RE: [SQU] squid recommended cache and directory size - cache_dir

Hi,

On Wed, 4 Oct 2000, Lee, Ethan wrote:

> thanks for your reply. In this case are u saying for 18GB, i would hv 36 (or
> more) L1 directory but same 256 L2 directory ie. L2 remains unchanged ? how
> would i verify that this is optimum performance.

As Henrik said, the 256 is chosen as the optimum value for L2 since it is
(approximately) how many directory entries fit in one disk block. That's
why L2 is 256 and every L2 directory contains 256 files. On Linux systems
254 is apparently a better number.

For an 18GB partition I would aim at filling about 80-90% of that with
cache leaving room for people to download big objects (eg CD images) which
squid seems to cache fully before discarding after the session ends.

Let's say we allow 16GB and use the default average object size
(store_avg_object_size) of 13kbytes.

You have 16 * 1024 * 1024 = 16,777,216 kbytes of storage available. That
can hold 1,290,555.1 objects of 13kbytes size. With 256 L2 directories and
256 files per directory you need 19.692308 L1 directories. So you could
get away with say L1 = 20. (20 * 256 * 256 * 13 * 1024 = 16.25Gbytes)

My cache sits on about 9.5kbytes as average size. This means I am using
9/13ths of the space usable. I don't know what is "normal" for avarage
object size but you'll be on the safe side using 13kbytes.

I hope

a) this helps
b) someone will corect me if I am wrong.

Colin

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