[OpenAFS] Re: recommended UFS parameters for cache partition?

[Andrew Deason]

On Mon, 26 Dec 2011 15:16:16 -0500 (EST)
Benjamin Kaduk <kaduk@MIT.EDU> wrote:

> Setting up a new solaris machine, I've gone and partitioned the disk,
> giving about 9GB to the cache partition.  But now I need to put a
> (UFS) filesystem on it, and I wondered -- should I be tweaking the UFS
> parameters for the CM's workload?  It seems like the filesystem's
> structure is pretty well-determined, with a bunch of chunksize (?)
> files, the number of which is determined by the arguments to afsd.

Well, those are maximums; you may have many files that are smaller than
the chunksize and you will probably have many cache files not in use.
Furthermore, while the file structure may be known and dependant on the
chunk size, the I/O patterns are not. An application write() will
generally involve a write()-equivalent to the cache backing file. An
application read() will result in chunksize-sized writes to the cache
files, but they are done in write()s in 4k chunks, iirc.

> So, if I know what my afsd settings are, how does that translate to an
> optimal UFS layout?  (Or should I just not worry about it and assume
> that any potential improvements would be lost in the noise?)

I wouldn't expect the ufs settings to make a noticeable difference, but
I haven't ever looked at it seriously (I don't think I've ever talked to
somebody that seemed particularly concerned about it).

-- 
Andrew Deason
adeason@sinenomine.net