Can ANYONE see a reason for Network Block Devices to be allowable as
anything other than a module? I can't even get a good idea of what
they're
used for, as it specifically states that you can use NFS/Coda/et al
without it.
--
George Metz
Commercial Routing Engineer
[EMAIL PROTECTED]
http://www2.linuxjournal.com/lj-issues/issue73/3778.html
Given the slightly chequered history of NFS in Linux, it may be deemed
something of an advantage that the NBD driver requires no NFS code in order
to supply a networked file system. (The speed of NFS in the 2.2.x kernels is
markedly superior to that of the 2.0.x implementations, perhaps by a factor
of two, and it no longer seems to suffer from nonlinear slowdown with
respect to size of transfer.) The driver has no file system code at all. An
NBD can be mounted as native EXT2, FAT, XFS or however the remote resource
happens to be formatted. It benefits in performance from the buffering
present in the Linux block device layers. If the server is serving from an
asynchronous file system and not a raw physical device at the other end,
benefits from buffering accrue at both ends of the connection. Buffering
speeds up reads one hundred times in streaming measurements (it reads the
same source twice) depending on conditions such as read-ahead and CPU
loading, and appears to speed up writes approximately two times. With our
experimental drivers, we see raw writes in ``normal use'' achieving about
5MBps to 6MBps over switched duplex 100BT networks through 3c905 network
cards. (The quoted 5-6MBps is achieved with buffering at both ends and
transfers of about 16MB or 25% of installed RAM, so that buffering is
effective but not dominant.)
Additional:
http://atrey.karlin.mff.cuni.cz/~pavel/nbd/nbd.html
http://sites.netscape.net/sebtomac/nbd/nbdd.html
This article seems to indicate that NBD is obsoleted, but I am unable to
determine at a cursory glance if this is the same NBD as the one you are
talking about.
google search words: Network Block Devices AND linux
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