Jeff -
That sounds like a great idea...
Another idea might to be have a zpool create announce the 'availability'
of any given configuration, and output the Single points of failure.
# zpool create mypool a b c
NOTICE: This pool has no redundancy.
Without hardware redundancy (raid1 / 5),
a single disk failure will destroy the whole pool.
# zpool create mypool raidz a b c
NOTICE: This pool has single disk redundancy.
Without hardware redundancy (raid1 / 5),
this pool can survive at most 1 disks failing.
# zpool create mypool raidz2 a b c
NOTICE: This pool has double disk redundancy.
Without hardware redundancy (raid1 / 5),
this pool can survive at most 2 disks failing.
It would be especially nice if it was able to detect silly
configurations too (like adding dimple disks to a raidz or something
like that (if it's even possible) and announce the reduction in
reliability.
Thoughts? :)
Nathan.
On Mon, 2006-07-17 at 18:35, Jeff Bonwick wrote:
> > I have a 10 disk raidz pool running Solaris 10 U2, and after a reboot
> > the whole pool became unavailable after apparently loosing a diskdrive.
> > [...]
> > NAME STATE READ WRITE CKSUM
> > data UNAVAIL 0 0 0 insufficient replicas
> > c1t0d0 ONLINE 0 0 0
> > [...]
> > c1t4d0 UNAVAIL 0 0 0 cannot open
> > --------------
> >
> > The problem as I see it is that the pool should be able to handle
> > 1 disk error, no?
>
> If it were a raidz pool, that would be correct. But according to
> zpool status, it's just a collection of disks with no replication.
> Specifically, compare these two commands:
>
> (1) zpool create data A B C
>
> (2) zpool create data raidz A B C
>
> Assume each disk has 500G capacity.
>
> The first command will create an unreplicated pool with 1.5T capacity.
> The second will create a single-parity RAID-Z pool with 1.0T capacity.
>
> My guess is that you intended the latter, but actually typed the former,
> perhaps assuming that RAID-Z was always present. If so, I apologize for
> not making this clearer. If you have any suggestions for how we could
> improve the zpool(1M) command or documentation, please let me know.
>
> One option -- I confess up front that I don't really like it -- would be
> to make 'unreplicated' an explicit replication type (in addition to
> mirror and raidz), so that you couldn't get it by accident:
>
> zpool create data unreplicated A B C
>
> The extra typing would be annoying, but would make it almost impossible
> to get the wrong behavior by accident.
>
> Jeff
>
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