[LU-3559] MGS formatted with Lustre 2.1 cannot be started with Lustre 2.4

• Type: Bug
• Resolution: Fixed
• Priority: Blocker
• Fix Version/s: Lustre 2.4.1, Lustre 2.5.0
• Affects Version/s: Lustre 2.4.0, Lustre 2.5.0
• Severity: 3
• Assignee: Bruno Faccini (Inactive)
• Reporter: Sebastien Buisson (Inactive)

Description

With Lustre 2.1, I format an MGS with the follwing command:

mkfs.lustre --reformat --quiet --fsname=migrate --mgs
--mkfsoptions="-m 0" --device-size=204800 /root/mgt

Before starting this MGS, tunefs.lustre gives:

# tunefs.lustre --print /root/mgt
checking for existing Lustre data: found CONFIGS/mountdata
Reading CONFIGS/mountdata

   Read previous values:
Target:     MGS
Index:      unassigned
Lustre FS:  migrate
Mount type: ldiskfs
Flags:      0x74
              (MGS needs_index first_time update )
Persistent mount opts: user_xattr,errors=remount-ro
Parameters:


   Permanent disk data:
Target:     MGS
Index:      unassigned
Lustre FS:  migrate
Mount type: ldiskfs
Flags:      0x74
              (MGS needs_index first_time update )
Persistent mount opts: user_xattr,errors=remount-ro
Parameters:

Still with Lustre 2.1, I successfully start this MGS, and afterwards tunefs.lustre gives:

# tunefs.lustre --print /root/mgt
checking for existing Lustre data: found CONFIGS/mountdata
Reading CONFIGS/mountdata

   Read previous values:
Target:     MGS
Index:      unassigned
Lustre FS:  migrate
Mount type: ldiskfs
Flags:      0x74
              (MGS needs_index first_time update )
Persistent mount opts: user_xattr,errors=remount-ro
Parameters:


   Permanent disk data:
Target:     MGS
Index:      unassigned
Lustre FS:  migrate
Mount type: ldiskfs
Flags:      0x74
              (MGS needs_index first_time update )
Persistent mount opts: user_xattr,errors=remount-ro
Parameters:

Then I update to Lustre 2.4 on my node, and when I try to start this MGS I get:

# mount -t lustre -o loop /root/mgt /mnt/migrate/mgt
mount.lustre.orig: /dev/loop0 has no index assigned (probably formatted with old mkfs)

In Lustre 2.4, it seems mount.lustre requires every target, including MGT, to have an index. But with Lustre 2.1, MGTs can be formatted without specifying an index, and this is the way all our customers did. So if these customers migrate to Lustre 2.4, they will not be able to start their MGS.

I will propose a patch for mount.lustre in Lustre 2.4 to address this issue.

Sebastien.

Issue Links

• is related to: LU-2022 MGS fails to mount due to "has no index assigned (probably formatted with old mkfs" error