Hi TH,
I think you'll have to set max_create_count=20000 after step 7 unless
you unmount and remount your MDT.
And for step 4, I used conf_param instead of set_param during my drill
and I noticed this might be more resilient if you are using a HA pair
for the MDT because the MDS might try to activate the inactive OST
during failover as set_param is only changing run time option?
Regards,
Angelos
On 05/03/2021 11:48, Tung-Han Hsieh via lustre-discuss wrote:
Dear Hans,
Thank you very much. Replacing the OST is new to me and very very
useful. We will try it next time.
So, according to the description of the manual, to replace the OST
we probably need to:
1. Lock the old OST (e.g., chome-OST0008) such that it will not
create new files (run in the MDT server):
lctl set_param osc.chome-OST0008-osc-MDT0000.max_create_count=0
2. Locate the list of files in the old OST: (e.g., chome-OST0008):
(run in the client):
lfs find --obd chome-OST0008_UUID /home > /tmp/OST0008.txt
3. Migrate the listed files in /tmp/OST0008.txt out of the old OST.
(run in the client).
4. Remove the old OST temporarily (run in the MDT server):
lctl set_param osc.chome-OST0008-osc-MDT0000.active=0
(Note: should use "set_param" instead of "conf_param")
5. Unmount the old OST partition (run in the old OST server)
6. Prepare the new OST for replacement by mkfs.lustre with --replace
option, and set the index to the old OST index (e.g., 0x8):
(run in the new OST server)
mkfs.lustre --ost --mgsnode=XXXXXX --index=0x8 --replace <device_name>
7. Mount the new OST (run in the new OST server).
Best Regards,
T.H.Hsieh
On Thu, Mar 04, 2021 at 04:59:54PM +0100, Hans Henrik Happe via lustre-discuss
wrote:
Hi,
The manual describe this:
https://doc.lustre.org/lustre_manual.xhtml#lustremaint.remove_ost
There is a note telling you that it will still be there, but can be
replaced.
Hope you migrated your data away from the OST also. Otherwise you would
have lost it.
Cheers,
Hans Henrik
On 03.03.2021 11.22, Tung-Han Hsieh via lustre-discuss wrote:
Dear All,
Here is a question about how to remove an OST completely without
restarting the Lustre file system. Our Lustre version is 2.12.6.
We did the following steps to remove the OST:
1. Lock the OST (e.g., chome-OST0008) such that it will not create
new files (run in the MDT server):
lctl set_param osc.chome-OST0008-osc-MDT0000.max_create_count=0
2. Locate the list of files in the target OST: (e.g., chome-OST0008):
(run in the client):
lfs find --obd chome-OST0008_UUID /home
3. Remove OST (run in the MDT server):
lctl conf_param osc.chome-OST0008-osc-MDT0000.active=0
4. Unmount the OST partition (run in the OST server)
After that, the total size of the Lustre file system decreased, and
everything looks fine. However, without restarting (i.e., rebooting
Lustre MDT / OST servers), we still feel that the removed OST is
still exists. For example, in MDT:
# lctl get_param osc.*.active
osc.chome-OST0000-osc-MDT0000.active=1
osc.chome-OST0001-osc-MDT0000.active=1
osc.chome-OST0002-osc-MDT0000.active=1
osc.chome-OST0003-osc-MDT0000.active=1
osc.chome-OST0008-osc-MDT0000.active=0
osc.chome-OST0010-osc-MDT0000.active=1
osc.chome-OST0011-osc-MDT0000.active=1
osc.chome-OST0012-osc-MDT0000.active=1
osc.chome-OST0013-osc-MDT0000.active=1
osc.chome-OST0014-osc-MDT0000.active=1
We still see chome-OST0008. And in dmesg of MDT, we see a lot of:
LustreError: 4313:0:(osp_object.c:594:osp_attr_get())
chome-OST0008-osc-MDT0000:osp_attr_get update error [0x100080000:0x10a54c:0x0]:
rc = -108
In addition, when running LFSCK in the MDT server:
lctl lfsck_start -A
even after all the works of MDT and OST are completed, we still see that
(run in MDT server):
lctl get_param mdd.*.lfsck_layout
the status is not completed:
mdd.chome-MDT0000.lfsck_layout=
name: lfsck_layout
magic: 0xb1732fed
version: 2
status: partial
flags: incomplete
param: all_targets
last_completed_time: 1614762495
time_since_last_completed: 4325 seconds
....
We suspect that the "incomplete" part might due to the already removed
chome-OST0008.
Is there any way to completely remove the chome-OST0008 from the Lustre
file system ? since that OST device has already been reformatted for
other usage.
Thanks very much.
T.H.Hsieh
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