Date: Sun, 5 Nov 2000 17:43:55 +1100 From: Greg Lehey <grog@lemis.com> To: Gabor Kincses <gabor@acm.org> Cc: randy@psg.com, FreeBSD Questions <questions@FreeBSD.ORG> Subject: Re: CCD Message-ID: <20001105174355.V307@sydney.worldwide.lemis.com> In-Reply-To: <3A038A39.D646F2F2@acm.org>; from gabor@acm.org on Fri, Nov 03, 2000 at 10:02:01PM -0600 References: <3A038A39.D646F2F2@acm.org>
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[moved to -questions; this has nothing to do with SCSI] On Friday, 3 November 2000 at 22:02:01 -0600, Gabor Kincses wrote: > Hello, > > This is all I had to do: Is this a reply to something? > KERNEL config file: > pseudo-device ccd 4 # Concatenated disk driver > > gabor@steinbeck: <1160> cat /etc/ccd.conf > ccd0 512 0 /dev/ad0s3f /dev/ad2s1f > > I have been using this since June. Early on I measured performance and > I got ~75% increased random read and sequential block read/write per > bonnie. bonnie suffers from file system caching but I ran it with 2x > the size of my ram, which should eliminate caching artifacts. No, it just reduces them. Use rawio to eliminate them. > BTW, the two disks are quite dissimilar (13 and 4 GB), I just made > sure to create identical sized `f' partitions. Since performance > speaks for itself, I consider the disk geometry a non-issue. If you don't mind losing 9 GB of storage space. I'd call that an issue. You'd probably be better off concatenating. > Granted I had to increase the interleave factor to much bigger than > what the man page recommended to get optimum performance. Yes, the man page is wrong. What stripe size did you use? You don't want a power of 2 as an interleave factor; that will leave all superblocks on one drive, at least for 2 disks. > You may also want to strip swap like this (/etc/fstab): > > /dev/ad0s2b none swap sw 0 0 > /dev/ad2s1b none swap sw 0 0 I'm not sure what you're saying here. > I may have had to fiddle with disklabel when installing, but it > wasn't a big deal, I think I just followed ccdconfig(8). > > BTW, does anybody have numbers on IDE disk speeds to help decide if a > third disk would max-out a 33MHz UDMA IDE controller? You can't put a third disk on an IDE controller. But even the second one will give you serious performance hits, since the transfers are serialized. It's been a while since I've compared ccd and Vinum performance. Vinum used to be much better, but some problems in ccd have been fixed. You get many other advantages from Vinum. Greg -- Finger grog@lemis.com for PGP public key See complete headers for address and phone numbers To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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