> However, I want to ask, is there _any need_ to implement "Thin
A good question
Except that you can run out of space and die.
A cluster file system can do cache management and in theory snapshots.
The iscsi larget is a block property - the equivalence in fs layer would
I guess be NFS. Most of those have been developed too ;)
Some storage vendors do the most marvellously bizzare things. That
doesn't mean they are right answers. EMC don't/didn't have a cluster file
system so that rather limited their choice.
I think you missed one however and maybe one EMC considered - its a much
easier way to do cross platform non shared filestore as a device than add
clustering file systems to do that.
However if you overcommit you have a problem. Its interesting as a front
end technology with an array of slow large disks behind it (so you don't
overcommit but push old storage to the slow disks). I don't think its
interesting in the general case except where you can carefully avoid
overcommit by management policies.
Its also not helped by the fact your storage layer needs to understand
the fs's it supports in order to deduce what blocks are free so that it
can recover them.
Alan
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