Re: [PATCH] LogFS take three

Bill Davidsen
2007-05-19T15:19:02Z

Dongjun Shin wrote:

> There are so many flash-based storage and some disposable storages,
> as you pointed out, have poor quality. I think it's mainly because these
> are not designed for good quality, but for lowering the price.
>
The reliability seems to be appropriate to the common use. I'm doubious
that computer storage was a big design factor until the last few years.
A good argument for buying large sizes, they are more likely to be
recent design.

> These kind of devices are not ready for things like power failure because
> their use case is far from that. For example, removing flash card
> while taking pictures using digital camera is not a common use case.
> (there should be a written notice that this kind of action is against
> the warranty)
>
They do well in such use, if you equate battery death to pulling the
card (it may not be). I have tested that feature and not had a failure
of any but the last item. Clearly not recommended, but sometimes
unplanned needs arise.

> - In contrast to the embedded environment where CPU and flash is directly
> connected, the I/O path between CPU and flash in PC environment is longer.
> The latency for SW handshaking between CPU and flash will also be longer,
> which would make the performance optimization harder.
>
> As I mentioned, some techniques like log-structured filesystem could
> perform generally better on any kind of flash-based storage with FTL.
> Although there are many kinds of FTL, it is commonly true that
> it performs well under workload where sequential write is dominant.
>
> I also expect that FTL for PC environment will have better quality spec
> than the disposable storage.

The recent technology announcements from Intel are encouraging in that
respect.

--
Bill Davidsen <davidsen@tmr.com>
"We have more to fear from the bungling of the incompetent than from
the machinations of the wicked." - from Slashdot