Date: Fri, 13 Nov 1998 14:06:39 +1100 From: Peter Jeremy <peter.jeremy@auss2.alcatel.com.au> To: hackers@FreeBSD.ORG Subject: Re: [Vinum] Stupid benchmark: newfsstone Message-ID: <98Nov13.140613est.40335@border.alcanet.com.au>
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Greg Lehey <grog@lemis.com> wrote: > And it's almost impossible to find >spindle synchronized disks nowadays. Seagate Barracuda's support it, I assumed that the newer Seagates did as well. The impression I got was that all you had to do was wire the `spindle sync' lines from all the disks together and then designate all except one as a sync'd slave. Admittedly, I've never tried actually using it. > Finally, aggregating involves a >scatter/gather approach which, unless I've missed something, is not >supported at a hardware level. Each request to the driver specifies >one buffer for the transfer, so the scatter gather would have to be >done by allocating more memory and performing the transfer there (for >a read) and then copying to the correct place. Since the actual data transfer occurs to physical memory, whilst the kernel buffers are in VM, this should just require some imaginative juggling of the PTE's so the physical pages (or actual scatter/gather requests) are de-interleaved (to match the data on each spindle). This does assume that the actual stripe is a multiple of the pagesize (if scatter/gather isn't supported). And I'm not saying that implementing this would be easy or clean. What would be useful is some help (from vinum or ccd) to ensure that the cylinder group blocks (superblock + inode maps etc) don't cross stripes. Peter -- Peter Jeremy (VK2PJ) peter.jeremy@alcatel.com.au Alcatel Australia Limited 41 Mandible St Phone: +61 2 9690 5019 ALEXANDRIA NSW 2015 Fax: +61 2 9690 5247 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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