Discussion:
pool/dataset disappeared?
(too old to reply)
Durval Menezes
2012-06-14 23:50:12 UTC
Permalink
Hello Folks,

I have an old machine here running RHEL4 with kernel 2.6.27.57 downloaded
from kernel.org, compiled and installed manually. It also has zfs-fuse
0.5.0 with a single partition on its hard disk dedicated for zfs use
(/dev/sda6), via the creation of a single pool called "testpool"; this
configuration has been working great since 2008 or so.

Yesterday, the machine was inadvertently powered off without a proper
shutdown, and when powered back on, the pool simply refuses to mount:

# zfs mount testpool
cannot open 'testpool': dataset does not exist

# zfs list
no datasets available

Can anyone offer any help on how to recover from this? I've searched both
this list and the Web at large, but failed to find anything really related
to my situation.

Thanks in advance,
--
Durval Menezes.
--
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Björn Kahl
2012-06-15 00:04:49 UTC
Permalink
Hello Durval Menezes,
Post by Durval Menezes
Hello Folks,
I have an old machine here running RHEL4 with kernel 2.6.27.57
downloaded from kernel.org, compiled and installed manually. It also
has zfs-fuse 0.5.0 with a single partition on its hard disk dedicated
for zfs use (/dev/sda6), via the creation of a single pool called
"testpool"; this configuration has been working great since 2008 or
so.
Pretty old. :-)
Post by Durval Menezes
Yesterday, the machine was inadvertently powered off without a proper
# zfs mount testpool
cannot open 'testpool': dataset does not exist
# zfs list
no datasets available
Can anyone offer any help on how to recover from this? I've searched
both this list and the Web at large, but failed to find anything
really related to my situation.
Not enough data.


Is the disk still there?

Has it possibly been renamed by the kernel? I.e. is /dev/sda6 still
named sda6 after the latest reboot?

Anything interesting in the logs?

What says zpool status -v?

What says zpool import?


Best regards

Björn
--
| Bjoern Kahl +++ Siegburg +++ Germany |
| "googlelogin@-my-domain-" +++ www.bjoern-kahl.de |
| Languages: German, English, Ancient Latin (a bit :-)) |
Durval Menezes
2012-06-15 00:24:03 UTC
Permalink
Hi Bjorn,
Post by Björn Kahl
Hello Durval Menezes,
Post by Durval Menezes
Hello Folks,
I have an old machine here running RHEL4 with kernel 2.6.27.57
downloaded from kernel.org, compiled and installed manually. It also
has zfs-fuse 0.5.0 with a single partition on its hard disk dedicated
for zfs use (/dev/sda6), via the creation of a single pool called
"testpool"; this configuration has been working great since 2008 or
so.
Pretty old. :-)
No doubt. But if it isn't broken, why fix it? ;-) This is the first hiccup
this machine has given me in all those years...
Post by Björn Kahl
Post by Durval Menezes
Yesterday, the machine was inadvertently powered off without a proper
# zfs mount testpool
cannot open 'testpool': dataset does not exist
# zfs list
no datasets available
Can anyone offer any help on how to recover from this? I've searched
both this list and the Web at large, but failed to find anything
really related to my situation.
Not enough data.
You are right, sorry. I should have been more verbose.
Post by Björn Kahl
Is the disk still there?
Yep: the disk is there, my system log has no messages related to any errors
on it, and smartctl -a shows absolutely no issues (no errors in the disk's
smart log, all problem counters like
Reallocated_Sector_Ct, Current_Pending_Sector, etc are all zero, and the
disk has just went through a SMART long test which also completed without
any errors).
Post by Björn Kahl
Has it possibly been renamed by the kernel? I.e. is /dev/sda6 still
named sda6 after the latest reboot?
Nope; just checked and sda6 is the same as always. An "hexdump -C
/dev/sda6" even shows me a lot of zfs-suggestive strings on it...
Post by Björn Kahl
Anything interesting in the logs?
Nothing at all. I routinely log ALL syslog messages (ie, "*.*") to a
single file, and I have just checked it in minute detail, but could find
nothing at all: no disk messages, no zfs messages, nothing.
Post by Björn Kahl
What says zpool status -v?
# zpool status -v
no pools available

What says zpool import?
Haven't tried yet. Is it perfectly safe (ie, completely read-only)? Or
should I make a copy of the partition first?

