Re: how to enable trim for an external encrypted SSD?
- Date: Mon, 6 Nov 2017 15:43:00 -0500
- From: Michael Stone <mstone@xxxxxxxxxx>
- Subject: Re: how to enable trim for an external encrypted SSD?
On Tue, Nov 07, 2017 at 01:00:54AM +0500, Alexander V. Makartsev wrote:
Now I wonder, why would anyone want to use TRIM feature on a portable SSD,
especially on an encrypted one?
Isn't this feature only increases drive wear, offering next to nothing as a
benefit in return?
I don't use TRIM feature on my systems because of that, and hope for a firmware
of modern SSD will manage everything automatically. Am I wrong?
TRIM should reduce, not increase, drive wear. (Since the drive knows
that a particular block is unusued, it can write directly instead
of having to read and rewrite an entire erase group.) It should also
increase performance by increasing the free pool on the drive and reduce
the garbage collection pressure. The magnitude of any benefits depends
heavily on how the drive is used and how the firmware implements its
writing and garbage collection routines.
A possible negative is that some drives have bugs in their TRIM
implementation (known bad drives are blacklisted). Also, enabling TRIM
at the filesystem level can reduce performance depending on the drive's
implementation and the read/write patterns on the filesystem. (Issuing
large numbers of small TRIM operations can negatively affect
performance.) That disadvantage can be avoided by running fstrim in
batch rather than having the filesystem TRIM as files are deleted.