nfs options --- plz help

[Maaz]

from nfs man:
timeo=n The value in tenths of a second before sending the first retransmission after an RPC timeout.

I wana know in what scenario/situation an RPC timeout will occur ? Is timeout will occur when nfs server is offline ? or when ? and plz also explain "...first retransmission after an RPC timeout" what retransmission ? I wana know first retransmission of what ?


from nfs man:
intr If an NFS file operation has a major timeout and it is hard mounted, then allow signals to ....

what is hard mounted ?

Thanking in anticipation
Regards
Maaz

[Huc_1 · Accepted solution]

Have a read at the following, it is better explained and in more details then in the man pages.

http://www.tldp.org/HOWTO/NFS-HOWTO/

J-P Huc

[Andrew Cowan]

NFS filesystems can be hard or soft mounted. Hard is considered more secure since the client waits until the host becomes available again following any interruption, whereas as soft simply times-out and aborts the connection. Soft mounts are also interruptable, meaning that if a mount was stuck for some reason you could hit Ctrl-C (or whatever the keystroke is), and the connection attempt would terminate.

[Sergejs Svitnevs]

If the server or network is heavily loaded and the RPC requests are timing out you can try to increase timeo mount option for the directory.

"Common Problems with NFS" document:
http://docs.hp.com/en/B1031-90043/ch07s01.html

Regards,
Sergejs

[Wim Van den Wyngaert]

I just tested it. NFS client sends 7 UDP packets to the port mapper of the server. The 2nd packet is sent after 1 seconds, the packets after this have an increasing time interval (4 seconds at the end).

So, in total, the server has more than 20 seconds to answer. If you increase the timeout, the total delay will increase too (didn't test that).

Note that this is only the case if ARP to the router or node already worked. For the test, I removed the portmapper.

Wim

[Maaz]

Dear J-P Huc , Andrew Cowan, Sergejs Svitnevs, and Wim Van den Wyngaert, I m highly thankful to u all for the support.

One more silly question... diff b/w sync and async ? and their usage ? its also explained in the tutorial, but i want your people's explanation/help for better understand

Thanks and Regards
Maaz

[Steven E. Protter]

sync is a one way or half duplex type operation. You write then you read.

async allows for reading and writing at the same time.

Databases need asynchronous access for performance reasons.

asynch is riskier to data integrity.

SEP