[OpenAFS-devel] fileserver profiling

[Jeffrey Hutzelman]

On Monday, March 14, 2005 07:28:54 AM -0500 chas williams - CONTRACTOR 
<chas@cmf.nrl.navy.mil> wrote:

> In message <20050314040142.GN9768@kalmia.hozed.org>,Troy Benjegerdes
> writes:
>> I just switched to a 100mb cache, (previously it was 1GB), and ran afsd
>> with "afsd -memcache -chunksize 16", and now I'm getting a better, but
>> not optimal throughput of around 25MB/sec.
>>
>> (Out of curiosity, what cache sizes do people generally run at?)
>
> generally speaking memcache is going to be faster

... but less storage-efficient

a 1GB disk-cache will store considerably more than a 1GB memcache, unless 
the chunksize is no larger than 1K.


> increasing chunksize is always going to help with larger files.

True.  This is because the cache manager makes one RPC to fetch each chunk, 
so with larger chunks it is fetching more data per RPC.  This matters 
because under normal usage, the call to read the next chunk is not started 
until the call to read the current chunk completes, so there is no 
streaming across chunks.

-- Jeff