Thanks for the help,
--
Durval Menezes.
--
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Ryan How
2012-06-15 01:15:17 UTC
Permalink
zpool import just lists the pools available for importing. It's probably
exactly what you need :)

usually the system remembers what was already imported in the system and
automatically brings it in, but something may have happened and it "forgot".
--
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Durval Menezes
2012-06-15 01:44:25 UTC
Permalink
Hi Ryan,
Post by Ryan How
zpool import just lists the pools available for importing.
You mean, it walks though all disk devices and then looks for signatures
there, printing the ones it founds?

It's probably exactly what you need :)
I've started a network copy of that partition to my desktop... will wait
for it to finish before continuing, just for the extra peace of mind ;-)
Post by Ryan How
usually the system remembers what was already imported in the system and
automatically brings it in, but something may have happened and it "forgot".
Humrmrmrmr... pray tell, where would the system "store" that info? A flag
or something at each pool "superblock" or whatever?

Cheers,
--
Durval.
Post by Ryan How
--
To visit our Web site, click on http://zfs-fuse.net/
--
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Ryan How
2012-06-15 04:47:18 UTC
Permalink
I think it is some zfs cache file, /etc/zfs.cache or something, don't
really have much idea :). But I run ZFS on a live linux system and have
to import the zpools every time because that file isn't persisted.

So it doesn't store it on the zfs disk. I guess it must be like the zfs
version of fstab

Because you didn't export the disk, you might have to do a force on the
import. Don't be scared, I've done it a million times and I'm a bit of a
newbie to zfs and haven't managed to lose anything yet :).

Cheers,

Ryan
Post by Durval Menezes
Hi Ryan,
zpool import just lists the pools available for importing.
You mean, it walks though all disk devices and then looks for
signatures there, printing the ones it founds?
It's probably exactly what you need :)
I've started a network copy of that partition to my desktop... will
wait for it to finish before continuing, just for the extra peace of
mind ;-)
usually the system remembers what was already imported in the
system and automatically brings it in, but something may have
happened and it "forgot".
Humrmrmrmr... pray tell, where would the system "store" that info? A
flag or something at each pool "superblock" or whatever?
Cheers,
--
Durval.
--
To visit our Web site, click on http://zfs-fuse.net/
--
To visit our Web site, click on http://zfs-fuse.net/
--
To post to this group, send email to zfs-fuse-/***@public.gmane.org
To visit our Web site, click on http://zfs-fuse.net/
Durval Menezes
2012-06-16 23:34:27 UTC
Permalink
Hello folks,

After finishing and verifying my full-partition dd copy to another machine,
I finally ran (with great anticipation) the "zpool import" command, here's
how it went:

# zpool import
pool: testpool
id: 1571407782190788899
state: ONLINE
action: The pool can be imported using its name or numeric identifier.
config:

testpool ONLINE
sda6 ONLINE

And then:
# zpool import testpool
(took a few seconds, and didn't output anything).

At the end of it, the disappeared pool was imported and even mounted, so I
didn't even had to do a "zfs mount" on it, and it now shows on "zfs list"
too:

# zfs list
NAME USED AVAIL REFER MOUNTPOINT
testpool 186G 13.0G 186G /testpool

So I guess it's fully recovered now... just to make sure everything is
alright, I started a "zpool scrub" on the pool, waiting for it to finish...
still 4h to go, but I don't anticipate any further problems.

Thanks to everyone for the help.

