search

openzfs / zfs

OpenZFS on Linux and FreeBSD
https://openzfs.github.io/openzfs-docs
Other
10.68k stars 1.76k forks source link

arcstat and arc_summary report impossible value for L2 cache size #16792

Open clhedrick opened 4 days ago

clhedrick commented 4 days ago

System information

Type Version/Name
Distribution Name Ubuntu
Distribution Version 22.04
Kernel Version 6.6.44
Architecture x64
OpenZFS Version 2.2.6

Describe the problem you're observing

arc_summary shows

L2ARC size (adaptive): 44.5 TiB Compressed: 12.5 % 5.6 TiB Header size: 0.1 % 33.1 GiB MFU allocated size: 10.5 % 601.1 GiB MRU allocated size: 89.4 % 5.0 TiB Prefetch allocated size: 0.1 % 7.1 GiB Data (buffer content) allocated size: 100.1 % 5.6 TiB Metadata (buffer content) allocated size: < 0.1 % 214.9 MiB

We have a little under 6 TB of disk assigned, so the 44 TB size seems impossible.

Looking at the last few months, I see values as high as 85 TB.

The same data appears in arcstat.

Describe how to reproduce the problem

n.a

Include any warning/errors/backtraces from the system logs

imwhocodes commented 4 days ago

I'm not a dev but as far I understand OpenZFS you have a lot of highly compressible data, the actual on-disk-size of L2ARC is around 5.6TB (second line) that when decompressed will inflate to 44TB