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SubjectRe: Of Removable Media
Dale Amon (amon@vnl.com) wrote :

[ snip ]

> It is a basic fact of life in a high performance
> file system that data is not written when you
> write to the file, it is written when something
> occurs to flush it to the media. I believe DOS
> wrote immediately and thus got around the problem.
> But floppies are slow, so you take a big performance
> hit for working directly with the media rather than
> a buffer.

Write-back with a short delay :
- no delays to the application
- ( almost ) immediate write to the physical media


> If you take an unsynced diskette out, it may not
> only have blocks not written, it may have the
> entire directory in a bad state.

OS never leaves the the medium unsynced :
- if there are dirty buffers , keep on flushing them.
This should not cause performance problems , because
it happens "in the background" , except if it is a hardware
problem , but IMO PC HW can have a floppy working with no
big impact on the rest of the system

[ 'NeXT sux' snipped ]

> I have a very low level of faith that systems like
> this can be made to work. Even if you have multiple
> disks and keep track of which is in, the disks will
> all be effectively corrupted unless loaded and synced
> before rebooting the computer or using the diskette
> elsewhere.

Solution : "uncorrupt" and sync the diskette before the LED goes
out.

--
David Balazic

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