Nicolas Williams wrote: > On Mon, Jul 28, 2008 at 03:39:10PM -0700, Garrett D'Amore wrote: > >> Nicolas Williams wrote: >> >>> On Mon, Jul 28, 2008 at 01:31:51PM -0700, Garrett D'Amore wrote: >>> >>> >>>> I confess that I didn't realize we lacked client side caching in our >>>> NFSv4. I thought client side caching was one of the significant >>>> benefits that NFSv4 brought to the table (mainly to compete with the >>>> likes of AFS and DFS). >>>> >>>> >>> Let's be precise. The NFSv4 client caches plenty, just not on long-term >>> local storage (which is what cachefs was for). >>> >>> >> How much data is cached by NFSv4? With cachefs you could set up >> fairly large (100's or 1000's of MB) local cache, so for data that >> didn't change often you almost never had to go to the network for >> anything (other than a stat()-like check.) >> > > NFSv4's cache is limited by RAM. It goes away on reboot. > > >>> It's a small gap. >>> >>> I think where it really matters one might use ZFS with iSCSI vdevs and a >>> local L2ARC device. >>> >> An interesting idea. I am not too familiar with iSCSI, but don't you >> need an iSCSI target? I'm not sure, is iSCSI seeing deployment outside >> of the data center? (NFS is designed to support concurrent network use >> and reasonably handles multiple "intiators". How does iSCSI deal with >> such a situation?) >> > > Right. If the filesystems in question are read-only I think you can > share a target as read-only to many initiators. > > But you suggested using it in ZFS with a local L2ARC. Unless I've missed something, I don't think you can share devices (iSCSI or not) between different ZFS's on different hosts. Can you?
-Kyle >> It would be nice to see a commitment to closing any remaining gap as >> much as possible, perhaps by further development of NFSv4 -- as others >> have suggested. >> >> As a final note, I do recall that cachefs was supposed to be generic for >> things like cdroms, etc. I do agree with the proposal that cachefs like >> behavior for anything *other than NFS* is probably not terribly interesting. >> > > I don't. cachefs like behaviour could be useful for CIFS as well (and > some day WebDAV too, why not, and maybe the AFS community would use the > infrastructure if available). > > The problem with cachefs is that it needs to be a service provided to > filesystems that filesystems must use explicitly. > > Nico >
