On Mon, 18 Sep 2006, Dave Cramer wrote:
> Here's the problem:
>
> Customer needs to be able to just plug, and unplug USB drive WITHOUT
> unmount, or sync.
>
> The drive is being used to log data.
>
> I was thinking about doing write ahead logging, but then it occurs to
> me that the only issue with disk corruption is when re-arranging the
> structure of the disk
>
> ie doing deletes, creating, removing directories
>
> So my idea is to simply create n files named 0001-nnnn where n is the
> size of the flash/size of each file before hand and then simply write
> into those files.
> My expectation is that the worst thing that will happen is I will
> lose one file worth of data if it is pulled out before synching the
> disk.
> I' will also write 0's to the files before putting the data on them.
>
I'm not so sure that precreating the files etc will help. You'd really
need to look at the details of how the particular filesystem you are using
write to and extends files.
Check out the "sync" option to mount - should save you some, though it
hits write performance. Suspect you throughput isn't that great that you'd
worry.
In general there is no 100% solution to this problem. But maybe the data
being collected doesn't merit the hoops you'd have to go thru' to give you
100%
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