[lustre-discuss] Cannot mount MDT after upgrading from Lustre 2.12.6 to 2.15.3

Tue Sep 26 18:57:38 PDT 2023

OK. Let me provide more details about the upgrade from 2.12.X to 2.15.X.

We have several production clusters. Due to different requirements and
hardware, each has slightly different Lustre configurations. Our Linux
distribution is Debian. Sometimes due to hardware spec, we need to use
different Linux kernel versions. So we always have to compile Kernel
(vanilla Linux kernel), MLNX_OFED, e2fsprog / ZFS, and Lustre. Here I
temporarily skip the compilation (that involved a lot of details), just
mention the upgrade procedure for two different cases.

1. Two of our clusters have Lustre-2.12.6, with MDT with ZFS backend, and
OST with ZFS backend, where ZFS is 0.7.13. From the compatibility list
mentioned in documentation, the upgrade involves both ZFS upgrade to 2.0.7
and Lustre upgrade to 2.15.X. It was very smooth and successful. The
procedure is:
    1) Compile and install new versions of Linux kernel, MLNX_OFED, ZFS,
and Lustre. Depending on the hardware, some servers we use Linux kernel
4.19.X + MLNX_OFED-4.6, or Linux kernel 4.19.X + MLNX_OFED-4.9, or Linux
kernel 5.4.X + MLNX_OFED-4.9. They are all compatible to Lustre-2.15.X and
ZFS-2.0.7.
     2) After installation of the new software, start up ZFS first:
```
modprobe zfs
zpool import <lustre_pool_name>
zpool status <lustre_pool_name>
```
         There will be messages about ZFS pool needs to be upgraded to
enable new features. But after upgrade, the ZFS pool will not be compatible
to the old ZFS version anymore. The command to upgrade ZFS pool is (for all
the MDT and OST pools):
```
zpool upgrade <lustre_pool_name>
zpool status <lustre_pool_name>
```
          Checking zpool status again, the warning messages were
disappeared.
    3) I checked the Lustre Operation Manual again, and saw that in the
recent version it does not need to run tunefs.lustre --writeconf command.
Sorry that it was my fault. But in our case, we run this command whenever
doing Lustre upgrade. Note that to run it, we have to run it in all the
Lustre MDT and OST pools. It cleared out the logs and will regenerate it
when mounting Lustre.

2. One of our clusters have Lustre-2.12.6, with MDT with ldiskfs backend,
and OST with ZFS backend, where ZFS is 0.7.13. We have to upgrade it to
e2fsprogs-1.47.0, ZFS-2.0.7 and Lustre-2.15.3. The upgrade of OST part is
exactly the same as the above, so I don't repeat. The major challenge is
MDT with ldiskfs. What I have done is
    1) After installing all the new version of the software, running
tunefs.lustre --writeconf (for all MDT and OST). Probably this is the wrong
step for the upgrade to Lustre-2.15.X.
    2) According to Lustre Operation manual chapter 17, to upgrade Lustre
from 2.13.0 and before to 2.15.X, we should run

tune2fs -O ea_inode /dev/*mdtdev*

After that, as I have posted, we encounter problem of mounting MDT. Then we
cure this problem by following the section 18 of Lustre Operation manual.

My personal suggestions are:
1. In the future, to do major revision upgrade for our production run
systems (say,  2.12.X to 2.15.X, or 2.15.X to 2.16 or later), I will
develop a small testing system, installing exactly the same software of the
production run, and test the upgrade, to make sure that every steps are
correct. We did this for upgrading Lustre with ZFS backend. But this time
due to time pressure, we skip this step for upgrading Lustre with ldiskfs
backend. I think no matter what situation, it is still worth to do this
step in order to avoid any risks.

2. Currently compiling Lustre with ldiskfs backend is still a nightmare.
The ldiskfs code is not a self-contained, stand along code. It actually
copied codes from the kernel ext4 code, did a lot of patches, and then did
the compilation, on the fly. So we have to be very careful to select the
Linux kernel, to select a compatible one for both our hardware and Lustre
version. The ZFS backend is much more cleaner. It is a stand along and
self-contained code. We don't need to do patches on the fly. So I would
like to suggest the Lustre developer to consider to make the ldiskfs to be
a stand along and self-contained code in the future release. That will
bring us a lot of convenient.

