km@mathcs.emory.edu (Ken Mandelberg) (04/10/91)
Does anyone make a CD-ROM Jukebox and software to make the device available
as a network device via NFS?
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Ken Mandelberg | km@mathcs.emory.edu PREFERRED
Emory University | {rutgers,gatech}!emory!km UUCP
Dept of Math and CS | km@emory.bitnet NON-DOMAIN BITNET
Atlanta, GA 30322 | Phone: Voice (404) 727-7963, FAX 727-5611raj@hpindwa.cup.hp.com (Rick Jones) (04/12/91)
There are lots (?) of CD rom jukeboxes out there. However ;-) They all (?) have platter change times measured in *seconds*. This isn't such a big deal when you access the device locally - you wait for as long as it takes for the data to come in. With NFS, things are a bit more impatient shall we say ;-) Being an application written on top of an 'unreliable' network, it retransmits and other fun things. What does this mean? Well, unless you go out there and manually diddle with the NFS/RPC retransmission timers (can one do that 'easily, or does it require adb?), you will have all you clients sending-in umpteen duplicate requests when they weren't needed. NFS is 'tuned' (if one can really say such a thing) for LAN - ie 'fast' access times. In a sufficiently large scenario, you might even achieve congestive collapse of the network with your jukebox spending 99% of its time changing platters ;-( rick jones
emv@ox.com (Ed Vielmetti) (04/13/91)
In article <36530003@hpindwa.cup.hp.com> raj@hpindwa.cup.hp.com (Rick Jones) writes:
They all (?) have platter change times measured in *seconds*. This
isn't such a big deal when you access the device locally - you wait
for as long as it takes for the data to come in. With NFS, things are
a bit more impatient shall we say ;-) Being an application written on
top of an 'unreliable' network, it retransmits and other fun things.
I suspect that a cd-rom jukebox would be much more palatable with a
filesystem like Transarc's AFS in front of it. Stick a single
ordinary magnetic rotating disk as a cache in front of all of the CD
ROMs, and you should get reasonable performance if the locality of
reference patterns allow it.
a lot will depend on reference access patterns, the size of the files,
the amount of cache, etc. opens for files which are not in the cache
are still going to be slow, but it should work out to be better
overall than just a pure NFS setup.
disclaimer: i don't work for Transarc, but I know people who are
working on AFS here at Michigan.
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