hard nfs mounts vs. soft nfs mounts

[Susan Harris]

Hi,

In our environment, we have many NFS mounts going every which way. They are all soft mounts. Occasionally, we run into problems, I get msgs. in the syslogs of the nfs clients, "NFS writet failed for server x07:RPC:Timed out". Again, all of these mounts have been set up a soft mounts since the beginning of time. I'm not sure whether a hard mount was considered back then. What would the downside be, going to hard mounts? Any suggestions would be helpful...
Thanks!
Sue
PS. We are running 11.0 on all nfs clients and servers

[Sanjay_6]

Hi Susan,

Maybe these links can help,

http://docs.hp.com/cgi-bin/fsearch/framedisplay?top=/hpux/onlinedocs/B1031-90048/B1031-90048_top.html&con=/hpux/onlinedocs/B1031-90048/00/00/9-con.html&toc=/hpux/onlinedocs/B1031-90048/00/00/9-toc.html&searchterms=hard%20soft%20mount&queryid=20020222-073324

http://docs.hp.com/cgi-bin/fsearch/framedisplay?top=/hpux/onlinedocs/B1031-90048/B1031-90048_top.html&con=/hpux/onlinedocs/B1031-90048/00/00/45-con.html&toc=/hpux/onlinedocs/B1031-90048/00/00/45-toc.html&searchterms=hard%20soft%20mount&queryid=20020222-073324

Hope this helps.

Regds

[Sanjay_6]

Hi Susan,

This is something on the performance,

http://docs.hp.com/hpux/onlinedocs/os/11.0/tuningwp.html#nfs

The above link comes from this doc,

http://docs.hp.com/hpux/onlinedocs/os/11.0/tuningwp.html

Hope this helps.

Regds

[Patrick Wallek]

If you mount with the soft option then you will get errors when an NFS server is not available. If you use the hard option, you won't get the errors, but HP-UX will keep trying to get to the NFS mount until the server responds again or you reboot the client.

From the mount_nfs man page:

soft|hard
Return an error if the server does not respond, or continue the retry request until the server responds. The default value is hard.

Hard vs. Soft
File systems that are mounted read-write or that contain executable files should always be mounted with the hard option. Applications using soft mounted file systems may incur unexpected I/O errors.

To improve NFS read performance, files and file attributes are cached. File modification times get updated whenever a write occurs. However, file access times may be temporarily out-of-date until the cache gets refreshed. The attribute cache retains file attributes on the client. Attributes for a file are assigned a time to be flushed. If the file is modified before the flush time, then the flush time is extended by the time since the last modification (under the assumption that files that changed recently are likely to change soon). There is a minimum and maximum flush time extension for regular files and for directories. Setting actimeo=n sets flush time to n seconds for both regular files and directories.

[G. Vrijhoeven]

Hi,

Soft NFS has one big advantage. If the NFS server is not responding (down) it generates an error instead of waiting indefinitely. The advantage of Hard nfs is is does not require actions on the client side if a nfs server is rebooted.

Hope this will help,

Gideon

[Helen French]

Hi Susan,

The major difference is that the hard mounted nfs file systems will keep waiting for the server to respond and it does not require the client to be restarted, if the server reboots.

In soft mounted, will not wait for indefenite period in case of a server down issue.

Also you can check the man pages of nfs mount ( man 1m mount_nfs) for specific options about the nfs mounts.

Check this document for performance issues in NFS ( soft and hard mounts ):

http://us-support3.external.hp.com/cki/bin/doc.pl/sid=458df306029c556ebf/screen=ckiDisplayDocument?docId=200000013150468

HTH,
Shiju

[Wodisch]

Hello Sue,

are the *other* options for soft-mounts used?

Talking about:
- reply=
- retrans=
- timeo=

You could use these to increase the amount of time before the client aborts.

And not to *hang* you could use the "intr" option (interrupt key enabled).

HTH,
Wodisch