Slow SSD boots - whats wrong?

Discussion in 'Mac mini' started by AT0MAC, Aug 16, 2012.

  1. AT0MAC macrumors regular


    Jun 4, 2011
    Copenhagen, Denmark
    I have two Intel 520 Series SSDs in my Mac mini because of speed and silence - but here 6 months after installing it's getting a really slow boot time compared to freshly installed.

    Earlier it was 18 seconds till login, now it's 48.
    How could it gain 30 seconds on 6 months?

    Is there anything wrong?

    I only use one SSD as the main drive, the other is for recently used files - having backup and external storage for more important things.
  2. surroundfan macrumors 6502

    Nov 22, 2005
    Melbourne, Australia
    You've set the SSD you want to boot from as the startup disk in System Preferences? You've enabled Trim?
  3. Ifti macrumors 68000

    Dec 14, 2010
    SSDs slow down over time if they are not cleaned up by using TRIM.

    Try the suggestions mentioned by SurroundFan - make sure the SSD is set as the startup disc as this will shave a lot of time off since the system does not have to search for a startup disc before loading the OS.

    If this is OK and things are still slow, install Trim Enabler and enable TRIM on the drive. Leave it for a whiel and you should notice the drive speeds back up over time as its cleaned.
  4. AT0MAC thread starter macrumors regular


    Jun 4, 2011
    Copenhagen, Denmark
    I have not enabled trim as the Intel should have a perfectly good garbage collection.
    Luckily you were right, it was not set as boot disc since I last backed up the entire computer and tested my backup - so it have been looking for a startup volume ever since... Doh!

    Thanks :)
  5. Chippy99 macrumors 6502a

    Apr 28, 2012
    Trim and GC are different things and go hand in hand. You should use both if you can.

    If you do not have Trim enabled, it does not matter how good the drives own GC is, it has no way of knowing what data is deleted data and will spend its time tidying up invalid data.

    To not use Trim is to abuse your SSD.

    Staggering how many people do not understand this.
  6. CausticPuppy macrumors 65816

    May 1, 2012

    See the following link - it applies to Crucial but other drives with garbage collection shouldn't be any different.

  7. Chippy99, Aug 17, 2012
    Last edited: Aug 17, 2012

    Chippy99 macrumors 6502a

    Apr 28, 2012
    Pure marketing nonsense from Crucial I am afraid. Let me explain in VERY simple terms.

    When your OS updates or deletes a file, it updates the directory to say that the file is deleted. In the case of an update, it writes the new updated file somewhere else as well. The file is not in reality deleted - hence the various utilities you can get to recover deleted data.

    But it does not tell the disk controller that the delete has happened. As far as the disk is concerned the deleted file is still valid and it cannot differentiate between the deleted file and current, valid files.

    That is what the TRIM command is for. Its the OS telling the disk controller that file xyz is now deleted.

    All SSDs have garbage collection. Crucial's marketing nonsense is just that, nonsense. They ALL have garbage collection. How they work various according the controller and how the manufacturer has implemented it. But in very simple terms all it does is tidies up data into nice neat blocks so that when you need to do a write, it can write to nice empty cells and can do so as fast as possible.

    The problem is, when it is doing this "tidying up", unless the OS has told it what data is no longer valid (by issuing a TRIM command) it has no way of knowing, so it goes around reading and writing both good and bad data and consolidating all of it, including the bad data that has been deleted as far as the OS is concerned.

    So what?

    Well consider editing a 10MB PowerPoint presentation. All the time PowerPoint is doing background saves. Over a 2 hour period working on your presentation, PP will have saved the file 12 times, each time deleting the last save and saving a new copy. There will be 100MB+ of deleted data lying around and 10MB of valid data. The SSD will do its garbage collection on 110MB of data and use up 110MB of space when only 10MB should actually be used.

    Now think of this happening all the time with your OS updating logs, temporary cache files, old documents etc etc etc. There is a HUGE amount of deleted data still sitting on your SSD and the SSD will busily go about its business tidying all of that up with loads of background reads and writes that need not be happening.

    So what does this mean? It means that without TRIM, (a) your drive is much more full than it appears, and write times will slowly deteriorate as the drive struggles to find free space to write to. And (b) the drive will wear out much more quickly because it is doing much more writing than it should be doing. (It is also doing "wear levelling" to spread the writes out across the disk, but it is doing that with loads of bad data when it need not be doing so.)

    Conclusion: You need TRIM for an SSD to work at its best. There is no escaping this fact. The SSD manufacturers are not all going to tell you this, especially if there is no TRIM support for their drive. But that's the fact. Garbage collection and TRIM are NOT the same thing and you need both for your drive to perform properly.

    I was being kind to Crucial calling that link marketing nonsense. In fact it's just plain wrong. Sandforce - who make the controller Crucial are using - tell you that you need both TRIM and garbage collection and that GC alone is not sufficient.
  8. drbrog macrumors member

    Apr 29, 2005
    How does one enable TRIM or confirm that TRIM is enabled? I have a new retina MBP and am having no problems whatsoever but am just curious.
  9. CausticPuppy macrumors 65816

    May 1, 2012
    OK, first of all the Crucial M4 uses a Marvell controller, not Sandforce...

    Some good info here, and the Marvell drives seem to do better than Sandforce when TRIM isn't working.

    Whether TRIM is enabled or not, a drive is never going to come close to its rewrite cycle limit over the lifespan of the drive, unless your are running a database on it or something and the drive is nearly full all the time.
  10. Chippy99 macrumors 6502a

    Apr 28, 2012
    OK, fair point. Changes nothing though. Without TRIM, Marvell controllers don't know what data has been deleted any better than Sandforce ones. Neither have any clue and nor can they have.


    But it doesn't change the fact that the drive is more full than it should be, and it is spending time moving deleted data around and you have less free space to write to. If you have a 256GB drive with a 30GB OS install on it and nothing else, this probably doesn't matter much. But running a 128GB disk with a load of other stuff on there at say 75% capacity, and yes, you will notice big time if TRIM is not enabled.

    But anyway, none of this matters. The debate is whether you should enable TRIM if you can, and the answer is YES. Anything else is a compromise and the drive is not working to its optimum.

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