Re: mdadm raid6 recovery status

[NeilBrown <neilb@suse.de>]

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On Fri, 30 Mar 2012 21:22:34 +0000 "Paramasivam, Meenakshisundaram"
<mparamas@iupui.edu> wrote:

> 
> Thanks. Is it safe to fsck -n (and then fsck -y) on /dev/md2 when sdg is just added to md2 and is in "spare rebulding" status and recovery is only at 4% completed? BTW, we got all of the data backed up.

It is certainly safe to "fsck -n" while there is a spare rebuilding.  Each
process will slow down the other but that shouldn't be a problem.
I would never say that "fsck -y" is safe without seeing the output for "fsck
-n" however the rebuilding the spare should affect the safety of "fsck -y".

And it is always nice to hear that people have their data safe -  thanks.

NeilBrown


> 
> Background:
> When we assembled md2 we forced rest of the drives and did not include this drive. After 24 hrs, when I tried to assemble all of the drives into md2, I got "md: kicking non-fresh sdg from array!" message through dmesg, and was removed from md2 (through mdadm --detail). I just did:
> # mdadm /dev/md2 --add /dev/sdg
> mdadm: re-added /dev/sdg
> 
> Sundar
> 
> ________________________________________
> From: NeilBrown [neilb@suse.de]
> Sent: Thursday, March 29, 2012 3:41 PM
> To: Paramasivam, Meenakshisundaram
> Cc: linux-raid@vger.kernel.org
> Subject: Re: mdadm raid6 recovery status
> 
> On Thu, 29 Mar 2012 18:47:14 +0000 "Paramasivam, Meenakshisundaram"
> <mparamas@iupui.edu> wrote:
> 
> >
> > Clarification:
> > >>should I do new array creation
> > I meant running newfs on assembled 12 TB array, and restore data from backup, to resolve "df" reporting problem.
> 
> I would suggest asking on
>     linux-ext4@vger.kernel.org
> 
> be sure to give lots of details - kernel version etc.
> It would be worth running
>    fsck -n /dev/md2
> first and see if it reports anything strange.
> Maybe  just a fsck will fix it.
> 
> NeilBrown
> 
> 
> >
> > ________________________________________
> > From: Paramasivam, Meenakshisundaram
> > Sent: Thursday, March 29, 2012 1:33 PM
> > To: NeilBrown
> > Cc: linux-raid@vger.kernel.org
> > Subject: RE: mdadm raid6 recovery status
> >
> > Good news: Got ALL of our data back. [Actually it was 4.96TB not 7TB].
> >                      mdadm is a good one.
> >
> > Bad news: "df" is reporting wrong, while "du" is showing full size.
> > # df -kl /myarray
> > Filesystem           1K-blocks      Used Available Use% Mounted on
> > /dev/md2             11537161976    162432 10950945196   1% /myarray
> > # du -sk /myarray
> > 5326133556      /myarray
> > #
> >
> > I never looked into du or looked in depth of the files & folders and simply got mislead by reported "df" usage; data was there all along. We definitely want "df" for the array's filesystem (ext3) to report right.
> >
> > Now that we are backing up all of the data (at 400 Mbps) over network, I want to know if "df" reporting can be fixed easily or should I do new array creation and restore data from backup.
> >
> > We are ordering a new RAID card, just to be on safer side.
> >
> > Sundar
> >
> > ________________________________________
> > From: NeilBrown [neilb@suse.de]
> > Sent: Wednesday, March 28, 2012 7:27 PM
> > To: Paramasivam, Meenakshisundaram
> > Cc: linux-raid@vger.kernel.org
> > Subject: Re: mdadm raid6 recovery status
> >
> > On Wed, 28 Mar 2012 12:49:18 +0000 "Paramasivam, Meenakshisundaram"
> > <mparamas@iupui.edu> wrote:
> >
> > > [root@in-rady-neuro9 ~]# df -kl /myarray
> > > Filesystem           1K-blocks      Used Available Use% Mounted on
> > > /dev/md2             11537161976    162432 10950945196   1% /myarray
> > > Should be 7TB of used space.
> >
> > This is bad.  Something has happened to your filesystem.
> > It is almost as though someone ran "mkfs" on the array.
> > I don't know much about recovery after such an action, but I doubt you
> > will get much back.
> >
> > >
> > > [root@in-rady-neuro9 ~]# cat /proc/partitions
> > > major minor  #blocks  name
> > >
> > >    8        0  438960128 sda
> > >    8        1     512000 sda1
> > >    8        2   51200000 sda2
> > >    8        3  387247104 sda3
> > >    8       16 1953514584 sdb
> > >    8       32 1953514584 sdc
> > >    8       48 1953514584 sdd
> > >    8       64 1953514584 sde
> > >    8       80 1953514584 sdf
> > >    8       96 1953514584 sdg
> > >    8      112 1953514584 sdh
> > >    8      128 1953514584 sdi
> > >  253        0  346226688 dm-0
> > >  253        1   40992768 dm-1
> >
> > No md2 ???
> >
> > >
> > > sd[b-i] are raid devices
> > >
> > > [root@in-rady-neuro9 ~]# mdadm --detail /dev/md2
> > > /dev/md2:
> > >         Version : 0.90
> > >   Creation Time : Fri Dec 16 17:56:14 2011
> > >      Raid Level : raid6
> > >      Array Size : 11721086976 (11178.10 GiB 12002.39 GB)
> > >   Used Dev Size : 1953514496 (1863.02 GiB 2000.40 GB)  <<<====== Wrong! Should be 7TB of used array space.
> >
> > "Used Dev Size" isn't "how much of the array is used by the filesystem" -
> > mdadm doesn't know anything about filesystems.
> > It is "How much of each individual device is used by the array", which is
> > usually a little less than the size of the smallest device.
> > So 2TB is correct here.
> >
> >
> > NeilBrown
> >
> >
> 


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