Cheers,
--
Durval.
Post by Ryan How
I think it is some zfs cache file, /etc/zfs.cache or something, don't
really have much idea :). But I run ZFS on a live linux system and have to
import the zpools every time because that file isn't persisted.
So it doesn't store it on the zfs disk. I guess it must be like the zfs
version of fstab
Because you didn't export the disk, you might have to do a force on the
import. Don't be scared, I've done it a million times and I'm a bit of a
newbie to zfs and haven't managed to lose anything yet :).
Cheers,
Ryan
Hi Ryan,
Post by Ryan How
zpool import just lists the pools available for importing.
You mean, it walks though all disk devices and then looks for signatures
there, printing the ones it founds?
It's probably exactly what you need :)
I've started a network copy of that partition to my desktop... will wait
for it to finish before continuing, just for the extra peace of mind ;-)
Post by Ryan How
usually the system remembers what was already imported in the system and
automatically brings it in, but something may have happened and it "forgot".
Humrmrmrmr... pray tell, where would the system "store" that info? A
flag or something at each pool "superblock" or whatever?
Cheers,
--
Durval.
Post by Ryan How
--
To visit our Web site, click on http://zfs-fuse.net/
--
To visit our Web site, click on http://zfs-fuse.net/
--
To visit our Web site, click on http://zfs-fuse.net/
--
To post to this group, send email to zfs-fuse-/***@public.gmane.org
To visit our Web site, click on http://zfs-fuse.net/
Christ Schlacta
2012-06-17 00:11:53 UTC
Permalink
Before you add sizable data to the new disk, you should attempt to
reboot the system again just to be certain, however, it should just
continue to just work again now.
Post by Durval Menezes
Hello folks,
After finishing and verifying my full-partition dd copy to another
machine, I finally ran (with great anticipation) the "zpool import"
# zpool import
pool: testpool
id: 1571407782190788899
state: ONLINE
action: The pool can be imported using its name or numeric identifier.
testpool ONLINE
sda6 ONLINE
# zpool import testpool
(took a few seconds, and didn't output anything).
At the end of it, the disappeared pool was imported and even mounted,
so I didn't even had to do a "zfs mount" on it, and it now shows on
# zfs list
NAME USED AVAIL REFER MOUNTPOINT
testpool 186G 13.0G 186G /testpool
So I guess it's fully recovered now... just to make sure everything is
alright, I started a "zpool scrub" on the pool, waiting for it to
finish... still 4h to go, but I don't anticipate any further problems.
Thanks to everyone for the help.
Cheers,
--
Durval.
I think it is some zfs cache file, /etc/zfs.cache or something,
don't really have much idea :). But I run ZFS on a live linux
system and have to import the zpools every time because that file
isn't persisted.
So it doesn't store it on the zfs disk. I guess it must be like
the zfs version of fstab
Because you didn't export the disk, you might have to do a force
on the import. Don't be scared, I've done it a million times and
I'm a bit of a newbie to zfs and haven't managed to lose anything
yet :).
Cheers,
Ryan
Post by Durval Menezes
Hi Ryan,
zpool import just lists the pools available for importing.
You mean, it walks though all disk devices and then looks for
signatures there, printing the ones it founds?
It's probably exactly what you need :)
I've started a network copy of that partition to my desktop...
will wait for it to finish before continuing, just for the extra
peace of mind ;-)
usually the system remembers what was already imported in the
system and automatically brings it in, but something may have
happened and it "forgot".
Humrmrmrmr... pray tell, where would the system "store" that
info? A flag or something at each pool "superblock" or whatever?
Cheers,
--
Durval.
--
To post to this group, send email to
To visit our Web site, click on http://zfs-fuse.net/
--
To visit our Web site, click on http://zfs-fuse.net/
--
To visit our Web site, click on http://zfs-fuse.net/
--
To visit our Web site, click on http://zfs-fuse.net/
--
To post to this group, send email to zfs-fuse-/***@public.gmane.org
To visit our Web site, click on http://zfs-fuse.net/
Durval Menezes
2012-06-17 00:44:10 UTC
Permalink
Hello Christ,
Before you add sizable data to the new disk, you should attempt to reboot
the system again just to be certain, however, it should just continue to
just work again now.
Will do, right after my "zfs scrub" finishes (63.5% done already, and no
errors so far...)

