Re: Boot from ZFS

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.

> I guess what I'm trying to say is, that you can still lose everything on an 
> entire pool, so backups are still essential, an a couple of smaller pools is 
> probably preferable to one big pool (restore time is less).  zfs is not %100 
> (yet?).  The lack of any type of fsck still causes me concern.

Regardless of the technology, backups are essential.  If you actually value
your data, off-site backups are essential.

-- Brooks

> Duncan
> 
> PS I do think zfs is great, but it's not perfect.  If I can boot directly off 
> zfs, I would make sure I had an offline replication of the boot disk, in case 
> of failure.
> 
> On Sat, 12 Jul 2008 04:24:30 am Ollivier Robert wrote:
> > According to Steve Bertrand:
> > > "In the latest code, it's possible to boot directly from ZFS, no longer
> > > requiring a small non-ZFS boot partition. "No you can use only ZFS and
> > > just enjoy it," he stated."
> > >
> > > ...if not, where can I find information on the best procedure to do so?
> >
> > This code is not yet committed to CURRENT, it is currently in a P4 branch.
> > Doug Rabson is also doing some work on it according to p4 changes.
> 
> 
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