Does FreeBSD 13 disable the VEV cache in ZFS ?
Pete French
petefrench at ingresso.co.uk
Fri May 14 12:34:54 UTC 2021
> Could you check the values of the following sysctl variables:
>
> vfs.zfs.vdev.cache_size
> vfs.zfs.vdev.cache_bshift
> vfs.zfs.vdev.cache_max
> kstat.zfs.misc.vdev_cache_stats.misses
> kstat.zfs.misc.vdev_cache_stats.hits
> kstat.zfs.misc.vdev_cache_stats.delegations
As predicted, all zero, apart from bshift which is 16 and max which is 16384
> https://openzfs.github.io/openzfs-docs/Performance%20and%20Tuning/Module%20Parameters.html#zfs-vdev-cache-size
>
> Quote:
>
> Note: with the current ZFS code, the vdev cache is not helpful and in some
> cases actually harmful. Thus it is disabled by setting the zfs_vdev_cache_size = 0
Ah, thats the thing I should have found msyelf I guess! :-) Actually, if smarter
people than me think that its not useful on OpenZFS, then I shall probably
leave it disabled. Generally people have a good reason for doing things.
I shall have a read,and thankyou for confirming this (and thankyou for
maintinaing zfs-stats! which is an invalauble tool I have found over the years)
-pete.
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