Thanks for the tip,
--
Durval Menezes.
Hello folks,
After finishing and verifying my full-partition dd copy to another
machine, I finally ran (with great anticipation) the "zpool import"
# zpool import
pool: testpool
id: 1571407782190788899
state: ONLINE
action: The pool can be imported using its name or numeric identifier.
testpool ONLINE
sda6 ONLINE
# zpool import testpool
(took a few seconds, and didn't output anything).
At the end of it, the disappeared pool was imported and even mounted, so
I didn't even had to do a "zfs mount" on it, and it now shows on "zfs list"
# zfs list
NAME USED AVAIL REFER MOUNTPOINT
testpool 186G 13.0G 186G /testpool
So I guess it's fully recovered now... just to make sure everything is
alright, I started a "zpool scrub" on the pool, waiting for it to finish...
still 4h to go, but I don't anticipate any further problems.
Thanks to everyone for the help.
Cheers,
--
Durval.
Post by Ryan How
I think it is some zfs cache file, /etc/zfs.cache or something, don't
really have much idea :). But I run ZFS on a live linux system and have to
import the zpools every time because that file isn't persisted.
So it doesn't store it on the zfs disk. I guess it must be like the zfs
version of fstab
Because you didn't export the disk, you might have to do a force on the
import. Don't be scared, I've done it a million times and I'm a bit of a
newbie to zfs and haven't managed to lose anything yet :).
Cheers,
Ryan
Hi Ryan,
Post by Ryan How
zpool import just lists the pools available for importing.
You mean, it walks though all disk devices and then looks for signatures
there, printing the ones it founds?
It's probably exactly what you need :)
I've started a network copy of that partition to my desktop... will
wait for it to finish before continuing, just for the extra peace of mind
;-)
Post by Ryan How
usually the system remembers what was already imported in the system and
automatically brings it in, but something may have happened and it "forgot".
Humrmrmrmr... pray tell, where would the system "store" that info? A
flag or something at each pool "superblock" or whatever?
Cheers,
--
Durval.
Post by Ryan How
--
To visit our Web site, click on http://zfs-fuse.net/
--
To visit our Web site, click on http://zfs-fuse.net/
--
To visit our Web site, click on http://zfs-fuse.net/
--
To visit our Web site, click on http://zfs-fuse.net/
--
To visit our Web site, click on http://zfs-fuse.net/
--
To post to this group, send email to zfs-fuse-/***@public.gmane.org
To visit our Web site, click on http://zfs-fuse.net/
Durval Menezes
2012-06-17 02:24:01 UTC
Permalink
Hello Folks,

Just to keep everyone posted: the scrub finished with no errors whatsoever,
and I've just rebooted the machine and the ZFS partition is now mounting
alright. so everything seems fully recovered.

Thanks everyone for the great help.

Cheers,
--
Durval.
Post by Durval Menezes
Hello Christ,
Post by Christ Schlacta
Before you add sizable data to the new disk, you should attempt to
reboot the system again just to be certain, however, it should just
continue to just work again now.
Will do, right after my "zfs scrub" finishes (63.5% done already, and no
errors so far...)
Thanks for the tip,
--
Durval Menezes.
Post by Christ Schlacta
Hello folks,
After finishing and verifying my full-partition dd copy to another
machine, I finally ran (with great anticipation) the "zpool import"
# zpool import
pool: testpool
id: 1571407782190788899
state: ONLINE
action: The pool can be imported using its name or numeric identifier.
testpool ONLINE
sda6 ONLINE
# zpool import testpool
(took a few seconds, and didn't output anything).
At the end of it, the disappeared pool was imported and even mounted,
so I didn't even had to do a "zfs mount" on it, and it now shows on "zfs
# zfs list
NAME USED AVAIL REFER MOUNTPOINT
testpool 186G 13.0G 186G /testpool
So I guess it's fully recovered now... just to make sure everything is
alright, I started a "zpool scrub" on the pool, waiting for it to finish...
still 4h to go, but I don't anticipate any further problems.
Thanks to everyone for the help.
Cheers,
--
Durval.
Post by Ryan How
I think it is some zfs cache file, /etc/zfs.cache or something, don't
really have much idea :). But I run ZFS on a live linux system and have to
import the zpools every time because that file isn't persisted.
So it doesn't store it on the zfs disk. I guess it must be like the zfs
version of fstab
Because you didn't export the disk, you might have to do a force on the
import. Don't be scared, I've done it a million times and I'm a bit of a
newbie to zfs and haven't managed to lose anything yet :).
Cheers,
Ryan
Hi Ryan,
Post by Ryan How
zpool import just lists the pools available for importing.
You mean, it walks though all disk devices and then looks for signatures
there, printing the ones it founds?
It's probably exactly what you need :)
I've started a network copy of that partition to my desktop... will
wait for it to finish before continuing, just for the extra peace of mind
;-)
Post by Ryan How
usually the system remembers what was already imported in the system
and automatically brings it in, but something may have happened and it
"forgot".
Humrmrmrmr... pray tell, where would the system "store" that info? A
flag or something at each pool "superblock" or whatever?
Cheers,
--
Durval.
Post by Ryan How
--
To visit our Web site, click on http://zfs-fuse.net/
--
To visit our Web site, click on http://zfs-fuse.net/
--
To visit our Web site, click on http://zfs-fuse.net/
--
To visit our Web site, click on http://zfs-fuse.net/
--
To visit our Web site, click on http://zfs-fuse.net/
--
To post to this group, send email to zfs-fuse-/***@public.gmane.org
To visit our Web site, click on http://zfs-fuse.net/
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