not enough operational mirrors

not enough operational mirrors

[Ian Young]

My 6-drive software RAID 10 array failed.  The individual drives
failed one at a time over the past few months but it's been an
extremely busy summer and I didn't have the free time to RMA the
drives and rebuild the array.  Now I'm wishing I had acted sooner
because three of the drives are marked as removed and the array
doesn't have enough mirrors to start.  I followed the recovery
instructions at raid.wiki.kernel.org and, before making things any
worse, saved the status using mdadm --examine and consulted this
mailing list.  Here's the status:

http://pastebin.com/KkV8e8Gq

I can see that the event counts on sdd2 and sdf2 are significantly far
behind, so we can consider that data too old.  sdc2 is only behind by
two events, so any data loss there should be minimal.  If I can make
the array start with sd[abce]2 I think that will be enough to mount
the filesystem, back up my data, and start replacing drives.  How do I
do that?

Re: not enough operational mirrors

[NeilBrown]

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On Sun, 21 Sep 2014 22:32:19 -0700 Ian Young <ian@duffrecords.com> wrote:

> My 6-drive software RAID 10 array failed.  The individual drives
> failed one at a time over the past few months but it's been an
> extremely busy summer and I didn't have the free time to RMA the
> drives and rebuild the array.  Now I'm wishing I had acted sooner
> because three of the drives are marked as removed and the array
> doesn't have enough mirrors to start.  I followed the recovery
> instructions at raid.wiki.kernel.org and, before making things any
> worse, saved the status using mdadm --examine and consulted this
> mailing list.  Here's the status:
> 
> http://pastebin.com/KkV8e8Gq
> 
> I can see that the event counts on sdd2 and sdf2 are significantly far
> behind, so we can consider that data too old.  sdc2 is only behind by
> two events, so any data loss there should be minimal.  If I can make
> the array start with sd[abce]2 I think that will be enough to mount
> the filesystem, back up my data, and start replacing drives.  How do I
> do that?

Use the "--force" option with "--assemble".

NeilBrown

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Re: not enough operational mirrors

[Ian Young]

I forced the three good disks and the one that was behind by two
events to assemble:

mdadm --assemble --force /dev/md0 /dev/sda2 /dev/sdb2 /dev/sdc2 /dev/sde2

Then I added the other two disks and let it sync overnight:

mdadm --add --force /dev/md0 /dev/sdd2
mdadm --add --force /dev/md0 /dev/sdf2

I rebooted the system in recovery mode and the root filesystem is
back!  However, / is read-only and my /srv partition, which is the
largest and has most of my data, can't mount.  When I try to examine
the array, it says "no md superblock detected on /dev/md0."  On top of
the software RAID, I have four logical volumes.  Here is the full LVM
configuration:

http://pastebin.com/gzdZq5DL

How do I recover the superblock?

On Sun, Sep 21, 2014 at 10:47 PM, NeilBrown <neilb@suse.de> wrote:
> On Sun, 21 Sep 2014 22:32:19 -0700 Ian Young <ian@duffrecords.com> wrote:
>
>> My 6-drive software RAID 10 array failed.  The individual drives
>> failed one at a time over the past few months but it's been an
>> extremely busy summer and I didn't have the free time to RMA the
>> drives and rebuild the array.  Now I'm wishing I had acted sooner
>> because three of the drives are marked as removed and the array
>> doesn't have enough mirrors to start.  I followed the recovery
>> instructions at raid.wiki.kernel.org and, before making things any
>> worse, saved the status using mdadm --examine and consulted this
>> mailing list.  Here's the status:
>>
>> http://pastebin.com/KkV8e8Gq
>>
>> I can see that the event counts on sdd2 and sdf2 are significantly far
>> behind, so we can consider that data too old.  sdc2 is only behind by
>> two events, so any data loss there should be minimal.  If I can make
>> the array start with sd[abce]2 I think that will be enough to mount
>> the filesystem, back up my data, and start replacing drives.  How do I
>> do that?
>
> Use the "--force" option with "--assemble".
>
> NeilBrown

Re: not enough operational mirrors

[NeilBrown]

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On Mon, 22 Sep 2014 10:17:46 -0700 Ian Young <ian@duffrecords.com> wrote:

> I forced the three good disks and the one that was behind by two
> events to assemble:
> 
> mdadm --assemble --force /dev/md0 /dev/sda2 /dev/sdb2 /dev/sdc2 /dev/sde2
> 
> Then I added the other two disks and let it sync overnight:
> 
> mdadm --add --force /dev/md0 /dev/sdd2
> mdadm --add --force /dev/md0 /dev/sdf2
> 
> I rebooted the system in recovery mode and the root filesystem is
> back!  However, / is read-only and my /srv partition, which is the
> largest and has most of my data, can't mount.  When I try to examine
> the array, it says "no md superblock detected on /dev/md0."  On top of
> the software RAID, I have four logical volumes.  Here is the full LVM
> configuration:
> 
> http://pastebin.com/gzdZq5DL
> 
> How do I recover the superblock?

What sort of filesystem is it?  ext4??

Try "fsck -n" and see if it finds anything.

The fact that LVM found everything suggests that the array is mostly
working.  Maybe just one superblock got corrupted somehow.  If 'fsck' doesn't
get you anywhere you might need to ask on a forum dedicated to the particular
filesystem.

NeilBrown


> 
> On Sun, Sep 21, 2014 at 10:47 PM, NeilBrown <neilb@suse.de> wrote:
> > On Sun, 21 Sep 2014 22:32:19 -0700 Ian Young <ian@duffrecords.com> wrote:
> >
> >> My 6-drive software RAID 10 array failed.  The individual drives
> >> failed one at a time over the past few months but it's been an
> >> extremely busy summer and I didn't have the free time to RMA the
> >> drives and rebuild the array.  Now I'm wishing I had acted sooner
> >> because three of the drives are marked as removed and the array
> >> doesn't have enough mirrors to start.  I followed the recovery
> >> instructions at raid.wiki.kernel.org and, before making things any
> >> worse, saved the status using mdadm --examine and consulted this
> >> mailing list.  Here's the status:
> >>
> >> http://pastebin.com/KkV8e8Gq
> >>
> >> I can see that the event counts on sdd2 and sdf2 are significantly far
> >> behind, so we can consider that data too old.  sdc2 is only behind by
> >> two events, so any data loss there should be minimal.  If I can make
> >> the array start with sd[abce]2 I think that will be enough to mount
> >> the filesystem, back up my data, and start replacing drives.  How do I
> >> do that?
> >
> > Use the "--force" option with "--assemble".
> >
> > NeilBrown


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Re: not enough operational mirrors

[Ian Young]

It's XFS.  I'm running:

 xfs_repair -n /dev/mapper/vg_raid10-srv

I expect it will take hours or days as this volume is 8.15 TiB.

On Mon, Sep 22, 2014 at 4:53 PM, NeilBrown <neilb@suse.de> wrote:
> On Mon, 22 Sep 2014 10:17:46 -0700 Ian Young <ian@duffrecords.com> wrote:
>
>> I forced the three good disks and the one that was behind by two
>> events to assemble:
>>
>> mdadm --assemble --force /dev/md0 /dev/sda2 /dev/sdb2 /dev/sdc2 /dev/sde2
>>
>> Then I added the other two disks and let it sync overnight:
>>
>> mdadm --add --force /dev/md0 /dev/sdd2
>> mdadm --add --force /dev/md0 /dev/sdf2
>>
>> I rebooted the system in recovery mode and the root filesystem is
>> back!  However, / is read-only and my /srv partition, which is the
>> largest and has most of my data, can't mount.  When I try to examine
>> the array, it says "no md superblock detected on /dev/md0."  On top of
>> the software RAID, I have four logical volumes.  Here is the full LVM
>> configuration:
>>
>> http://pastebin.com/gzdZq5DL
>>
>> How do I recover the superblock?
>
> What sort of filesystem is it?  ext4??
>
> Try "fsck -n" and see if it finds anything.
>
> The fact that LVM found everything suggests that the array is mostly
> working.  Maybe just one superblock got corrupted somehow.  If 'fsck' doesn't
> get you anywhere you might need to ask on a forum dedicated to the particular
> filesystem.
>
> NeilBrown
>
>
>>
>> On Sun, Sep 21, 2014 at 10:47 PM, NeilBrown <neilb@suse.de> wrote:
>> > On Sun, 21 Sep 2014 22:32:19 -0700 Ian Young <ian@duffrecords.com> wrote:
>> >
>> >> My 6-drive software RAID 10 array failed.  The individual drives
>> >> failed one at a time over the past few months but it's been an
>> >> extremely busy summer and I didn't have the free time to RMA the
>> >> drives and rebuild the array.  Now I'm wishing I had acted sooner
>> >> because three of the drives are marked as removed and the array
>> >> doesn't have enough mirrors to start.  I followed the recovery
>> >> instructions at raid.wiki.kernel.org and, before making things any
>> >> worse, saved the status using mdadm --examine and consulted this
>> >> mailing list.  Here's the status:
>> >>
>> >> http://pastebin.com/KkV8e8Gq
>> >>
>> >> I can see that the event counts on sdd2 and sdf2 are significantly far
>> >> behind, so we can consider that data too old.  sdc2 is only behind by
>> >> two events, so any data loss there should be minimal.  If I can make
>> >> the array start with sd[abce]2 I think that will be enough to mount
>> >> the filesystem, back up my data, and start replacing drives.  How do I
>> >> do that?
>> >
>> > Use the "--force" option with "--assemble".
>> >
>> > NeilBrown
>

