(Illustration by Gaich Muramatsu)
On Tue, Aug 31, 2004 at 04:00:21PM -0400, Jan Harkes wrote: > On Tue, Aug 31, 2004 at 02:02:40PM -0500, Troy Benjegerdes wrote: > > I noticed this on linux-kernel, and it looks very interesting... what > > does anyone think of the idea of trying to use cacheFS for the coda > > cache backing store? > > I am not sure about persistency across reboots. Also it assumes that the > cache is completely managed by some an in-kernel filesystem. So we would > need a lot of hooks and changes before venus can put anything in there. > It also makes its own decisions on when to purge objects from the cache, > probably not such a big problem. I don't know how it deals with writes, > it could very well be write-through only and assumes that anything in > the cache can be thrown out at any time without losing data. Cachefs is persistent across reboots. As for the other questions, I'm guessing dhowells has a better answer than I. > It was probably designed for an NFS-like client that is completely in > the kernel and caches on a page granularity. The last time I checked > David Howells' AFS client was an NFS client that happened to use > AFS-compatible rpc calls to talk to the server. But that was a while ago > so I'm not sure if it has changed much since then. > > In any case, I believe even if it is useful, we will still need our own > cache for the metadata and directories and probably for local mutations > that are waiting to be reintegrated. But on the other hand, it could rid > venus from the day-to-day cache-management details and let venus focus > on a smaller variable size cache that only deals with metadata and a > CML. And yes, without restructuring the linux and other platforms would > diverge considerable and make it a big pain to maintain. I suppose the question is would it be worth the pain to maintain if it allowed coda to do partial file caching (or at least allow a reader to start reading a file while it's still being fetched), without introducing all that complexity into venus. My initial reaction is the existing cachefs support for files with holes could be used with a couple of hooks to request more of the file from venus.Received on 2004-08-31 16:49:32