Re: fstrim and SSDs and cron; was: Re: cron-service

[Danny Milosavljevic]

> I had never thought of it, but maybe it’s a good idea.  How do other
> distros handle it?

On <https://askubuntu.com/questions/18903/how-to-enable-trim> they say:
>Ubuntu 14.10 onwards:
>In Ubuntu 14.10 and 15.04, TRIMming happens automatically every week on all 
>SSDs supported by fstrim.
>$ tail -n1 /etc/cron.weekly/fstrim 
>/sbin/fstrim --all || true




>Automatic TRIM (Deprecated, Slow):
> [fstab...]

>Encrypted Filesystems
>The last step is not enough though. As long as LUKS is not aware that you want 
>to use TRIM it will effectively block all TRIM operations coming from the LVM 
>partition's file system, for security reasons. Add discard parameter to the 
>cryptdevice options in /etc/crypttab to make LUKS accept the discard behavior 
>of the LVM partition.
>sda5_crypt UUID=e364d03f-[...]6cd7e none luks,discard

More info about the latter:

http://blog.neutrino.es/2013/howto-properly-activate-trim-for-your-ssd-on-linux-fstrim-lvm-and-dmcrypt/

Note that guix 
/gnu/store/8vg9124cgm8d36zsy9ldcw53b1vrfy2w-lvm2-2.02.109/etc/lvm/lvm.conf 
explicitly disables (!) "discard".