Coda File System

Re: sizing and venus memory usage questions

From: Jan Harkes <>
Date: Sat, 17 Jun 2000 19:12:53 -0400
On Sat, Jun 17, 2000 at 09:39:48AM -0500, Dr. Douglas C. MacKenzie wrote:
> After experimenting with different venus cache sizes, I'm surprised at the
> amount of memory venus uses.  My numbers (the server is set for 1.1Gig):
>     Venus cache size (in vstab)          Venus memory usage (from top)
>          50Meg                                             9.9Meg
>        100Meg                                              16Meg
>        500Meg                                              66Meg
>      1000Meg                                            125Meg
> Memory usage seems to run 12 to 15 percent of the cache size,
> which seems pretty high to me.  Am I doing something wrong?

That is probably not the RSS, but the total size which includes the size
of the memory mapped RVM data. There is a `magical' formula which
attempts to estimate how much RVM would be required to support a
specific cache.

This formula is based on assumptions like average filesize to calculate
the # of filesystem objects, number of objects per volume, average
directory size, etc. When the average filesize is much different from
the estimate the RVM size is often not used that much.

> I believe that the cache size is the total disk space available to
> coda for local storage of the hoard files and the current working set,
> so it seems like it should be at least 500Meg to keep network traffic down.
> Does that seem reasonable?

I've been using a 100MB cache for a while, and know that around 200 to
250MB cachesizes there are noticable slowdowns during a hoardwalk that
are caused by inefficiencies in the rebinding of hoard entries to
hoarded files.

> What would I have to do to create a configuration table for the init scripts
> for a 9.9Gig setup (since you already have a 3.3, 9.9 seems like a good
> choice)?

It really depends a lot on how large your files will be. Our current
(outdated) estimates are that with 16KB average filesize the size of
the required RVM data on the server would end up between 2 and 5% of the
exported diskspace. So a 10GB server would need something between 200
and 500MB of RVM data.

Ofcourse with on average 100MB files there is less metadata and the
required RVM data would also be a lot smaller.

Received on 2000-06-17 19:13:36