Date: Sat, 12 Jul 2008 11:29:17 -0400 From: Steve Bertrand <steve@ibctech.ca> To: Brooks Davis <brooks@freebsd.org> Cc: Duncan Young <duncan.young@pobox.com>, freebsd-current@freebsd.org Subject: Re: Boot from ZFS Message-ID: <4878CDCD.5060700@ibctech.ca> In-Reply-To: <20080712045508.GA28756@lor.one-eyed-alien.net> References: <4877A343.2010602@ibctech.ca> <20080711182430.GA76378@keltia.freenix.fr> <200807121043.10473.duncan.young@pobox.com> <20080712045508.GA28756@lor.one-eyed-alien.net>
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Brooks Davis wrote: > On Sat, Jul 12, 2008 at 10:43:09AM +1000, Duncan Young wrote: >> Be carefull, I've just had a 6 disk raidz array die. Complete failure which >> required restore from backup (the controler card which had access to 4 of the >> disks, lost one disk, then a second (at which point the machine paniced, Upon >> reboot the raidz array was useless (Metadata corrupted)). I'm also getting >> reasonably frequent machine lockups (panics) in the zfs code. I'm going to >> start collecting crash dumps see if anyone can help in the next week or two. > > If you look at the research on disk corruption and failure modes both > in recent proceeding of FAST and the latest issue of ;LOGIN: it's clear > that any RAID-like scheme that does not tolerate double faults is likely > to fail. In theory, zfs should tolerate certain classes of faults > better than some other technologies, but can't deal with full disk > double faults unless you use raidz2. Going back to my initial question (ie: subject), I've implemented the box in such a way that I boot via USB disk that contains only the /boot partition. This allows me to use all four entire disks in my ZFS pool instead of creating a UFS slice on one of them first. It then mounts / via ZFS and the system takes over from there. This box IS a backup box...in the sense of convenience. We still have off-site backup, this is just for quick retrieval of information if the need arises. If this box fails, We build a new one. That said, I did use raidz and sacrificed the equivalent of one drive. I did some testing (pop out a drive, reboot, etc) and it works very well. I do like the raidz2 idea, and when my needs justify adding more disks, I'll double the space and use the double protection. > Regardless of the technology, backups are essential. If you actually value > your data, off-site backups are essential. I fully agree with this statement. I've also been a long time believer that a backup is only as good as the time and difficulty level it takes to restore from it. Steve
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