Date: Thu, 15 Nov 2007 16:14:15 +0100 (CET) From: Oliver Fromme <olli@lurza.secnetix.de> To: freebsd-current@FreeBSD.ORG, arne_woerner@yahoo.com, bsd@fluffles.net Subject: Re: geom_raid5 inclusion in HEAD? Message-ID: <200711151514.lAFFEFFs072976@lurza.secnetix.de> In-Reply-To: <165798.11850.qm@web30314.mail.mud.yahoo.com>
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Arne Wörner wrote: > Oliver Fromme wrote: > > Just a small question: I noticed that the new gvinum > > raid5 implementation (in P4) allows adding disks to an > > existing RAID5, even while it is running. Does geom_raid5 > > support that, too? (ZFS doesn't, unfortunately.) > > Nope... graid5 doesnt do such things... I found no way, that could do it > without hurting the disks too much (I was afraid, that a power failure could > destroy the necessary knowledge about the size of the new-config-area; and I > didnt know how to do the beginning: it seemed like the first few blocks need a > special treatment, because there the new-config-area and the old-config-area > overlap)... OK. I don't know the inner workings of geom_raid5, so I can't tell how difficult it would be to implement there. Here's a little description and some ASCII graphics that explin how growing RAID5 was implemented in the new gvinum: http://lists.freebsd.org/pipermail/p4-projects/2007-July/020082.html > But Veronica is developing a tool, that can do it in offline mode... With > service interruption... > > But growfs induces a service interruption anyway and it is buggy, if u do > not zero the new area... Veronica filed a bug report about this... Hm. I used growfs only once, and it worked fine. Was there a regression introduced at some point? It should certainly be fixed, because growfs seem to be very useful. About service interruption: growfs only takes a few seconds, which might be acceptable in most cases. But taking a whole RAID5 down to add disks and then rebuilding it takes a _lot_ longer. Therefore I think the feature to add disks to a live RAID5 would be very valuable. > Nowadays it is common practice to have 2 ot more hosts, that can substitute > each other (hot-standby or how they call it today), so that it doesnt matter, > if a box is damaged or in maintenance mode or... isnt it? It depends. Building a fail-over cluster with FreeBSD is not trivial if you need a synchronized, consistent and reliable file system on all of the nodes. Of course you can use third-party black boxes such as a cluster of NetApp Filers or whatever. That would work (I've put such setups into production myself), but it costs a non-negligible amount of money, and it's certainly not suitable for everyone. YMMV, of course. Best regards Oliver -- Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing b. M. Handelsregister: Registergericht Muenchen, HRA 74606, Geschäftsfuehrung: secnetix Verwaltungsgesellsch. mbH, Handelsregister: Registergericht Mün- chen, HRB 125758, Geschäftsführer: Maik Bachmann, Olaf Erb, Ralf Gebhart FreeBSD-Dienstleistungen, -Produkte und mehr: http://www.secnetix.de/bsd One Unix to rule them all, One Resolver to find them, One IP to bring them all and in the zone to bind them.
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