Re: embedded pgsql media-failure

On Tue, Feb 03, 2009 at 12:03:11PM +0100, Kokas Zsolt wrote:
> The businees's side wants to make it as secure as it is possible,
> meaning, that the CF card will have two partitions, and the DB should
> be mirrored or distributed somehow on this two partiton, in case of a
> one-point disk-error the system should stay stable.

As Thomas said, I'd recommend leaving this disk level stuff to the
OS. Divide the CF card in two and create a RAID1 array over the two
partitions. The OS should be able to deal with disk issues much more
robustly than PG. If you were more or less worried about things I
suppose you could divide the disk up further to add more tolerance
(i.e. protect "very important" areas by triple or quadruple redundancy,
bearing in mind that write performance will be reduced by a similar
factor).

I'm not sure if you're trying to solve the wrong problem though, flash
file systems should be used to dealing with this sort of issue and
would be in a position to provide much more useful mechanisms than just
duplicating everything. I've got (second-hand) recommendations of
YAFFS, and have heard good things about JFFS2 as well.

Also, it sounds as though PG may be overkill for this sort of scenario,
it tends to be pretty write heavy which is something you probably don't
want to be doing too much of on a flash device. Have you looked at
anything simpler, maybe sqllite?

Sam