User manual

Setting up iXOS-JUKEMAN
iXOS-JUKEMAN 2.2 User Manual Pre.12/9782
mount -o port=4027,timeo=99,retrans=14,soft
<hostname>:/views_rr /cd
mounts the server’s file system on the empty directory /cd of the client.
Once this is done, all disks appear as subdirectories of /cd. The simple
command ls -l /cd shows a list of all available disks.
Depending on the operating system, some versions of mount require ad-
ditional parameters, e. g.,
mount -F nfs -o port=.. or mount -f NFS,port=…. See man
mount for details.
The port=4027 option tells mount that the NFS server uses port 4027
instead of 2049, which is used by the standard NFS daemon. This en-
ables the server to coexist with the standard nfsd so clients can use both
hard disks and jukeboxes on the server computer concurrently. NT does
not include a standard nfsd; consequently, the NT version uses the stan-
dard port, and you do not need to specify the port number.
For some newer UNIX operating systems like Solaris 2.5, DEC UNIX 4.0
or IRIX 6.4 the mount command should include a further option 'vers=2'.
Without this option NFS version 3 would be used. iXOS-JUKEMAN sup-
ports NFS protocol version 2 only, so that the client would use version 2
anyway after negotiating with the server.
mount -o port=4027,timeo=99,retrans=14,soft,vers=2
host:/views_rr /cd
To understand the other options you need to be familiar with NFS clients:
A user level application accesses a mounted network file system as if it
were any local magnetic disk. The kernel of the client computer automati-
cally generates NFS requests and waits for the answers, which in turn are
used to satisfy the accesses requested by the application. But networks
may drop a request or an answer. Therefore, the NFS client built into the
client’s kernel not only generates NFS requests, but also retransmits them
if it does not receive a reply within a reasonable time.
The timeo=99 option instructs the kernel’s NFS client to retransmit a re-
quest if there is no reply after 99 tenths of a second (9,9 seconds). These
retransmits are not visible to the users, except for messages such as “NFS
server not responding, still trying”. Short time-outs increase
the network load because each disk move can cause several useless re-
transmits. Long time-outs are bad if a packet is dropped by an unreliable
network and a user must wait until the kernel’s NFS client retransmits the
request. After each retransmit, the time-out value is doubled, up to a
maximum of one minute.