Date: Thu, 4 Nov 1999 16:26:58 -0500 (EST) From: Kelly Yancey <kbyanc@posi.net> To: Greg Lehey <grog@lemis.com> Cc: Mattias Pantzare <pantzer@ludd.luth.se>, freebsd-fs@FreeBSD.ORG Subject: Re: feature list journalled fs Message-ID: <Pine.BSF.4.05.9911041617350.19301-100000@kronos.alcnet.com> In-Reply-To: <19991104161317.49512@mojave.sitaranetworks.com>
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> > Solaris DiskSuite almost extends RAID 5 configruations. You can add disks to a > > RAID 5 set, but the extra disks will only hold data, no parity. > > That's normal for RAID-5. Only one disk in any stripe contains the > parity information. > > Greg Except that, if I understand correctly, the new disks don't have parity for them stored anywhere. They aren't really in on the RAID 5 game, but tag along and just pretend to be. All this talk about extending RAID 5 plexes has got be thinking about the oft-overlooked RAID 4. I realize this isn't currently implemented in vinum, but I understand it has similar (although slightly different, not worse, just different) performance characteristics to RAID 5. But I would think that RAID 4 would be much simpler to extend because of the fact only 1 disk contains the parity; rather than restriping, one only needs to recalculate parity. But then again, RAID 4 is one of the black sheep of the RAID family :) Kelly -- Kelly Yancey - kbyanc@posi.net - Richmond, VA Director of Technical Services, ALC Communications http://www.alcnet.com/ Maintainer, BSD Driver Database http://www.posi.net/freebsd/drivers/ Coordinator, Team FreeBSD http://www.posi.net/freebsd/Team-FreeBSD/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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