Re: PC--What is it good for?

In rec.arts.sf.written Jasper Janssen <jasper@[EMAIL PROTECTED]
> wrote:
> On Mon, 17 Dec 2007 16:44:56 -0800, archmage@[EMAIL PROTECTED]
 (Nate Edel)
wrote:
> >In rec.arts.sf.written Jasper Janssen <jasper@[EMAIL PROTECTED]
> wrote:
> >> On Thu, 13 Dec 2007 13:35:27 -0800, archmage@[EMAIL PROTECTED]
 (Nate Edel)
wrote:
> >> >Heck, from what I can see, people don't want to even deal with
properly
> >> >stopping external USB devices before unplugging them, and that's no
cash
> >> >cost, just inconvenience.
> >>
> >> And there's no reason whatsoever for it to be necessary, either.
Writeback
> >> versus write-through caching schemes aren't *that* different in
> >> performance, mostly. Most USB sticks and card readers have activity
LEDs,
> >> jsut like floppy drives used to have. Don't pull while light is
fla****ng.
> >
> >Writeback vs. write through makes a huge difference when the issue is
> >batching up metadata writes vs. making everything synchronous.  That's
> >especially true with disk with its big difference in seek time vs.
write
> >throughput, but somewhat noticeable even with flash. 
>
> I'm not sure you should be using an external disk for applications where
> you'd be regularly writing very small chunks of data, anyway. It's not
the
> typical usage scenario for a USB stick, that's for sure. Or at least it
> wasn't prior to U3/****tableApps & co.

Ideally?  Probably not, or at least you should be using a more secure
connector.  Nevertheless, these days it's the most practical backup
mechanism, and the most practical way to move large chunks of data of
whatever sort around.  It's also a lot easier for most people to just plug
in an external drive to increase primary storage than to install a second
internal hard drive (or worse yet, migrate their OS to a new, bigger
primary
drive if their system is a notebook or has a small case.)

It's much less of an issue for flash than for external hard drives, given
the different latency characteristics.  

What do people use these for where small writes can matter?
There's also backing up large numbers of do***ents or image libraries...
heck, at USB2 transfer rates going to a modern disk drive, even doing a
seek
(or two) per 5mb MP3 file to do a metadata write slows things down
noticeably.

Using software which does incremental backups helps; alternatively,
sticking
everything in an archive (zip/rar/tar/7z) helps a lot more... assuming you
create the archive on fast local disk first.  These are plenty
inconvenient
for the average user.

> If the cache is inside the controller on the USB key, it will of course
> light the read/write led while any data is waiting in the cache to be
> written. I don't think there's an API that allows it to do the same for
a
> writeback cache in the PC itself, but it wouldn't be *that* hard to
> implement.

There are a lot of things for filesystems which are easy to implement and
haven't been done; the Windows filesystem implementation (less at the
level
of NTFS than all the caching that happens regardless of the FAT/NTFS
[/HPFS,
on older NT-based OSes]) blows chunks, and can pretty leave things limited
by disk random IO that Linux or any modern Unix (presumably OS X also)
would
have long since gotten into cache.

-- 
Nate Edel                               http://www.cubiclehermit.com/
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