big flash disks?

Jamie Lokier jamie at
Mon Jun 2 06:41:06 EDT 2008

Jörn Engel wrote:
> Basically they create a log-structured block device.  For a while I've
> been thinking of doing the same, essentially strip logfs down to a
> single file, which gets a block device interface.  Removing all the
> filesystem complexities (atomic create/unlink/rename, interactions with
> vfs and mm, etc.) makes the project a _lot_ simpler.  I'm nor surprised
> they have a usable product already.
> I decided against it, because I don't believe it to be the best approach
> long-term.  One of the disadvantages is that block devices have
> relatively little knowledge about caching constraints.  A filesystem can
> easily have gigabytes of dirty data around, where a block device is
> expected to return success for every single write in a reasonable
> timeframe, usually measures in milliseconds.

Won't you get essentially the same by creating a single file on LogFS,
and using it for a loopback mount?

Sure, it's more complicated under the hood than a stripped-down LogFS,
but will it behave and perform similarly?

-- Jamie

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