[email protected] writes: > if you really need fast writes you need battery backed ram. if you don't > need very much (up to a couple of gigs with the writes being converted > from many small writes to a few large writes by the hardware) you can use > a raid card/chassis with it. if you need a lot you can look at something > like ACard's ANS-9010 Serial ATA RAM disk ( > http://techreport.com/articles.x/16255 ), it's as much faster than a X25E > as an X25E is from a normal hard drive.
I was actually researching this recently, see, I want to give my VPS customers a small partition they can use for an external ext3 journal. (my understanding is that if you set ext3 to 'full journaling' mode, it writes all data to the journal, making it the place to put a write cache) Even if it's less than the amount of ram I have in the box, 512M of write cache for every 1GiB ram you rent would, I think, make disk performance compellingly better. The ACARD solution would have sold me, save for one problem; it doesn't support ECC ram, and using a linux Dom0, I can't come up with a way to protect myself from flipped bits. A mirror of the thing won't help, either, as a single flipped bit won't return a read error (and therefore the mirror won't know which value is good. a mirror, then doing a nightly resync and checking for differences is the only way I can think of even detecting flipped bits.) I'm wondering about the X25-e. I hear they don't fail often, but is their 'silent corruption' and 'bad sector' error rate better/worse than physical disks? Bad sectors can be fixed by a mirror (which makes it a little expensive right now.) Silent corruption can not. (not without block checksums or other features that stable linux volume managers lack right now.) The X25-e would also give me a reasonable amount of space. with 64G storage, I could give each customer (almost) 2x the ram they get in ssd space, which for the larger customers means they could run entirely off ssd, only hitting sata when they need bulk storage. Problem is cost. And I'm not really the type to use unmirrored storage without strong evidence it's safe, compounding the cost issue. _______________________________________________ Discuss mailing list [email protected] http://lopsa.org/cgi-bin/mailman/listinfo/discuss This list provided by the League of Professional System Administrators http://lopsa.org/