Hope that the above experiences could be useful to our community.

ps. Lustre Operation Manual:
https://doc.lustre.org/lustre_manual.xhtml#Upgrading_2.x

Best Regards,

T.H.Hsieh

Audet, Martin <Martin.Audet at cnrc-nrc.gc.ca> 於 2023年9月27日 週三 上午3:44寫道：

> Hello all,
>
>
> I would appreciate if the community would give more attention to this
> issue because upgrading from 2.12.x to 2.15.x, two LTS versions, is
> something that we can expect many cluster admin will try to do in the next
> few months...
>
>
> We ourselves plan to upgrade a small Lustre (production) system from
> 2.12.9 to 2.15.3 in the next couple of weeks...
>
>
> After seeing problems reports like this we start feeling a bit nervous...
>
>
> The documentation for doing this major update appears to me as not very
> specific...
>
>
> In this document for example,
> https://doc.lustre.org/lustre_manual.xhtml#upgradinglustre , the update
> process appears not so difficult and there is no mention of using "tunefs.lustre
> --writeconf" for this kind of update.
>
>
> Or am I missing something ?
>
>
> Thanks in advance for providing more tips for this kind of update.
>
>
> Martin Audet
> ------------------------------
> *From:* lustre-discuss <lustre-discuss-bounces at lists.lustre.org> on
> behalf of Tung-Han Hsieh via lustre-discuss <
> lustre-discuss at lists.lustre.org>
> *Sent:* September 23, 2023 2:20 PM
> *To:* lustre-discuss at lists.lustre.org
> *Subject:* [lustre-discuss] Cannot mount MDT after upgrading from Lustre
> 2.12.6 to 2.15.3
>
>
> ****Attention*** This email originated from outside of the NRC.
> ***Attention*** Ce courriel provient de l'extérieur du CNRC.*
> Dear All,
>
> Today we tried to upgrade Lustre file system from version 2.12.6 to
> 2.15.3. But after the work, we cannot mount MDT successfully. Our MDT is
> ldiskfs backend. The procedure of upgrade is
>
> 1. Install the new version of e2fsprogs-1.47.0
> 2. Install Lustre-2.15.3
> 3. After reboot, run: tunefs.lustre --writeconf /dev/md0
>
> Then when mounting MDT, we got the error message in dmesg:
>
> ===========================================================
> [11662.434724] LDISKFS-fs (md0): mounted filesystem with ordered data
> mode. Opts: user_xattr,errors=remount-ro,no_mbcache,nodelalloc
> [11662.584593] Lustre: 3440:0:(scrub.c:189:scrub_file_load())
> chome-MDT0000: reset scrub OI count for format change (LU-16655)
> [11666.036253] Lustre: MGS: Logs for fs chome were removed by user
> request.  All servers must be restarted in order to regenerate the logs: rc
> = 0
> [11666.523144] Lustre: chome-MDT0000: Imperative Recovery not enabled,
> recovery window 300-900
> [11666.594098] LustreError: 3440:0:(mdd_device.c:1355:mdd_prepare())
> chome-MDD0000: get default LMV of root failed: rc = -2
> [11666.594291] LustreError:
> 3440:0:(obd_mount_server.c:2027:server_fill_super()) Unable to start
> targets: -2
> [11666.594951] Lustre: Failing over chome-MDT0000
> [11672.868438] Lustre: 3440:0:(client.c:2295:ptlrpc_expire_one_request())
> @@@ Request sent has timed out for slow reply: [sent 1695492248/real
> 1695492248]  req at 000000005dfd9b53 x1777852464760768/t0(0)
> o251->MGC192.168.32.240 at o2ib@0 at lo:26/25 lens 224/224 e 0 to 1 dl
> 1695492254 ref 2 fl Rpc:XNQr/0/ffffffff rc 0/-1 job:''
> [11672.925905] Lustre: server umount chome-MDT0000 complete
> [11672.926036] LustreError: 3440:0:(super25.c:183:lustre_fill_super())
> llite: Unable to mount <unknown>: rc = -2
> [11872.893970] LDISKFS-fs (md0): mounted filesystem with ordered data
> mode. Opts: (null)
> ============================================================
>
> Could anyone help to solve this problem ? Sorry that it is really urgent.
>
> Thank you very much.
>
> T.H.Hsieh
>
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