Re: not enough operational mirrors

[Ian Young]

I booted from a live CD so I could use version 3.1.10 of xfs_repair
(versions < 3.1.8 reportedly have a bug when using ag_stride), then
ran the following command:

xfs_repair -P -o bhash=16384 -o ihash=16384 -o ag_stride=16
/dev/mapper/vg_raid10-srv

It stopped after a few seconds, saying:

xfs_repair: read failed: Input/output error
XFS: failed to find log head
zero_log: cannot find log head/tail (xlog_find_tail=5), zeroing it anyway
xfs_repair: libxfs_device_zero write failed: Input/output error

However, I was able to mount the volume after that and my data was
still there!  Thanks for pointing me in the right direction with the
RAID.

On Mon, Sep 22, 2014 at 5:55 PM, Ian Young <ian@duffrecords.com> wrote:
> It's XFS.  I'm running:
>
>  xfs_repair -n /dev/mapper/vg_raid10-srv
>
> I expect it will take hours or days as this volume is 8.15 TiB.
>
> On Mon, Sep 22, 2014 at 4:53 PM, NeilBrown <neilb@suse.de> wrote:
>> On Mon, 22 Sep 2014 10:17:46 -0700 Ian Young <ian@duffrecords.com> wrote:
>>
>>> I forced the three good disks and the one that was behind by two
>>> events to assemble:
>>>
>>> mdadm --assemble --force /dev/md0 /dev/sda2 /dev/sdb2 /dev/sdc2 /dev/sde2
>>>
>>> Then I added the other two disks and let it sync overnight:
>>>
>>> mdadm --add --force /dev/md0 /dev/sdd2
>>> mdadm --add --force /dev/md0 /dev/sdf2
>>>
>>> I rebooted the system in recovery mode and the root filesystem is
>>> back!  However, / is read-only and my /srv partition, which is the
>>> largest and has most of my data, can't mount.  When I try to examine
>>> the array, it says "no md superblock detected on /dev/md0."  On top of
>>> the software RAID, I have four logical volumes.  Here is the full LVM
>>> configuration:
>>>
>>> http://pastebin.com/gzdZq5DL
>>>
>>> How do I recover the superblock?
>>
>> What sort of filesystem is it?  ext4??
>>
>> Try "fsck -n" and see if it finds anything.
>>
>> The fact that LVM found everything suggests that the array is mostly
>> working.  Maybe just one superblock got corrupted somehow.  If 'fsck' doesn't
>> get you anywhere you might need to ask on a forum dedicated to the particular
>> filesystem.
>>
>> NeilBrown
>>
>>
>>>
>>> On Sun, Sep 21, 2014 at 10:47 PM, NeilBrown <neilb@suse.de> wrote:
>>> > On Sun, 21 Sep 2014 22:32:19 -0700 Ian Young <ian@duffrecords.com> wrote:
>>> >
>>> >> My 6-drive software RAID 10 array failed.  The individual drives
>>> >> failed one at a time over the past few months but it's been an
>>> >> extremely busy summer and I didn't have the free time to RMA the
>>> >> drives and rebuild the array.  Now I'm wishing I had acted sooner
>>> >> because three of the drives are marked as removed and the array
>>> >> doesn't have enough mirrors to start.  I followed the recovery
>>> >> instructions at raid.wiki.kernel.org and, before making things any
>>> >> worse, saved the status using mdadm --examine and consulted this
>>> >> mailing list.  Here's the status:
>>> >>
>>> >> http://pastebin.com/KkV8e8Gq
>>> >>
>>> >> I can see that the event counts on sdd2 and sdf2 are significantly far
>>> >> behind, so we can consider that data too old.  sdc2 is only behind by
>>> >> two events, so any data loss there should be minimal.  If I can make
>>> >> the array start with sd[abce]2 I think that will be enough to mount
>>> >> the filesystem, back up my data, and start replacing drives.  How do I
>>> >> do that?
>>> >
>>> > Use the "--force" option with "--assemble".
>>> >
>>> > NeilBrown
>>

