(Illustration by Gaich Muramatsu)
Hi! On Tue, 9 Oct 2001 15:30:14 -0400 Jan Harkes <jaharkes_at_cs.cmu.edu> wrote: > On Tue, Oct 09, 2001 at 11:53:09AM +0200, Ren? Rebe wrote: [...] > It will be extremely fast when they are already in the cache. How do you > expect work with a file while disconnected from the network if you only > have a random few bits and piece cached locally, and then when both the > local and the server version of the file are updated, how would you > reconstruct a consistent complete version of the local copy. > > Also, if you want to work with file-chunks, we suddenly would need to > make more upcalls from the kernel to userspace when a file is accessed > to check whether the stuff is present. Upcalls are pretty expensive, > just compare creating 100 files in /coda compared to creating 100 files > on the local disk. (while Coda is write-disconnected, otherwise you're > measuring client-server communication overhead). Shure. Dealing with file-chunks would be difficult and wouldn't leave bits for the disconnected-mode. But I wouldn't need to have such big files in my local cache. Since copying would be painfull slow (open () a uncached 600MB file over 100MBit ethernet would take 600/12.5MB/s -> at least 48 seconds :-((. It would be nice to have a size-threshold for cached files ... BTW: Is my assumption "that CODA can only handle files if they completely fit into the available cache-space" correct? > Partial caching just won't work if you want to have any guarantees on > consistency, just look at the mess AFS3 made of it. Small example for > AFS users, open a file for read/write, write 100KB, sleep for a bit. In > the mean time, truncate the file and write a few bytes of data from > another client. Then continue writing on the first client. You end up > with... The few bytes written by the second client, almost 64KB of 0's, > and then the tail of the file as written by the first client. Similar > things apply to NFS which basically caches on a page basis, and earlier > writes can possibly replace more recent updates. Just google for the > horror stories. None of the two major Linux NFS solution works for me without corruptions ... - although I do not see that any bits are cached ... :-( > > In one docu I found that the cache shouldn't be larger than ~300MB. Is this > > the latest info? Especially for the larger files (mentioned above) and hording > > on my laptop this would not be that cool ... > > That is derived from on an average file size of 24KB, i.e. we're really > concerned about the number of cacheable files. 300MB is approximately > 12000/13000 cacheable files. If your files are on average 600MB, the > cachesize can be several terabytes (never tried, but...) as long as you > override the default calculation by defining values for both cacheblocks > _and_ cachefiles in /etc/coda/venus.conf. I'll test it the next days. > the reply-to address. Mutt typically handles this stuff pretty well, so > I expect it is some override to avoid breaking standards. :-( OK. fixed. > Jan Very much thanks for the reply! -- eMail: rene.rene_at_gmx.net rene.rebe_at_rocklinux.org Homepage: http://www.rene.rebe.myokay.net/ Anyone sending unwanted advertising e-mail to this address will be charged $25 for network traffic and computing time. By extracting my address from this message or its header, you agree to these terms.Received on 2001-10-09 17:35:24