Date: Wed, 4 Nov 1998 10:13:07 -0500 (EST) From: Steve Ames <steve@ns1.cioe.com> To: grog@lemis.com, steve@inc.net, steve@ns1.cioe.com Cc: freebsd-isp@FreeBSD.ORG Subject: Re: Vinum on root partition (was: disk mirroring?) Message-ID: <199811041513.KAA06958@ns1.cioe.com> In-Reply-To: <19981104150946.L784@freebie.lemis.com>
next in thread | previous in thread | raw e-mail | index | archive | help
> Ah, you're thinking in terms of ccd, where everything crashes if one > drive goes down (thus lowering uptime instead of increasing it). If > you lose one plex with Vinum, the others are unaffected. Here's a > case from my test machine: > > vinum -> l -r obj > V obj State: up Plexes: 2 Size: 400 MB > P obj.p0 C State: up Subdisks: 2 Size: 400 MB > P obj.p1 S State: down Subdisks: 4 Size: 400 MB > S obj.p0.s0 State: up PO: 0 B Size: 200 MB > S obj.p0.s1 State: up PO: 200 MB Size: 200 MB > S obj.p1.s0 State: up PO: 0 B Size: 100 MB > S obj.p1.s1 State: up PO: 100 MB Size: 100 MB > S obj.p1.s2 State: up PO: 200 MB Size: 100 MB > S obj.p1.s3 State: up PO: 300 MB Size: 100 MB I have things setup to stripe and thats what confused me. In my mind if I take 2 200M partitions and stripe across them I should end up with 1 200M plex (the other 200M being completely a mirror state). I can't have 400M because then if 1 drive goes bad I'm out half my data right? In your above example you have a striped plex with 4 subdisks. Each subdisk is 100M. The total capacity of the plex is 400M. If I write 400M of data to that and lose a subdisk don't I lose data? How is a "mirroring" setup configured? > > Then there the issue of no 'root' partition support. > > You said. > > Would you be interested if I implemented partition encapsulation? > Basically, that would be a subdisk which is not part of a Vinum drive, > so you could point to an existing disk partition. This would enable > you to mirror in the way you planned, and would also make it easier to > support root partitions. Ah. Sweetness. If I understand you correctly here that would be most excellent. Obviously you'd lose the striping efficiencies here since one of the subdisks ins't part of the vinum drive, but that would let you mirror things in a very simple manner and then support dual writes. You could probably also still read from the most unused drive while writing to both, this would give _some_ efficiencies. -Steve To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-isp" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199811041513.KAA06958>