On Sat, 3 Apr 2010 17:02:38 +0400 Raghavendra G <raghavendra@xxxxxxxxxxx> wrote: > On Fri, Apr 2, 2010 at 5:49 PM, Stephan von Krawczynski <skraw@xxxxxxxxxx>wrote: > > > On Fri, 02 Apr 2010 14:41:36 +0100 > > Gordan Bobic <gordan@xxxxxxxxxx> wrote: > > > > > On 02/04/2010 12:32, Olivier Le Cam wrote: > > > > > > > Following to a recent talk on the IRC channel, it came to my mind that > > > > caching lookups could (in this particular situation) greatly improve > > the > > > > performances. > > > > > > Maybe some of the devs can explain whether this is plausible, but I > > > somewhat doubt it. You would lose the integrity guarantees. > > > > If you're talking of data integrity here I doubt that it is there at all. > > Yesterday I checked a configuration with 2.0.9 replication and 3 clients > > with > > iocache. I found out that if I edit an ascii file on one client and save it > > back being the same size as before, another client still sees the old file > > content. I checked the servers and found that they all contained the > > correct > > new file version. So the data integrity is broken anyway when using iocache > > on > > clients > > > > This is quite expected, since the client on which the data is being read has > cached the data. io-cache has cache-timeout option which can be tuned to > force the clients to check whether the file has changed on server after > configured time intervals. > > However also please note that, if the file is being modified and read from > the same client, this issue would/should not have happened. To make this point clear: There is no issue modifying and reading a file on the very same client. There is an issue modifying on client1 and reading on client2, and it is not solvable via io-cache options like cache-timeout. As you can see in my previous posts the cache-timeout is set to 1 (second). It is obvious that I was not able to check within one second on two interactive consoles. So I cannot tell you the influence cache-timeout really has, but obviously it does not work as you expected. The io-cache stays active on client2, although being older than 1 second and containing an outdated file content. Even if ls -l already delivers a _new_ file date and _new_ size the file content still may be outdated (an btw not matching the file size in ls). You may call that _broken_. > > > Gordan > -- > Raghavendra G -- Regards, Stephan
