Re: embedded pgsql media-failure

Kokas Zsolt wrote:
>> I've got (second-hand) recommendations of
>> YAFFS, and have heard good things about JFFS2 as well.
>
> What I see from them is that they supported wear-leveling before
> wear-leveling was included into the drives.

AFAIK jffs2 and yaffs are really for simple (generally memory-mapped)
flash media that doesn't have any wear leveling, block remapping, etc.
Things that're usually found on small embedded systems.

Most flash storage that can be attached to PC-like machines is hidden
behind a hardware translation interface (in the CF/SD/etc card its self
or in the USB/ATA/etc adapter for it) that takes care of wear leveling
and block remapping. That way you can use poorly suited filesystems like
FAT32, ext3, etc on it without it flaking out on you. I haven't
personally seen any that let you bypass or disable that remapping and
address the raw flash. If anyone knows of any, I'd be really interested,
as it'd be very handy for a project I'm working on.

BTW, I'm not sure how much good OS-level RAID on a single device will do
for you. Linux will try to reset the interface to the drive on I/O
errors, will hang for long periods waiting for reads, etc and I wouldn't
be at all surprised if this caused `md' to think that both "devices"
(partitions) were failed. It also won't help you if the card's interface
fails, the CF adapter fails, etc. Surely you'd be better off with *TWO*
CF cards in RAID if you really want redundancy and reliability?

--
Craig Ringer