Hey all, Petter Reinholdtsen [2013-08-12 13:04 +0200]: > Hi. Instead of adding discard as a mount option in fstab, perhaps it > is better to add a cron job calling fstrim regularly?
Colin King did some rather extensive benchmarks, and we found that on desktops/servers this is indeed the preferrable default. https://blueprints.launchpad.net/ubuntu/+spec/core-1311-ssd-trimming (I also have the detailled spreadsheets and percentage numbers if anyone is interested) > * Set up cryptsetup to pass TRIM commands to the physical disk > (adding discard to /etc/crypttab) That's "allow-discards" for the record. It's off by default as the cryptsetup authors consider it a potential information leak. I. e. on the physical drive you can map the "used/free" blocks and from their patterns infer the file system type and from their ratio infer how full the file system is. IMHO that's a very small price to pay for keeping your SSD usable in the first place (and yes, I consider reducing write performance from 250 MB/s to 5 MBs/ "useless", each bigger I/O operation completely hangs the computer). If you are worried about that kind of data leak, you would use a hardware-encrypted hard drive anyway, and no cryptsetup. > * Set up LVM to pass on TRIM commands to the underlying device (in > this case a cryptsetup partition) by changing issue_discards from 0 > to 1 in /etc/lvm/lvm.conf. That's orthogonal to discard/fstrim, but should be done anyway. That's http://bugs.debian.org/717313 . > * Set relatime as a file system option for ext3 and ext4 file systems. Agreed (good installer default on rotational drives, too!) > * Run fstrim on every ext3 and ext4 file system every night (from > cron.daily). I just filed http://bugs.debian.org/732054 with a proposed cron job, review/comments appreciated! Thanks, Martin -- Martin Pitt | http://www.piware.de Ubuntu Developer (www.ubuntu.com) | Debian Developer (www.debian.org)
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