On Dec 27, 2004, at 6:20 PM, Andrej Filipcic wrote:
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...
That depends on your network, the sizes of your files and the nature of the file access.
But that's always the problem with default values on caches. ;-)
I'm not very sure how fast your AFS client is supposed to be...
Horst
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