Date: Fri, 14 May 2021 13:34:52 +0100 From: Pete French <petefrench@ingresso.co.uk> To: petefrench@ingresso.co.uk, se@freebsd.org Cc: stable@freebsd.org Subject: Re: Does FreeBSD 13 disable the VEV cache in ZFS ? Message-ID: <E1lhX1o-0009TN-A3@dilbert.ingresso.co.uk> In-Reply-To: <44b0243a-45b6-d098-948b-a6f3d6a53ba7@freebsd.org>
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> 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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