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Jared
Asked: 2009-05-02 06:17:10 +0800 CST

HCSD write cycles?

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I would like to run the Sheevaplug as a basic home server. I plan on storing all my data on a 32 gig HCSD card while running the OS off the built in flash. I will be doing things such as running a basic webserver, downloading torrents, and using bashpod to download podcasts with a cron job. Will HCSD cards be able to handle this, or will there write cycle limit get hit quickly and kill the card?

sd-card

2 Answers

  1. The question is a difficult one because most good flash cards practice wear leveling, so it's not easy to estimate.

    You can count on at least 100k writes for a standard flash memory card.

    With good wear leveling, though, you can expect to write up to 100k * card capacity.

    For instance, with a 32GB card with aggressive wear leveling, you can expect to write 3,200,000GB of data to the card before it starts hitting the 100k write maximum for a given memory cell.

    In practice it's much lower, because a single byte write will cause a flash block write, which hits between 4k and 64k in a single flash block.

    Further, even good cards don't have theoretically optimal wear leveling - they all make compromises in one way or another.

    So it'll depend on your exact usage pattern.

    But few people will actually hit that limit in normal, or even slightly above normal, usage in 1-2 years, so as long as you replace the card every year or two you should never see a problem unless you're writing a few GB per day.

    -Adam

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  2. Dan's got a nice writeup about this kind of thing:

    http://www.dansdata.com/flashswap.htm

    but I think it really just boils down to how often you write to the device, keeping in mind that "often" to us isn't really "often" to a computer. The netbook guys are all over this stuff, too:

    http://www.notebookreview.com/default.asp?newsID=4258

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