External journal on flash drive

Jure Pečar pegasus at nerv.eu.org
Sun Sep 12 20:48:39 UTC 2004

On Sat, 11 Sep 2004 19:02:39 +0300
Mika Liljeberg <mika.liljeberg at welho.com> wrote:

> 1) Does the journaling code spread write accesses to the journal device
> evenly, as I hope, or are there blocks that are particularly "hot"?
> I.e., do I have to worry about the flash device dying quickly because of
> frequent erase/rewrite cycles to a small number of blocks?

Any smart enough journal device should do this internally. 
Journal, by its nature, is like a circular file. Can't say much about how
are its i/os layed out on disk, but it shouldn't matter really.

> 2) Currently, the main drive seems to spin up within 60 seconds after a
> write access. I would like the checkpointing to occur only when the
> journal device is getting full. How can I tune this?

Check vm.laptop_mode and vm.bdflush sysctl settings or their appropriate
/proc entries and elvtune command.


Jure Pečar

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