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On one of the nodes in a kubernetes cluster I observe more than one $MAJ:$MIN device number in the same line of the io.stat file.

I check io.stat inside the pod on this node and there are two MAJ:MIN numbers in the line #4:

# cat /hostfs/sys/fs/cgroup/io.stat
7:8 rbytes=14336 wbytes=0 rios=11 wios=0 dbytes=0 dios=0
253:0 rbytes=1634749952 wbytes=5449465344 rios=38749 wios=399082 dbytes=0 dios=0
9:126 rbytes=16306176 wbytes=0 rios=724 wios=0 dbytes=0 dios=0
9:127 8:16 rbytes=18655744 wbytes=0 rios=967 wios=0 dbytes=0 dios=0
8:0 rbytes=1650753024 wbytes=5449609728 rios=39161 wios=373122 dbytes=0 dios=0
11:0 rbytes=0 wbytes=0 rios=3 wios=0 dbytes=0 dios=0
7:7 rbytes=92527616 wbytes=0 rios=2418 wios=0 dbytes=0 dios=0
7:6 rbytes=484352 wbytes=0 rios=42 wios=0 dbytes=0 dios=0
7:5 rbytes=1259520 wbytes=0 rios=68 wios=0 dbytes=0 dios=0
7:4 rbytes=1225728 wbytes=0 rios=54 wios=0 dbytes=0 dios=0
7:3 rbytes=2302976 wbytes=0 rios=238 wios=0 dbytes=0 dios=0
7:2 rbytes=483328 wbytes=0 rios=42 wios=0 dbytes=0 dios=0
7:1 rbytes=485376 wbytes=0 rios=44 wios=0 dbytes=0 dios=0
7:0 rbytes=499712 wbytes=0 rios=49 wios=0 dbytes=0 dios=0

I assume the issue could be caused by using multi-path option for the attached storage. Is it legit to have multiple MAJ:MIN device numbers in the same line of io.stat?

Vitaly
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  • https://github.com/torvalds/linux/blob/61d325dcbc05d8fef88110d35ef7776f3ac3f68b/block/blk-cgroup.c#L997 I do not really see a way, you would have to follow blkg_dev_name . – KamilCuk Apr 25 '23 at 12:38
  • Thanks, I just try to understand if having more than one dev number in /sys/fs/cgroup/io.stat is a bug or a feature – Vitaly Apr 25 '23 at 12:44

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