[LU-5127] Running mke2fs to get alternate superblocks on >16TB LUN

• Status: Closed
• Project: Lustre
• Affects Version/s: Lustre 2.4.1
• Type: Question/Request
• Priority: Critical
• Reporter: Blake Caldwell
• Assignee: Jian Yu
• Resolution: Fixed

Environment

RHEL 6.4
e2fsprogs 1.42.9.wc1

Description

We have an OST that is not mountable because a superblock is unreadable from the backend storage. In order to begin repairs, we need to run mke2fs to get the alternate superblocks to then run debugfs. Unfortunately, the current version of e2fsprogs does not handle this by default. Can you advise the correct options to use with mke2fs with -n (very important!). If we run with -O64bit without any other of the original filesystem options, will that do it?

[root@f1-oss1d5 share]# /tmp/e2fsprogs-new/sbin/mke2fs -n /dev/mapper/f1-ddn1d-l30
mke2fs 1.42.9.wc1 (24-Feb-2014)
mke2fs: Size of device (0x151e00000 blocks) /dev/mapper/f1-ddn1d-l30 too big to be expressed
in 32 bits using a blocksize of 4096.

[root@f1-oss1d5 man8]# dumpe2fs /dev/mapper/f1-ddn1d-l30 | grep superblock
dumpe2fs 1.42.7.wc2 (07-Nov-2013)
dumpe2fs: Attempt to read block from filesystem resulted in short read while trying to open /dev/mapper/f1-ddn1d-l30
Couldn't find valid filesystem superblock.
[root@f1-oss1d5 man8]#

Comments

[Peter Jones]

Yu, Jian

Could you please advise here?

Thanks

Peter

[Blake Caldwell]

Hello,

We were able to resolve this issue. The -t ext4 option was critical to get mke2fs to assume the 64bit feature. Here are the full commands that we used.

[root@f1-oss1d1 ~]# mke2fs -n -t ext4 -O has_journal,ext_attr,resize_inode,dir_index,filetype,extent,64bit,mmp,flex_bg,sparse_super,large_file,huge_file,uninit_bg,dir_nlink,quota /dev/mapper/f1-ddn1d-l30
mke2fs 1.42.7.wc2 (07-Nov-2013)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=256 blocks, Stripe width=256 blocks
354287616 inodes, 5668601856 blocks
283430092 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=7816085504
172992 block groups
32768 blocks per group, 32768 fragments per group
2048 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968,
102400000, 214990848, 512000000, 550731776, 644972544, 1934917632,
2560000000, 3855122432

[root@f1-oss1d1 ~]# debugfs -b 4096 -s 32768 -c -R 'icheck 3992983288' /dev/mapper/f1-ddn1d-l30

[Jian Yu]

Hi Blake,

For -O option, you can only specify the features which are not listed in the [defaults] section and [fs_types] subsectionin in the /etc/mke2fs.conf configuration file.

Is there anything else I can help in this ticket?

[Blake Caldwell]

That answers it. Thanks!

[Jian Yu]

You're welcome, Blake. May I close this ticket?

[Blake Caldwell]

Yes. Please do.