SSD: OSX vs Win7

Discussion in 'MacBook Air' started by JesseW6889, Dec 30, 2010.

  1. JesseW6889 macrumors 6502

    Joined:
    Dec 12, 2010
    #1
    So... From what I'm reading, OSX on SSD is somehow immune from needing a trim command to manage re-writing erased data on a 'used' SSD.

    Is that true? Or... if I 'fill up' my SSD in OSX, would it make sense to format, install Windows 7 and let the trim clean up the SSD? Is that how it works?

    I don't know much about any of this so, any guidance... I just don't want my air to lose any of its 'airiness'

    This is my first Mac, so I'm also just expecting things to get bogged down the more I use it... Does that happen with macs also?

    Sorry, I'll stop changing the subject!
     
  2. crazyyankeefan macrumors regular

    Joined:
    Jul 27, 2008
    Location:
    Albany, NY
    #2
    I only have limited knowledge about SSD, but from what I know, OSX doesn't need to reboot as often as Windows, nor does it need any defrag. And for SSD, the less you have to re-write over the same "sector" of the storage, the better, so defrag is actually worse for SSD (ok...I'm not completely certain about this).

    Anyway, in short, if you hope to keep your SSD in top performance speed, the best way to use your MBA is to set up an external hard drive for storage (music, photos, movies, etc), and use the internal SSD strictly for the OSX only, or some essential applications and documents.
     
  3. KPOM macrumors G5

    Joined:
    Oct 23, 2010
    #3
    OS X does not support TRIM, but it may be coming later. Windows 7 is the most SSD-aware version of Windows yet, and it will automatically turn off things like background defragmenting (that are on by default in Vista) if it detects an SSD. I think that Microsoft just spent more time adding these features and overall has made more of an effort specific to SSDs than Apple has with OS X to date. The new exFAT file system was developed by Microsoft specifically for flash storage. Fortunately, Apple has licensed this, too. That said, I have read that the HFS+ file system is a bit better than the NTFS file system at minimizing write activity on SSDs.

    Anyway, I wouldn't worry too much about SSD performance right now. Even a degraded SSD still outperforms a hard drive in read and large-file write tasks. It tends to be the small, random write tests that slow down quite a bit, and even that usually takes months or even a year or two to be noticeable. You can "recondition" an SSD using third party software, and there are routines for clearing a drive and restoring it. Hopefully, though, Apple adds TRIM support to OS X 10.7. In the meantime, the Toshiba controller in the new Airs does do some "garbage collection" intended to maintain higher performance for a longer period of time.
     
  4. JesseW6889 thread starter macrumors 6502

    Joined:
    Dec 12, 2010
    #4
    Just to be sure I understand... reconditioning a SSD will return it to its original speed?

    So, I could use my MBA, and as I use the SSD for temp files it will at some point become 'full' of deleted data (so that there exists no 'clean' cells to be written to) and it would be at this point that I would experience some degradation of performance based on the read/remove/rewrite cycle or whatever it is that trim is supposed to prevent. So that I'd basically have a 128gb with 60 gigs of storage used, and the rest 'dirty'. Could i just 'recondition' the drive, then restore the 60 gigs of 'used' data, so long as im not doing a sector by sector exact replica restore? Will that leave me with a 'brand new' SSD?

    Or does OSX not suffer from this problem anyways, or if it does, MIGHT it be fixed by .7 (before it even becomes an issue for me?)
     
  5. KPOM macrumors G5

    Joined:
    Oct 23, 2010
    #5
    There's some debate about the effectiveness of reconditioning. There are a limited number of writes on any flash module, and reconditioning might not restore all the original write speeds.

    Basically, the issue with SSDs is that flash memory can only be rewritten to if it is fully cleared. Unlike a magnetic drive, the controller can't simply overwrite existing data. Thus, if a drive has been written to over and over again, a lot of "available" sectors will actually have some old data on it and will need to be cleared before they can be rewritten to. That slows things down. TRIM and "garbage collection" are ways of clearing out old data in the background (when the computer isn't busy), saving time later on.

    Unfortunately, clearing out an SSD isn't as simple as formatting it or overwriting old data with 0s (such as what is often done with magnetic hard drives). There are special commands in Linux to do this as part of a complete format, and TRIM does this to some extent. What the "reconditioning" utilities for the Mac do is attempt to replicate some of these routines.

    I'm not an engineer, so I'm sure I missed some technical points.
     

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