Does DNLC even play a part in ZFS, or are the Docs out of date? "Defines the number of entries in the directory name look-up cache (DNLC). This parameter is used by UFS and NFS to cache elements of path names that have been resolved." No mention of ZFS. Noticed that when discussing that with a customer of mine. The best workload is one that doesn''t read from disk to begin with :-)> For workloads with millions of files (eg large-scale mail servers) you > will need to increase the size of the Directory Name Lookup Cache > (DNLC). By default, it is way too small for such workloads. If the > directory names are in cache, then they do not have to be read from > disk -- a big win. > > You can see how well the DNLC is working by looking at the output of > "vmstat -s" and look for the "total name lookups." You can size DNLC > by tuning the ncsize parameter, but it requires a reboot. See the > Solaris Tunable Parameters Guide for details. > http://docs.sun.com/app/docs/doc/817-0404/chapter2-35?a=view >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.opensolaris.org/pipermail/zfs-discuss/attachments/20090808/6607f64a/attachment.html>
Allen Eastwood wrote:> Does DNLC even play a part in ZFS, or are the Docs out of date? > > "Defines the number of entries in the directory name look-up cache > (DNLC). This parameter is used by UFS and NFS to cache elements of path > names that have been resolved." > > No mention of ZFS. Noticed that when discussing that with a customer of > mine. > > > The best workload is one that doesn''t read from disk to begin with :-) > For workloads with millions of files (eg large-scale mail servers) you > will need to increase the size of the Directory Name Lookup Cache > (DNLC). By default, it is way too small for such workloads. If the > directory names are in cache, then they do not have to be read from > disk -- a big win. > > You can see how well the DNLC is working by looking at the output of > "vmstat -s" and look for the "total name lookups." You can size DNLC > by tuning the ncsize parameter, but it requires a reboot. See the > Solaris Tunable Parameters Guide for details. > http://docs.sun.com/app/docs/doc/817-0404/chapter2-35?a=view > > > ------------------------------------------------------------------------ >Yes, ZFS uses the DNLC as well. -tim