I'm trying to determine the most optimal way to have a single NFS client
copy large numbers (100-1000) of fairly large (1-50M) files from one
location on an file server to another location on the same file server.
There seem to be several API layers which influence this:
1. Number of OS level processes performing the copy in parallel.
2. Record size used buy the C-library read()/write() calls from these
processes.
3. NFS client rsize/wsize settings.
4. Ethernet MTU size.
5. Bandwidth of the ethernet network and switches.
So far we've played around with larger MTU and rsize/wsize settings
without seeing a huge difference. Since we have been using "cp" to
perform (1), we've not tweaked the record size at all at this point.
My suspicion is that we should be carefully coordinating the sizes
specified in for the layers 2, 3 and 4. Perhaps we should be using "dd"
instead of "cp" so we can control the record size being used. Since
the number of permutations of these three settings are large I was
hoping that I might get some advise from this list about a range of
values we should be investigating and any unpleasant interactions
between these levels of settings we should be aware of to narrow our
search. Also, if there are other major factors outside those listed I'd
appreciate being pointed in the right direction.
---
While I'm on the subject, has there been any discussion about adding an
NFS request that would allow copying files from one location to another
on the same NFS server without requiring a round trip to a client? Its
not at all uncommon to need to move data around in this manner and it
seems a huge waste of bandwidth to have to send all this data from the
server to the client just to have the client send the data back
unaltered to a different location. Such a COPY request would be high
level along the lines of RENAME and each server vendor could optimize
this for their particular hardware architecture. For our particular
application, having such a request would make a huge difference in
performance.
--
Jim Callahan - President - Temerity Software <www.temerity.us>
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