Re: not enough operational mirrors

[Ian Young]

I've received two replacement drives and added them to the array.  One
of them finished synchronizing and became an active member.  The
other, sdf, has been treated as a spare.  After running a smartctl
test on each of the drives, I found that sde has errors, preventing
the sync process from making sdf an active member.  I have tried a
couple of recommendations I read on various sites, such as stopping
the array and recreating it with the "--assume-clean" option (not
possible because a process is using the array) and growing the array
one disk larger (not possible because this is RAID 10).  Should I try
to repair the bad blocks or is there a way to force sde and sdf to
sync first?

[root@localhost ~]# smartctl -l selftest /dev/sde
smartctl 6.2 2013-07-26 r3841 [x86_64-linux-3.6.10-4.fc18.x86_64] (local build)
Copyright (C) 2002-13, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF READ SMART DATA SECTION ===
SMART Self-test log structure revision number 1
Num  Test_Description    Status                  Remaining
LifeTime(hours)  LBA_of_first_error
# 1  Short offline       Completed: read failure       90%     11822
      1187144704
# 2  Short offline       Completed: read failure       90%     11814
      1187144704

On Tue, Sep 23, 2014 at 10:07 AM, Ian Young <ian@duffrecords.com> wrote:
> I booted from a live CD so I could use version 3.1.10 of xfs_repair
> (versions < 3.1.8 reportedly have a bug when using ag_stride), then
> ran the following command:
>
> xfs_repair -P -o bhash=16384 -o ihash=16384 -o ag_stride=16
> /dev/mapper/vg_raid10-srv
>
> It stopped after a few seconds, saying:
>
> xfs_repair: read failed: Input/output error
> XFS: failed to find log head
> zero_log: cannot find log head/tail (xlog_find_tail=5), zeroing it anyway
> xfs_repair: libxfs_device_zero write failed: Input/output error
>
> However, I was able to mount the volume after that and my data was
> still there!  Thanks for pointing me in the right direction with the
> RAID.
>
> On Mon, Sep 22, 2014 at 5:55 PM, Ian Young <ian@duffrecords.com> wrote:
>> It's XFS.  I'm running:
>>
>>  xfs_repair -n /dev/mapper/vg_raid10-srv
>>
>> I expect it will take hours or days as this volume is 8.15 TiB.
>>
>> On Mon, Sep 22, 2014 at 4:53 PM, NeilBrown <neilb@suse.de> wrote:
>>> On Mon, 22 Sep 2014 10:17:46 -0700 Ian Young <ian@duffrecords.com> wrote:
>>>
>>>> I forced the three good disks and the one that was behind by two
>>>> events to assemble:
>>>>
>>>> mdadm --assemble --force /dev/md0 /dev/sda2 /dev/sdb2 /dev/sdc2 /dev/sde2
>>>>
>>>> Then I added the other two disks and let it sync overnight:
>>>>
>>>> mdadm --add --force /dev/md0 /dev/sdd2
>>>> mdadm --add --force /dev/md0 /dev/sdf2
>>>>
>>>> I rebooted the system in recovery mode and the root filesystem is
>>>> back!  However, / is read-only and my /srv partition, which is the
>>>> largest and has most of my data, can't mount.  When I try to examine
>>>> the array, it says "no md superblock detected on /dev/md0."  On top of
>>>> the software RAID, I have four logical volumes.  Here is the full LVM
>>>> configuration:
>>>>
>>>> http://pastebin.com/gzdZq5DL
>>>>
>>>> How do I recover the superblock?
>>>
>>> What sort of filesystem is it?  ext4??
>>>
>>> Try "fsck -n" and see if it finds anything.
>>>
>>> The fact that LVM found everything suggests that the array is mostly
>>> working.  Maybe just one superblock got corrupted somehow.  If 'fsck' doesn't
>>> get you anywhere you might need to ask on a forum dedicated to the particular
>>> filesystem.
>>>
>>> NeilBrown
>>>
>>>
>>>>
>>>> On Sun, Sep 21, 2014 at 10:47 PM, NeilBrown <neilb@suse.de> wrote:
>>>> > On Sun, 21 Sep 2014 22:32:19 -0700 Ian Young <ian@duffrecords.com> wrote:
>>>> >
>>>> >> My 6-drive software RAID 10 array failed.  The individual drives
>>>> >> failed one at a time over the past few months but it's been an
>>>> >> extremely busy summer and I didn't have the free time to RMA the
>>>> >> drives and rebuild the array.  Now I'm wishing I had acted sooner
>>>> >> because three of the drives are marked as removed and the array
>>>> >> doesn't have enough mirrors to start.  I followed the recovery
>>>> >> instructions at raid.wiki.kernel.org and, before making things any
>>>> >> worse, saved the status using mdadm --examine and consulted this
>>>> >> mailing list.  Here's the status:
>>>> >>
>>>> >> http://pastebin.com/KkV8e8Gq
>>>> >>
>>>> >> I can see that the event counts on sdd2 and sdf2 are significantly far
>>>> >> behind, so we can consider that data too old.  sdc2 is only behind by
>>>> >> two events, so any data loss there should be minimal.  If I can make
>>>> >> the array start with sd[abce]2 I think that will be enough to mount
>>>> >> the filesystem, back up my data, and start replacing drives.  How do I
>>>> >> do that?
>>>> >
>>>> > Use the "--force" option with "--assemble".
>>>> >
>>>> > NeilBrown
>>>

