JUFS update, and questions.

Julian Elischer julian at elischer.org
Wed Mar 10 15:54:50 PST 2004

On 10 Mar 2004, David E. Cross wrote:

> Journaled UFS Technology Description
[... much good stuff deleted]

Not requests for features, just requests as to whether you have
considerred these..

Does it have the ability to keep the journal on a separate media?

I have sometimes seen the ability to have a separate journal disk used
to good effect. (not a system filesystem, but a journalled database).

Having a separate journal file/disk elsewhere can speed things up by
reducing seeks (and other resiliance advantages).
I have also seen double logging and remote logging... each of which of
course has advantages and disadvantages..

Remote logging allows the log to be "replayed" at real time in teh
remote site, leading to an instantaneously correct remote
backup/mirror of the local disk. (of course it can not be safely
accessed except with special safety requirements.. (e.g ability
to shoot an open vnode if teh inode under it is rewritten)

I notice also that you store pre/post stuff and wonder if this can be
used in conjunction with soft-update's need to sometimes roll-back
things on the disk?


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