laptop advice time...

[D. Hugh Redelmeier]

| From: Jamon Camisso <jamon.camisso-H217xnMUJC0sA/PxXw9srA at public.gmane.org>

| I have a fully luks encrypted disk with TRIM support running Debian. It
| takes 3 things:
| 
| 1) add these options to GRUB_CMDLINE_LINUX: allow-discards root_trim=yes
| 2) add "discard" to relevant partitions in /etc/crypttab
| 3) issue periodic fstrim commands. I do this once a day with cron

I would have thought that 2 and 3 do the same job in different ways.
2 acts earlier, so 3 would be redundant.

I admit that I don't really understand the subtleties of TRIM on
different abstraction layers (real disk vs virtual decrypted disk).

With luks, is there a simple one-to-one correspondence between encrypted 
and decrypted blocks?

I would be surprised if discard and fstrim are both useful: one or the
other should do the job.  I don't know which is better, but some
advocate fstrim over discard and I don't remember any advocating
discard over fstrim.

| From: Lennart Sorensen <lsorense-1wCw9BSqJbv44Nm34jS7GywD8/FfD2ys at public.gmane.org>

| TRIM helps performance, but other than that should not actually affect
| the lifespan of the device.

I don't think that that is correct.  TRIM avoids useless copying, and
all writes are likely to cause SSD wear.
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