Re: not enough operational mirrors

[Ian Young]

Oops, I meant to say the error I get when trying to mount /srv is this:

root@dtla:~# mount /srv
mount: /dev/mapper/vg_raid10-srv: can't read superblock

Aren't there other copies of the superblock?  I'm not sure how it
works with LVM.

On Mon, Sep 22, 2014 at 10:17 AM, Ian Young <ian@duffrecords.com> wrote:
> I forced the three good disks and the one that was behind by two events to
> assemble:
>
> mdadm --assemble --force /dev/md0 /dev/sda2 /dev/sdb2 /dev/sdc2 /dev/sde2
>
> Then I added the other two disks and let it sync overnight:
>
> mdadm --add --force /dev/md0 /dev/sdd2
> mdadm --add --force /dev/md0 /dev/sdf2
>
> I rebooted the system in recovery mode and the root filesystem is back!
> However, / is read-only and my /srv partition, which is the largest and has
> most of my data, can't mount.  When I try to examine the array, it says "no
> md superblock detected on /dev/md0."  On top of the software RAID, I have
> four logical volumes.  Here is the full LVM configuration:
>
> http://pastebin.com/gzdZq5DL
>
> How do I recover the superblock?
>
> On Sun, Sep 21, 2014 at 10:47 PM, NeilBrown <neilb@suse.de> wrote:
>>
>> On Sun, 21 Sep 2014 22:32:19 -0700 Ian Young <ian@duffrecords.com> wrote:
>>
>> > My 6-drive software RAID 10 array failed.  The individual drives
>> > failed one at a time over the past few months but it's been an
>> > extremely busy summer and I didn't have the free time to RMA the
>> > drives and rebuild the array.  Now I'm wishing I had acted sooner
>> > because three of the drives are marked as removed and the array
>> > doesn't have enough mirrors to start.  I followed the recovery
>> > instructions at raid.wiki.kernel.org and, before making things any
>> > worse, saved the status using mdadm --examine and consulted this
>> > mailing list.  Here's the status:
>> >
>> > http://pastebin.com/KkV8e8Gq
>> >
>> > I can see that the event counts on sdd2 and sdf2 are significantly far
>> > behind, so we can consider that data too old.  sdc2 is only behind by
>> > two events, so any data loss there should be minimal.  If I can make
>> > the array start with sd[abce]2 I think that will be enough to mount
>> > the filesystem, back up my data, and start replacing drives.  How do I
>> > do that?
>>
>> Use the "--force" option with "--assemble".
>>
>> NeilBrown
>
>