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SubjectRe: Volume Managers in Linux
Hi all

all this discussion of volume managers, RAID, and
similar technologies, has revived some thinking I
did a while ago w.r.t.s solving some of this stuff.

Which problems are we exactly trying to solve ?

(1) Adding/removal of disks/partitions from filesystems.
(2) Not having to partition the same physical
disk to accomplish swapping and raw device
access for database et.al.

I can't help with the first problem, but maybe with the
second. VMS has an IO system that solves this reasonably
well. It allows you to create CONTIGUOUS files that can
be directly accessed (called logical IO under VMS). These
accesses are uncached (databases can implement their
own buffering strategies), bypass major chunks of the
filesystem code (speed) and yet accesses are limited to
the blocks that file occupies (prevents the app from
writing elsewhere on the disk).

Obviously this isn't easy and relies on a defragger
to create the necessary space on the disk, but it
works well under VMS and means that I never
have to partition my disks (not even sure if it's
possible :-)

Cheers,
Noel


------------------------------------------------------------
Noel Grandin, Telkom SA, Programmer/Analyst
grandinj@telkom.co.za
























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