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Does DNLC even play a part in ZFS, or are the Docs out of date?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
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Yes, ZFS uses the DNLC as well.
-tim
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