you'll see in the future write performance degraded all because of the SSD internals. > Off-line TRIM using fstrim is useful, but not essential if you have > bought a half-decent SSD that is not too small, and not too old. So use > fstrim if it works on your setup - but don't worry if it doesn't. It's > very unlikely that you will notice the difference. > I read about it, but don't think it's a proper solution, I'm thinking about trying another virtualization technology instead. LXC seems to be unstable for production yet. Thinking about trying XEN on the more recent kernel. > > Hope that helps, > > David > > > > On 27/08/13 17:10, spameden wrote: > > is it implemented? > > > > I've tried on 3.2.0-4 debian wheezy default kernel it's working just > fine: > > # dmsetup table > > vg0-home: 0 443277312 linear 9:1 25166208 > > home: 0 443273216 crypt aes-cbc-plain > > 0000000000000000000000000000000000000000000000000000000000000000 0 253:2 > > 4096 1 allow_discards > > > > But not on OpenVZ's 2.6.32.xxxx: > > # dmsetup table > > vg0-home: 0 443277312 linear 9:1 25166208 > > home: 0 443273216 crypt aes-cbc-plain > > 0000000000000000000000000000000000000000000000000000000000000000 0 253:2 > > 4096 > > vg0-swap: 0 4194304 linear 9:1 20971904 > > vg0-root: 0 20971520 linear 9:1 384 > > > > > > > > > > > > _______________________________________________ > > Users mailing list > > [email protected] > > https://lists.openvz.org/mailman/listinfo/users > > > >
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