[OpenAFS] 1.3.x memcache performance

[Andrej Filipcic]

On Monday 27 December 2004 17:39, Kris Van Hees wrote:
> 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).

No such tuning. I wanted to know why memcache client was so slow as compared 
to diskcache (kde login to afs home, untar, ...) when the disk load on the 
server was very high. The default memcache settings are obviously not too 
usefull...

Andrej