Date: Tue, 23 Jul 1996 19:50:32 -0400 (EDT) From: Matthew Jason White <mwhite+@CMU.EDU> To: freebsd-questions@freefall.FreeBSD.org, Justin Ashworth <ashworth@fubar.cs.montana.edu> Subject: Re: Disk Striping Message-ID: <slxKJ8O00YUp0oZYA0@andrew.cmu.edu> In-Reply-To: <Pine.OSF.3.91.960723171623.25748A-100000@fubar.cs.montana.edu> References: <Pine.OSF.3.91.960723171623.25748A-100000@fubar.cs.montana.edu>
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Excerpts from internet.computing.freebsd-questions: 23-Jul-96 Disk Striping by Justin Ashworth@fubar.cs > Does anybody know of limitations that would be imposed under FreeBSD by > striping a 1GB Western Digital Caviar drive with a 2GB Seagate Baraccuda? > Would there be any problems with the striping and the multiple slices that > FreeBSD creates? Oh yeah, the Western Digital is IDE and the Seagate is > SCSI...that probably ruins my chances right there, doesn't it? Well, the situation is obviously less than ideal. To be honest, I've never tried the striping driver on an IDE drive, but it *should* work. The ccd driver uses FreeBSD disk components (files) to do the striping. In other words, you don't stripe a disk, you stripe a slice on a disk. As for the desparate disk sizes, the default CCD behaviour is to stripe the components equally until the smallest disk is full and then continue using the remaining disks. In your case, this means that CCD would stripe the first GB and then write sequentially to the larger disk. If you specify the CCDF_UNIFORM flag, then CCD will report the disk full as soon as the smallest component is full. You can probably get around this by partitioning the SCSI disk and then specifying two 1GB SCSI partitions to be sliced. This means that twice as many disk operations will go to the 'cuda as to the IDE disk, but the Seagate is a fast disk, so this may be acceptable given the circumstances. I think the best suggestion may be to back your system up and then play with it and see what you can make it do. I'll be happy to help as I'm able. -Matt
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