what if? or combining different ideas j. f. pâris
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![Page 1: What if? or Combining different ideas J. F. Pâris](https://reader036.vdocuments.net/reader036/viewer/2022082506/5697c00f1a28abf838cca69e/html5/thumbnails/1.jpg)
What if?orCombining different ideas
J. F. Pâris
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Combining RAID-5 and LFS
RAID-5allows parallel writes thus increasing I/O
bandwidthhas problems with small writes
LFSensures that all writes are sequentialadds I/O overhead for segment cleaning
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Combining RAID-5 and LFS
What would be the main advantage?
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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
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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 secondsDuring that time it does not need to
revalidate its cache contents sends its updates to the server
unless it has no local disk
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Adding leases to NFS
What would be the main advantage of this approach?
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Adding leases to NFS
What would be the main advantage of this approach? A big reduction of revalidation traffic:
Server could handle more clients
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Adding leases to NFS
Would it not make the server stateful?
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Adding leases to NFS
Would it not make the server stateful?Yes
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Adding leases to NFS
Would it not complicate server recovery?
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Adding leases to NFS
Would it not complicate server recovery?NO, because the state information would
only consist of short lived leasesA server recovering after a crash will
never have to deal with unexpired leases
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Adding leases to NFS
What would you do when a lease is broken?
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Adding leases to NFS
What would you do when a lease is broken?It would mean that somebody else is
accessing the fileWe could either
Return to standard NFS operation with more frequent cache refreshes
Disable client caching for a while
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Adding leases to AFS/Coda
What would be the main advantage of this approach?
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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
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Adding leases to AFS/Coda
What would be the main disadvantage of this approach?
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Adding leases to AFS/Coda
What would be the main disadvantage of this approach?Leases would have to be renewed quite
frequently