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I'm upgrading a 2010 Macbook with an Intel 730 SSD. Since Trim Enabler is still available but more risk, I'm trying to get by with just Disk Utility.

My question was prompted by this hint which seems to imply that "Disk Repair" will perform a one-time TRIM. Using either a reminder or an automated script, I could run Repair Disk once a week or once a month to get the benefits of TRIM.

There is a similar question at Creative solutions to work around kext signing issue in Yosemite? that does not answer my question.

John Schmitt
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  • @Buscar웃 Your comment is more of a new question than a comment on the existing question. TRIM is not like defragmentation: the “normal” way is to do it as soon as a block is freed, not periodically, and it affects the disk itself rather than the filesystem on it. – Pascal Cuoq Jan 03 '15 at 21:41
  • TRIM and defragmenting are not the same. See http://en.wikipedia.org/wiki/Defragmentation and http://en.wikipedia.org/wiki/Trim_(computing) ; Defragging is about moving logical filesystem blocks closer together physically to reduce disk seek times. Trimming is about proactively 'erasing' free'd blocks since SSDs have much different performance characteristics for 'erase' behaviours than traditional spinning disks. – John Schmitt Jan 03 '15 at 21:46
  • Just asked a similar question here. – n1000 Jan 03 '15 at 21:56
  • Don't understand the downvotes. – John Schmitt Jan 04 '15 at 00:31

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Did you notice that the interesting bits in the discussion seem to point to Disk Repair having performed a TRIM because Trim Enabler was installed? User jimsander says:

My guess is it's a result of the 3rd party TRIM enabler - just did Disk Utility --> Repair on my machine (MacBook 2008 w/ Lion + Crucial SSD) and it didn't say it did a TRIM.

It would not make much sense if Disk Repair made a TRIM happen without Trim Enabler, because what is lacking by default for non-Apple SSDs (and that Trim Enabler provides) is driver support for TRIM. Disk Repair accesses the hardrives through the same driver that the filesystem implementation uses in normal operation, so it won't do the one-time TRIM without the same driver support that would allow the filesystem implementation to trim immediately.

Pascal Cuoq
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  • Further down in that discussion are posts that say a) TRIM is no longer needed and b) MacOS X does TRIM natively. So, not authoritative and also contradictory. Sadly, the apple docs are silent on this which makes me think that you and that poster "jimsander" might well be correct. – John Schmitt Jan 03 '15 at 22:05
  • @JohnSchmitt As to whether TRIM is needed: it provides information to the disk that the disk cannot obtain in any other way short of reverse-engineering the filesystem used on it (information of the sort “although I am not changing the contents of this block, I am no longer interested in them and promise never to read them again, so you can clear the block for reuse now”. This is useful information because of how SSD disks work and regardless of palliative measures they may have in place to work well even without that information.) – Pascal Cuoq Jan 03 '15 at 22:10