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Thread: Scratch disks?

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    Scratch disks?

    Sorry, title should read scratch disks.

    Guys; got a 60gb solid state (with around 8gb free) and 2x 2tb drives about 30% capacity used.

    Bridge and PS have been complaining of late and i'm wondering what best scratch disk config would be?

    Any takers please?

    Eric
    Last edited by ericimbs; 19-07-2011 at 8:50pm.

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    thanks guys. got it sorted. no need for response.

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    Administrator ricktas's Avatar
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    Your scratch disk should not be the same disk as where photoshop is installed. Also SSD disks are not the best place to do all your reading/writting. They work best for installing operating systems and primarily used software, but store your photos etc elsewhere.

    People seem to be under the misconception that a Solid State Drive, due to have no moving parts, is going to last a lifetime. Where evidence is already emerging of them failing. I have most of my programmes on my SSD, but my photos are stored on a HDD.

    Some information I had from another site I visit:

    * Flash memory chips have a property where they 'wear out' as you write to them. Only writing wears them out, not reading. And each individual memory cell has a certain predicted number of writes it can take before dying. By estimates, MLC should last about 100,000 write cycles; SLC about 1,000,000. Because it would be possible that you could try to use a drive such that it writes 1 MB, erases it, then writes that 1 MB again; SSDs have "wear leveling" algorithms where they won't actually write the second request to the same physical cells. They will effectively use up the entire drive's worth of cells before they re-write a single one. So you would have to re-write that 1 MB say, 64 thousand times before you even get to the SECOND write pass on a 64 GB drive. (128 thousand times on a 128 GB drive, etc.)

    Most SSDs also have more capacity of chips than they claim (For Intel's SSDs, it's about 25% more, I don't know about other manufacturers,) so even when the cells start to wear out; there are 'spares' to take their place for a while. (spinning magnetic hard drives also do this.) What this amounts to is that it takes a *LOT* of writes to wear out an SSD. For that 128 GB SSD, if you were to be able to write to it at 50 MB/s (a good estimate for most 128 GB SSDs out there,) continuously, it would take 42.6 minutes to completely fill. If it's the worse MLC drive, that comes to about 8 years of continuous write/erase/write to hit the 100,000 writes mark.

    For a faster SLC, you can write 3x faster, but you have 10x as many cycles, so it comes out to about 30 years. Of nonstop writing.

    Any reading is "free". If you write to it once, then read continuously, it should work "forever" (within the confines of reality, obviously.)


    For the above reasons you should never de-fragment an SSD.
    Last edited by ricktas; 29-07-2011 at 8:15am.
    "It is one thing to make a picture of what a person looks like, it is another thing to make a portrait of who they are" - Paul Caponigro

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    Administrator ricktas's Avatar
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    PS, I fixed your thread title.

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