[OpenAFS] Re: Reducing cache scan time

Edgecombe, Jason jwedgeco@uncc.edu
Thu, 27 Jan 2011 10:50:39 -0500

I hard-coded the chunk size for all of my machines because I thought the =
default was 16. 16 is what is mentioned for a disk scan in the afsd =
manpage. I hadn't heard about autotuning the chunksize before. A =
chunksize of 18 (256KB seemed like a good value when I configured my =

If I increase the chunksize of let it default to 20, will that result in =
fewer cache files and a faster cache scan?

What is the algorithm for auto-tuning the chunksize, or where can I find =

Is there a way to measure how effective the chunksize is on a live =


Jason Edgecombe | Linux and Solaris Administrator
UNC Charlotte | The William States Lee College of Engineering
9201 University City Blvd. | Charlotte, NC 28223-0001
Phone: 704-687-3514
jwedgeco@uncc.edu | http://coe.uncc.edu
If you are not the intended recipient of this transmission or a person =
responsible for delivering it to the intended recipient, any disclosure, =
copying, distribution, or other use of any of the information in this =
transmission is strictly prohibited. If you have received this =
transmission in error, please notify me immediately by reply e-mail or =
by telephone at 704-687-3514.=A0 Thank you.

-----Original Message-----
From: openafs-info-admin@openafs.org =
[mailto:openafs-info-admin@openafs.org] On Behalf Of Andrew Deason
Sent: Wednesday, January 26, 2011 4:42 PM
To: openafs-info@openafs.org
Subject: [OpenAFS] Re: Reducing cache scan time

On Wed, 26 Jan 2011 15:58:30 -0500
"Edgecombe, Jason" <jwedgeco@uncc.edu> wrote:

> My afsd options are "-fakestat -dynroot -chunksize 18 -stat 500000
> -daemons 16 -volumes 2000 -blocks 59535014 . I dynamically add the =
> option based on the size of the cache partition.

Any particular reason for the "-chunksize 18" ? That should default to
20 for a cache of that size, which normally I think you'd want.
Increasing it further may help, as it should result in fewer cache

You can tweak the -files argument directly, which should affect the
cache scan (if you start afsd with -verbose, it will tell you what it
defaulted to with "cacheFiles autotuned to X"). But that could affect
cache performance after you start, since that dictates how many chunks
you can store in the cache.

Andrew Deason

OpenAFS-info mailing list