What if? or Combining different ideas J. F. Pâris

Combining RAID-5 and LFS RAID-5 allows parallel writes thus increasing I/O bandwidth has problems with small writes LFS ensures that all writes are sequential adds I/O overhead for segment cleaning

Combining RAID-5 and LFS What would be the main advantage?

Combining RAID-5 and LFS What would be the main advantage? It would greatly reduce the small write penalty assuming that we can write the log one stripe at a time Was it already tried? Yes in the Zebra file system

Adding leases to NFS How would it work? When a process does a lookup for a file it gets a lease on that file for up to a few seconds During that time it does not need to revalidate its cache contents sends its updates to the server unless it has no local disk

Adding leases to NFS What would be the main advantage of this approach?

Adding leases to NFS What would be the main advantage of this approach? A big reduction of revalidation traffic: Server could handle more clients

Adding leases to NFS Would it not make the server stateful ?

Adding leases to NFS Would it not make the server stateful ? Yes

Adding leases to NFS Would it not complicate server recovery?

Adding leases to NFS Would it not complicate server recovery? NO, because the state information would only consist of short lived leases A server recovering after a crash will never have to deal with unexpired leases

Adding leases to NFS What would you do when a lease is broken?

Adding leases to NFS What would you do when a lease is broken? It would mean that somebody else is accessing the file We could either Return to standard NFS operation with more frequent cache refreshes Disable client caching for a while

Adding leases to AFS/Coda What would be the main advantage of this approach?

Adding leases to AFS/Coda What would be the main advantage of this approach? No more lost callbacks More faithful implementation of open-to- close semantics

Adding leases to AFS/Coda What would be the main disadvantage of this approach?

Adding leases to AFS/Coda What would be the main disadvantage of this approach? Leases would have to be renewed quite frequently