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There are different sources and different practices are suggested. I found the following proposals how often one should run fstrim.
What is the optimal option and why? Ubuntu 14.04 uses the first option by default.
TRIM does at least three things:
Now it depends where your priorities are.
For 1), you should not be using fstrim at all, but make use of the discard option of your filesystem. Only if everything is trimmed instantly will the SSD stop copying no longer needed bits of data around. In practice though, it has been shown that preventing write amplification is not that important since SSD are fine with lots of writes.
For 2), using fstrim weekly or even monthly is completely fine. There is no need to use instant discard, or to trim daily - that would be a short-term measure, but this is about keeping the SSD happy in the long-term. But it also depends on your usage: if your filesystem is always full and sees lots of writes, you might need to trim more regularly than if you tend to have lots of free space and not that much writes in your filesystems.
For 3), you should not be using any kind of trim at all. Basically if you expect to be human, making errors, having accidents - like you just deleted your photo collection, whoops - recovery tools like photorec won't work after TRIM because with TRIM everything is gone forever.
From a pure data recovery point of view, SSD is a huge headache. There's too much trim happening in Linux, even without asking you (mkfs implies trim, lvremove/lvresize/... might if issue_discards, some partitioners might be having ideas, ...). Suddenly previously reversible actions become irreversible, all for the sake of getting a few more points in some filesystem benchmark...
If you decide on fstrim you should know where the cron job is located so you can disable it when you have an accident, that way you get a compromise between 2) and 3). In general with SSD you should make sure you have good backups, they are even more important than with HDD since you have lesser chance of recovery on SSD.
discard is suboptimal performance-wise: blog.neutrino.es/2013/… and patrick-nagel.net/blog/archives/337
Jul 24, 2015 at 8:04
discard=async is essentially still the same as instant discard (delayed by seconds/minutes, not days/weeks/months). It's an implementation detail of btrfs, other filesystems like XFS may be using async discard anyway, without providing a separate mount option. So there is no difference other than performance impact of the discard operation itself. fstrim also has a few performance related options, you can limit it to a specific region or set a minimum size, that way fstrim finishes faster (at the cost of not trimming everything).
Apr 2, 2022 at 8:47
man fstrim in Ubuntu 16.04 has
Running fstrim frequently, or even using mount -o discard, might nega‐ tively affect the lifetime of poor-quality SSD devices. For most desk‐ top and server systems the sufficient trimming frequency is once a week.
