Messages in this thread | | | From | (bill davidsen) | Subject | Re: raid0 slower than devices it is assembled of? | Date | 17 Dec 2003 21:55:40 GMT |
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In article <Pine.LNX.4.58.0312170758220.8541@home.osdl.org>, Linus Torvalds <torvalds@osdl.org> wrote: | | | On Wed, 17 Dec 2003, Peter Zaitsev wrote: | > | > I'm pretty curious about this argument, | > | > Practically as RAID5 uses XOR for checksum computation you do not have | > to read the whole stripe to recompute the checksum. | | Ahh, good point. Ignore my argument - large stripes should work well. Mea | culpa, I forgot how simple the parity thing is, and that it is "local". | | However, since seeking will be limited by the checksum drive anyway (for | writing), the advantages of large stripes in trying to keep the disks | independent aren't as one-sided.
There is no "the" parity drive, remember the RAID-5 parity is distributed. A write takes two seeks, a read, a data write, and a parity write, but the parity isn't a bottleneck, and as noted above the size only need be the blocks containing the modified data. -- bill davidsen <davidsen@tmr.com> CTO, TMR Associates, Inc Doing interesting things with little computers since 1979. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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