Hi,
I have problem with CephFS on writing big size file. I have found that my OpenStack Nova backup was not working after I change the rbd based mount of /var/lib/nova/instances/snapshots to CephFS based (mounted on /etc/fstab on all Nova compute nodes). I couldn't relize the cause until I tried to do some test below.
[root@compute-aa instances]# sudo -S -u nova dd if=/dev/zero of=./snapshots/test/test.dat bs=4096 count=1024
1024+0 records in
1024+0 records out
4194304 bytes (4.2 MB) copied, 0.002956 s, 1.4 GB/s
It seem that making 4.2MB size file is OK. The "test" folder was been created by nova user too.
[root@compute-aa instances]# sudo -S -u nova dd if=/dev/zero of=./snapshots/test/test.dat bs=4096 count=1048576
This test was hang and gave me "D state" of dd process which cannot be killed, so I must reboot that node. This make afraid to do some more test with lower size. When I tried to see the folder content, I found following result.
[root@compute-aa ~]# ls -lah /var/lib/nova/instances/snapshots/test/
total 0
drwxr-xr-x 1 nova nova 0 Aug 24 22:35 .
drwxr-xr-x 1 nova nova 0 Aug 24 22:33 ..
-rw-r--r-- 1 nova nova 0 Aug 24 22:35 test.dat
I prefer to use CephFS since the snapshot folder is only for temporary. Please help me to solve this problem.
Best regards,
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