[Nottingham] Distributed *file* filesystems

[Martin]

Folks,

There is RAID for offering redundancy at the device block level across
multiple disks in one host;

There is DRBD that offers in effect RAID across disks that are on
networked hosts;

What is there for offering redundancy instead at the /file/ level across
multiple hosted /filesystems/ ?... (Instead of the block device level RAID.)


My crazy idea is to have two hosts acting as NAS so that another machine
can mount both of them and automatically have files immediately
replicated across both, but also to allow another few machines to mount
either NAS read-only to read the files...

How best to do that?

I also hope to gain some redundancy in that if one NAS goes offline, the
second can pick up all the read-only mounts.


I've found:

Gluster Storage Platform
http://www.gluster.com/community/documentation/index.php/Gluster_Storage_Platform

Sector/Sphere
http://en.wikipedia.org/wiki/Sector/Sphere


Anyone played with them?

Any thoughts/ideas for redundant operation but at the filesystem level
rather than at the block level?


I've tried DRBD and it works fine, but it is useless for read-only from
the multiple DRBD hosts if you also have live read-writes... You must go
through the one master machine that has the read-write filesystem
mounted on the DRBD device.


Aside: Whilst in FUSE-land, I also stumbled across:

lessfs data deduplication
http://www.lessfs.com/wordpress/?page_id=50

which could be an alternative to "rsync --link-dest=" for hard linking
to previous unchanged copies for saving backups disk space. Anyone tried it?


All on FUSE:
http://fuse.sourceforge.net/


Any comments, thoughts, stories?

Cheers,
Martin

-- 
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Martin Lomas
martin at ml1.co.uk
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