Honestly, the above "Manual Trim" sounds like marketing tripe.
From the manufacturers of Sandforce controllers (and interestingly, quoted on the Disk Sensei website!), "Garbage collection without TRIM will always be moving all invalid data during the GC process acting like the SSD is operating at full capacity. Only the TRIM command can identify the invalid data and improve performance"
Trim is a specific instruction that is sent to the SSD and the Apple driver doesn't send it, period. A modified driver (kernel extension) can do, but to load that you need to disable kext signing.
All modern SSD's do garbage collection. Without being sent the Trim command (which the Apple driver will never do), they don't know what is real data and what is not. "Manual Trim" writing zeros into available blocks will not help, since the drive has *no way* of knowing whether this is real data or not. It will run garbage collection on all the data, including the pages of zeros; not helpful at all in reducing write amplification, which is one of the prime benefits of Trim. In fact it's downright detrimental since (a) you are needless writing garbage to the SSD in the first place and (b) the SSD then has to do lots of reading and writing to tidy it all up. I would suggest this "Manual Trim" option - which is not Trim at all - should be avoided.
You basically have 2 simple choices; either disable kext signing, which the inherent (but not enormous) risks that involves (previous OS X versions didn't have kext signing anyway); or let the drive manage itself and accept that it will wear out somewhat faster and may not perform at its absolute best.
Whether these last two drawbacks matter in the real world will depend on what you use the drive for. If it's for mainly read-access with little writing going on, it probably doesn't matter at all. For a boot drive, I think it does matter.
There is a 3rd, more invasion option however, which is to periodically wipe the drive with a ATA Secure-Erase command, destroying all data and returning the drive to factory performance levels. And then restoring from a back up. You could do this every few months if you wanted to.
Is it true that Trim information is sent to an SSD, via the Apple driver, if the drive is an OEM Apple device? Looking for clarification on this.
I am using an older M4 Crucial drive, as a boot drive, in a Late 2008 MacBook Pro (SATA 3Gb). I installed it because the computer was very slow, and even this slower drive, on the 3Gb, interface has made this machine acceptably fast. Even though it's an older model, it does support GC.
Now I am confused... According to the Crucial website, GC only works when the drive is idle. It was recommended to boot the machine into Startup Mode as the SSD will then be in an "idle" state where GC will properly run. I will look for the link, and post it here.
Thanks for the info. I am going to email the author of the utility, and ask him for comment. I would like to know what the deal is, and he has been very responsive in the past.
EDIT: BTW, I don't think that the M4 uses a Sandforce controller. Is what you have stated above still applicable? I believe Sandforce controllers do compression, on the fly - would this matter?
EDIT 2: From the
Crucial site posted by a Crucial Moderator:
"On a Mac, press the Options key while powering on to enter the Startup Manager screen. Leaving the Mac on that screen provides the SSD with power but keeps it in an idle state so Garbage Collection can function, just like the BIOS screen on a Windows laptop."