How big of I/O's does INND do to CNFS buffers?

Russ Allbery rra at stanford.edu
Wed May 24 21:57:17 UTC 2000


Jaye Mathisen <mrcpu at internetcds.com> writes:

> Looking at seeing what kind of tuning can be done for tweaking
> performance on multiple striped drives for CNFS, or if I should just
> stick a CNFS buffer on each disk, and not worry about striping it.

INN generally writes out an article at a time (and does a bitmap update),
so the writes are a fairly small one to the beginning of the cycbuff that
may be deferred by the operating system since it's normally done through
mmap and a write the size of an article to the cycbuff.  So for the
average article, around 4KB is a good rule of thumb.  For cycbuffs holding
binaries, the writes could be much larger.

> Also, in a metacycbuff, are I/O's done in the order the cycbuffs are
> listed in the metacycbuff definition?

Yup, unless you use the SEQUENTIAL flag, in which case one cycbuff is used
until it's full and then INN moves on to the next one.  (If you have the
spool spread across a bunch of spindles, you generally don't want
SEQUENTIAL; it's mostly useful for a bunch of smaller cycbuffs on one
physical spindle.)

-- 
Russ Allbery (rra at stanford.edu)             <http://www.eyrie.org/~eagle/>



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