On Tuesday, 11 December 2001 at 23:41:51 +0100, Wilko Bulte wrote: > On Wed, Dec 12, 2001 at 09:00:34AM +1030, Greg Lehey wrote: >> On Tuesday, 11 December 2001 at 15:34:37 +0100, Wilko Bulte wrote: >>> On Tue, Dec 11, 2001 at 11:06:33AM +1030, Greg Lehey wrote: >>>> On Monday, 10 December 2001 at 10:30:04 -0800, Matthew Dillon wrote: >>>>> > > .. > >>>>> and will go down the drain for reads if you cross a stripe - >>>>> something that is quite common I think. >>>> >>>> I think this is what Mike was referring to when talking about parity >>>> calculation. In any case, going across a stripe boundary is not a >>>> good idea, though of course it can't be avoided. That's one of the >>>> arguments for large stripes. >>> >>> In a former life I was involved with a HB striping product for SysVr2 >>> that had a slightly modified filesystem that 'knew' when it was >>> working on a striped disk. And as it know, it avoided posting I/O s >>> that crossed stripes. >> >> So what did it do with user requests which crossed stripes? > > Memory is dim, but I think the fs code created a second i/o to the > driver layer. So the fs never sent out an i/o that the driver layer had > to break up.
That's what Vinum does. > In case of a pre-fetch while reading I think the f/s would just > pre-fetch until the stripe border and not bother sending out a > second i/o down. Yes, that's reasonable. > In the end all of this benchmarked quite favorably. Note that this > was 386/486 era, with the classic SysV filesystem. I don't think that UFS would behave that differently, just faster :-) Greg -- See complete headers for address and phone numbers To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
