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Thread: Drive capacity with Sandforce compression

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    Drive capacity with Sandforce compression

    My understanding is that the Sandforce SSD controller compresses data on the fly to reduce the amount of information written to the flash memory and that this is primarily to increase the longevity of the drive.

    Is the side effect of this that I would have more space? Basically how much space does a 'compressed' windows 7 installation use compared with a non-Sandforce SSD drive.

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    Re: Drive capacity with Sandforce compression

    As I understand it the controller on the V2-E reserves 13% of capacity for 'overprovisioning' - as you said, to prolong the life of the drive. So, in the case of the 60gb drive total capacity is 64gb, SF reserves 4gb of this even before Windows formats it, leaving you with 55.7gb after formatting.

    I don't really know how much space the controller compresses the Windows installation into - would have thought it packs it quite tight as most of it would be highly compressible data - and I don't think there's any way of actually monitoring the compression levels (perhaps if they ever release the toolbox in some working form for these drives it might have some form of meter, but I suspect not).

    The thing is, the controller will only report the 'normal' and not the compressed space allocation, so, for example, my Win7 installation shows as 15gb even though it's probably sqeezed into a much smaller space. Upshot is, you won't get any extra space to play with as such, any gains are reserved by the drive for its own use. Fiendish, isn't it?

    There's a good article on Anandtech (although it's about the Agility2, the principle is the same):

    http://www.anandtech.com/show/3690/t...ormance-loss/1
    Last edited by marktime; 18-08-2010 at 07:33 AM.

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    Re: Drive capacity with Sandforce compression

    Quote Originally Posted by marktime View Post
    As I understand it the controller on the V2-E reserves 13% of capacity for 'overprovisioning' - as you said, to prolong the life of the drive. So, in the case of the 60gb drive total capacity is 64gb, SF reserves 4gb of this even before Windows formats it, leaving you with 55.7gb after formatting.
    This is something I had assumed, but didn't know for sure. When SSDs first appeared they were all multiples of 8GB, where as now they are rounded down, so we have 40GB, 60GB, 80GB etc.

    Personally I prefer this approach. I would rather have a slightly smaller capacity to start with, safe in the knowledge that bad cells will not erode this total and will instead come out of that pool.

    On the compression aspect of Sandforce; If the processing in the controller is fast enough, compressing the data being written and read from the drive will increase the overall throughput of the drive. Providing the flash chips are the bottleneck that is.

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