Hello All,
Summary:
~~~~~~~~
cp command for mirrored zfs hung when all the disks in the mirrored
pool were unavailable.
Detailed description:
~~~~~~~~~~~~~~~~~~~~~
The cp command (copy a 1GB file from nfs to zfs) hung when all the disks
in the mirrored pool (both c1t0d9 and c2t0d9) were removed physically.
NAME STATE READ WRITE CKSUM
test ONLINE 0 0 0
mirror ONLINE 0 0 0
c1t0d9 ONLINE 0 0 0
c2t0d9 ONLINE 0 0 0
We think if all the disks in the pool are unavailable, cp command should
fail with error (not cause hang).
Our request:
~~~~~~~~~~~~
Please investigate the root cause of this issue.
How to reproduce:
~~~~~~~~~~~~~~~~~
1. create a zfs mirrored pool
2. execute cp command from somewhere to the zfs mirrored pool.
3. remove the both of disks physically during cp command working
= hang happen (cp command never return and we can't kill cp command)
One engineer pointed me to this page
http://opensolaris.org/os/community/arc/caselog/2007/567/onepager/ and
indicated that if all the mirrors are removed zfs enters a hang like
state to prevent the kernel from going into a panic mode and this type
of feature would be an RFE.
My questions are
Are there any documentation of the "mirror" configuration of zfs that
explains what happens when the underlying
drivers detect problems in one of the mirror devices?
It seems that the traditional views of "mirror" or "raid-2" would expect
that the
mirror would be able to proceed without interruption and that does not
seem to be this case in ZFS.
What is the purpose of the mirror, in zfs? Is it more like an instant
backup? If so, what can the user do to recover, when there is an
IO error on one of the devices?
Appreciate any pointers and help,
Thanks and regards,
Karthik
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