On Monday, 28 January 2002 at 18:34:10 +0100, Bernd Walter wrote: > On Mon, Jan 28, 2002 at 09:49:59AM -0500, Jason Andresen wrote: >> I'm hoping there is an easy answer to this one... >> >> Is there some way vinum can be tickled such that it writes to all disks >> in a plex at once? For instance, say I have a 6 disk RAID5 array >> that I'm writing a 200MB file to. Is there some way I can make >> vinum attempt to write data to all of the drive simultaniously? > > You can't easily increase performance in a single file access case > with more disks. Especialy in the R5 case where you have several > blocks depend on the same parity.
Well, in fact it's particularly interesting in the RAID-5 case: then you can write an entire band without having to read first, thus doubling the throughput. The problem with this approach is that FreeBSD is currently limited to an I/O size of 128 kB. A reasonable stripe size for RAID-5 is 300 kB or so, so in Jason's example you'd have to be able to issue an I/O request of 1.5 MB. Until this is possible, there's no point in writing the code (which would be possible, though not trivial). >> If vinum already does that I'm probably just saturating the PCI bus >> and there's nothing more I can do, but it seems like I should have >> a tougher time saturating the bus with 5400RPM drives... > > Vinum is designed for multiple file access which is a more common > situation for a unix system. Well, it tries to be universally useful. But this particular optimization doesn't currently make sense. Greg -- See complete headers for address and phone numbers To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message
