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Re: TRIM

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On 17/09/2025 11:05, Davey wrote:
> So, as one who knew nothing of trimming before this conversation
> started, I am now as confused as ever as to what is the best strategy
> to employ.

That's partly because it's really difficult to give an unambiguously 
correct answer. One size doesn't fit all.

> Should I set up a regular fstrim event, and if so, how frequently? Once
> per week, once per month, or after a heavy data writing session?

Hard to say as we don't know the make/model of your SSD, how old it is, 
nor how full it is.

Modern SSDs are designed to work without TRIM ... nevertheless using 
TRIM may be beneficial, and can help reduce SSD wear.

The benefit you'll get from TRIM is more if your SSD is close to full. 
This is because as the SSD fills up there are fewer empty pages to which 
the controller can write new data and so more work for garbage 
collection to do. Better-quality SSDs (newer designs, more reputable 
brands) have cleverer software that works better without TRIM, but that 
can also make better use of information from TRIM.

I would say that the "best" thing to do is to let the filesystem handle 
TRIM on-the-fly and forget about scheduled calls to fstrim. That's what 
I'm doing and nothing has bitten me yet ... but I may just be lucky. The 
SSD I use the most is a PNY device a year or so old so I expect it to be 
reasonably current and performant.

Older and cheaper SSDs are reported to experience problems when doing 
TRIM on the fly, and if you have one of those then you would be better 
advised to use fstrim instead. Don't ask me which SSDs fall into this 
category because I can't give you a list.

The time that fstrim will be most beneficial is not after writing data 
to the SSD, it's after erasing data from the SSD ... so if you delete a 
lot of files, or if you edit a lot of files (so that a new version is 
created and the old one is deleted), there will be a lot of sectors to 
TRIM. Just writing new data to the disk doesn't create unused sectors, 
so TRIM won't help.

The general advice I see from people advocating the schedules use of 
fstrim is to do it once a week, unless you have reason to believe that 
you need to do it more often. I know that doesn't help much.

fstrim doesn't take very long, and doesn't add to SSD wear, so there's 
no harm in running more often, it just won't add benefit.

One thing I would add: If you decide to turn on on-the-fly TRIMming (by 
adding "discard" to /etc/fstab) it's worth running fstrim once first, to 
bring the SSD up to date with what's actually in use in the flash 
memory, and what isn't. It should stay current by itself after that.

Does any of this help?

-- 
Cheers,
  Daniel.

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Here we go again Davey <davey@example.invalid> - 2025-09-02 11:03 +0100
  Re: Here we go again Davey <davey@example.invalid> - 2025-09-03 08:57 +0100
    Re: Here we go again Daniel James <daniel@me.invalid> - 2025-09-03 16:49 +0100
      Re: Here we go again Theo <theom+news@chiark.greenend.org.uk> - 2025-09-03 17:21 +0100
        Re: Here we go again Davey <davey@example.invalid> - 2025-09-03 17:48 +0100
          Re: Here we go again Theo <theom+news@chiark.greenend.org.uk> - 2025-09-03 18:20 +0100
            Re: Here we go again Davey <davey@example.invalid> - 2025-09-03 20:10 +0100
            Re: Here we go again Davey <davey@example.invalid> - 2025-09-03 20:50 +0100
            Re: Here we go again Davey <davey@example.invalid> - 2025-09-04 11:35 +0100
              Re: Here we go again Daniel James <daniel@me.invalid> - 2025-09-04 17:30 +0100
                Re: Here we go again Davey <davey@example.invalid> - 2025-09-04 19:52 +0100
                Re: Here we go again Davey <davey@example.invalid> - 2025-09-05 23:49 +0100
                Re: Here we go again Davey <davey@example.invalid> - 2025-09-08 11:50 +0100
                Re: Here we go again "Vincent Coen" <VBCoen@gmail.com> - 2025-09-08 16:11 +0100
                Re: Here we go again Davey <davey@example.invalid> - 2025-09-08 17:28 +0100
                TRIM (Was: Here we go again) Daniel James <daniel@me.invalid> - 2025-09-15 16:00 +0100
                Re: TRIM (Was: Here we go again) Davey <davey@example.invalid> - 2025-09-15 17:30 +0100
                Re: TRIM Richard Kettlewell <invalid@invalid.invalid> - 2025-09-17 08:43 +0100
                Re: TRIM Daniel James <daniel@me.invalid> - 2025-09-17 10:30 +0100
                Re: TRIM Davey <davey@example.invalid> - 2025-09-17 11:05 +0100
                Re: TRIM Daniel James <daniel@me.invalid> - 2025-09-17 15:12 +0100
                Re: TRIM Davey <davey@example.invalid> - 2025-09-17 15:54 +0100
                Re: Here we go again Davey <davey@example.invalid> - 2025-09-09 09:04 +0100
                Re: Here we go again "Vincent Coen" <VBCoen@gmail.com> - 2025-09-09 12:19 +0100
                Re: Here we go again Davey <davey@example.invalid> - 2025-09-09 18:03 +0100
                Re: Here we go again "Vincent Coen" <VBCoen@gmail.com> - 2025-09-09 22:02 +0100
                Re: Here we go again Davey <davey@example.invalid> - 2025-09-10 00:14 +0100
                Re: Here we go again -Update Davey <davey@example.invalid> - 2025-09-11 17:12 +0100
                Re: Here we go again -Update Davey <davey@example.invalid> - 2025-09-21 16:10 +0100
                Re: Here we go again -Update "Vincent Coen" <VBCoen@gmail.com> - 2025-09-22 01:41 +0100
                Re: Here we go again -Update Davey <davey@example.invalid> - 2025-09-22 09:29 +0100
                Re: Here we go again Davey <davey@example.invalid> - 2025-09-10 12:43 +0100
                Re: Here we go again Theo <theom+news@chiark.greenend.org.uk> - 2025-09-08 21:33 +0100
              Re: Here we go again Daniel James <daniel@me.invalid> - 2025-09-04 20:07 +0100
                Re: Here we go again Davey <davey@example.invalid> - 2025-09-05 02:47 +0100
          Re: Here we go again Gordon <Gordon@leaf.net.nz> - 2025-09-03 23:46 +0000
            Re: Here we go again Davey <davey@example.invalid> - 2025-09-04 09:36 +0100
        Re: Here we go again Gordon <Gordon@leaf.net.nz> - 2025-09-03 23:31 +0000

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