[OpenAFS] 1.3.x memcache performance

[Kris Van Hees]

On Mon, Dec 27, 2004 at 05:28:14PM +0100, Andrej Filipcic wrote:
> > > On gigabit network, the copy speed with memcache is never larger than
> > > 20
> > > mbyte/s, with disk cache it can go up to 70 mbyte/s.
> 
> Well, it is not actually performance. dd if=/dev/zero to afs space transfer  
> reaches something like that. This is of course a peak number. Half of time 
> data is written to a local disk cache with no network activity, so on 
> average, the transfer would be 30-40 MB/s. AFS read speed is between 10-20 
> MB/s. 
> 
> New memcache parameters give similar write transfer now (~60 MB/s on average).

So basically, you are measuring a combination of how fast you can write to
your cache, together with how fast the AFS client can flush the data from
the cache to the server.  Do you have writebehind turned on or off on your
AFS client?  If writebehind is allowed, then you only measure writing to the
cache + part of the flushing to the server (since flushbehind allows the
close() system call to return before the entire file has been flushed to the
server).

	Kris