Date: Fri, 05 Nov 1999 00:26:14 +0100 From: Mattias Pantzare <pantzer@ludd.luth.se> To: Greg Lehey <grog@lemis.com> Cc: freebsd-fs@FreeBSD.ORG Subject: Re: feature list journalled fs Message-ID: <199911042326.AAA02859@zed.ludd.luth.se> In-Reply-To: Message from Greg Lehey <grog@mojave.sitaranetworks.com> of "Thu, 04 Nov 1999 16:13:17 EST." <19991104161317.49512@mojave.sitaranetworks.com>
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> On Thursday, 4 November 1999 at 1:20:36 +0100, Mattias Pantzare wrote: > >> I am under the impression that you can only enlarge a vinum volume if it > >> in a RAID 0 configuration (concatenation). Obviously, it would be very > >> difficult to enlarge a RAID 1 or RAID 5 configuration as it would require > >> restriping the data across all disks; I'm not familiar with any product, > >> hardware or software, that can do this. > > > > 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. Disk, not stripe. > > > I think that it is a strange mix of RAID 5 and concatenation. All > > data is still parity protected. It might not be as fast as a true > > RAID 5, but it can be very usful. > > What's the difference? If you have 3 disks and 3 stripes and number sectors from 1 to 6: Disk 1 Disk 2 Disk 3 1 2 P P 3 4 5 P 6 Then add a new disk: Disk 1 Disk 2 Disk 3 New Disk 1 2 P 7 P 3 4 8 5 P 6 9 All you have to do is recalculate the new parity data when you write new data if you zero the new disk before using it. Disk accesses will not be spread out as in normal RAID5, but you still get parity protection. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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