nicc777 <nicc777@gmail.com> said:
>I am rather new to cluster file systems, so let me state my
>requirements, and hopefully the kind people here get point me in the
>right direction.
>
>Basically I want a file system spanning multiple physical hosts, but
>mounted on a server as a single mount point - almost like having some
>kind of RAID over various physical nodes. The idea is that if one node
>fails, the server should still be able to continue with processing
>(assume it's something like a database). I am hoping that when the
>failed file server(s) come back online, the "RAID" should be rebuild
>on the fly, like a real RAID. This will be first prize.

This doesn't sound what commonly is called "cluster file system";
"cluster file system" (to me, at least), means a set of shared storage
accessible by several computers concurrently (as local storage).
So, the actual storage media will be concurrently connected to
several hosts, and all hosts are able to concurrently access the
file system(s) created on the shared media.

What you describe sounds something I've heard Google having developed
for their search data storage - but I haven't heard of such technology
being used anywhere else.

>PS: if anybody knows something about battery backups for hard drives,
>and how to protect the hard drive cache in case of power failures etc,
>I would also like to hear some of your thoughts/learnings/experiences.

There are storage subsystems (disk racks) from various vendors with
various amounts of local battery-backed cache. As long as the write
to the cache completes, the disk subsystem will be in consistent
state (and when the power resumes, will flush any buffered data to
disks).
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