>>> "we have no portable means of expressing that exact constraint to the
>>> kernel"
>> Does this mean that specific operating systems have a better way of
>> dealing with this? Which ones and how?
>
> I'm not aware of any that offer a way of expressing "write these
> particular blocks before those particular blocks". It doesn't seem like
> it would require rocket scientists to devise such an API, but no one's
> got round to it yet. Part of the problem is that the issue would have
> to be approached at multiple levels: there is no point in offering an
> OS-level API for this when the hardware underlying the bus-level API
> (IDE) is doing its level best to sabotage the entire semantics.
[sNip]
Actually, NetWare is one OS that does this, and has been doing so
since the 1980s with version 2 (version 6.5 is the current version today).
They have a Patented caching algorithm called "Elevator Seeking" which both
prolongs the life of the drive by reducing wear-and-tear and improving
read/write performance by minimizing seek operations.
With IDE it seems that this caching algorithm is also beneficial, but
it really shines with SCSI drives.
In all my experience, SCSI drives are much faster and far more
reliable than IDE drives. I've always assumed that it boils down to "you
get what you pay for."
--
Randolf Richardson - rr@8x.ca
Inter-Corporate Computer & Network Services, Inc.
Vancouver, British Columbia, Canada
http://www.8x.ca/
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