btrfs w/ckd

btrfs w/ckd

[kathleen.hodge]

Hello,
I'm trying to use mod3 ckds which are already RAID10 protection. (most =
of the doc I'm looking at uses fba instead of ckd, so I didn't know if =
this was a limitation)
I'm addressing the head device and able to use these devices with no pr=
oblem as ext3.  I've been reading that cache may remember that it used =
to be ext3, so I detached and reattached, but get the same result when =
trying to mount after formatting.

I use the following to make the file system after I've attached, varied=
 online, formated and partitioned (also tried without the journaling sw=
itch).
mke2fs -j -t btrfs /dev/dasdbj1

Then the mount command:
mount -t btrfs /dev/dasdbj1 /home/sdasd/d01
mount: /dev/dasdbj1: can't read superblock

Can you please give me some direction?Thanks,
          Kathy Hodge

           EMC=B2
Mainframe Software QA
Phone:  1-508-293-6121 x76121
Cell:      1-303 -887-9292
Email:    kathleen.hodge@emc.com



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Re: btrfs w/ckd

[Hugo Mills]

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On Thu, Jun 02, 2011 at 03:45:07PM -0400, kathleen.hodge@emc.com wrote:
> Hello,
> I'm trying to use mod3 ckds which are already RAID10 protection. (most of the doc I'm looking at uses fba instead of ckd, so I didn't know if this was a limitation)
> I'm addressing the head device and able to use these devices with no problem as ext3.  I've been reading that cache may remember that it used to be ext3, so I detached and reattached, but get the same result when trying to mount after formatting.
> 
> I use the following to make the file system after I've attached, varied online, formated and partitioned (also tried without the journaling switch).
> mke2fs -j -t btrfs /dev/dasdbj1

   Quoting the man page for that command:

"mke2fs  is used to create an ext2, ext3, or ext4 filesystem, [...]"

The -t option specifies which of ext2, ext3, and ext4 to create.  I'm
surprised it did anything at all given a type of "btrfs"...

   You probably wanted mkfs.btrfs instead:

# mkfs.btrfs -d single -m single /dev/dasdbj1

> Then the mount command:
> mount -t btrfs /dev/dasdbj1 /home/sdasd/d01
> mount: /dev/dasdbj1: can't read superblock

   If it created an ext2/3/4 filesystem, I'm not entirely surprised
that it can't find a btrfs superblock there. :)

   Hugo.

-- 
=== Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk ===
  PGP key: 515C238D from wwwkeys.eu.pgp.net or http://www.carfax.org.uk
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Re: btrfs w/ckd

[Hugo Mills]

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   Hi, Kathleen,

On Thu, Jun 02, 2011 at 04:20:55PM -0400, kathleen.hodge@emc.com wrote:
> Hi Hugo, I don't seem to have mkfs.btrfs.  Here is the Red Hat 6.0 version I'm running, should it be included?
> 
> Linux LN164088.LSS.EMC.COM 2.6.32-71.el6.s390x #1 SMP Wed Sep 1 01:38:33 EDT 2010 s390x s390x s390x GNU/Linux

   OK, first -- kernel 2.6.32 is *massively* old in btrfs terms. There
are a whole bunch of pretty serious bugs that have been fixed between
then and now. You should really be running a kernel no earlier than
2.6.38: version 2.6.39 is preferable.

   You should also be using the latest btrfs-progs from the git
repository:

$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-progs-unstable.git
$ git co tmp
$ make
$ sudo make install

   (You may need the libuuid-devel package to get this to build.
There's also a problem with the most recent gcc, but that probably
won't apply to you; it's easily dealt with if you do hit it).

   Once you've made and installed btrfs-progs, you will have
mkfs.btrfs, and the btrfs tool, which is used for managing your
filesystem.

   You should also ensure that you're keeping good and regular backups
of the data in your filesystem, and be prepared to use them -- btrfs
is still considered experimental, and if things go wrong, the fastest
way at the moment to get your data back is often to restore from
backups.

   Hugo.

-- 
=== Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk ===
  PGP key: 515C238D from wwwkeys.eu.pgp.net or http://www.carfax.org.uk
     --- "I don't like the look of it,  I tell you." "Well, stop ---     
                          looking at it, then."                          

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