novice question about large write requests

novice question about large write requests

[Venkatesh KS]

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Folks,

I am trying to understand how nfs client handles a server reboot while
issuing multiple
unstable writes followed by a commit.

Say a user requests a large write requests.
nfs client breaks it into multiple 32k requests, each 32k write request
being unstable
and finally a commit call before the nfs client returns back to the user.

If the server reboots in between these write calls, will the nfs client know
abt it.
The write before this may not have made it to disk. If the nfs client doenst
know
abt it then it goes ahead with commit call and returns.

regards,
-venkatesh

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Re: novice question about large write requests

[Peter Staubach]

Venkatesh KS wrote:
> Folks,
>
> I am trying to understand how nfs client handles a server reboot while 
> issuing multiple
> unstable writes followed by a commit.
>
> Say a user requests a large write requests.
> nfs client breaks it into multiple 32k requests, each 32k write 
> request being unstable
> and finally a commit call before the nfs client returns back to the user.
>
> If the server reboots in between these write calls, will the nfs 
> client know abt it.
> The write before this may not have made it to disk. If the nfs client 
> doenst know
> abt it then it goes ahead with commit call and returns.

I would suggest checking out RFC1813 for information on this topic.

       ps

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Re: novice question about large write requests

[Chuck Lever]

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Peter Staubach wrote:
> Venkatesh KS wrote:
>> Folks,
>>
>> I am trying to understand how nfs client handles a server reboot while 
>> issuing multiple
>> unstable writes followed by a commit.
>>
>> Say a user requests a large write requests.
>> nfs client breaks it into multiple 32k requests, each 32k write 
>> request being unstable
>> and finally a commit call before the nfs client returns back to the user.
>>
>> If the server reboots in between these write calls, will the nfs 
>> client know abt it.
>> The write before this may not have made it to disk. If the nfs client 
>> doenst know
>> abt it then it goes ahead with commit call and returns.
> 
> I would suggest checking out RFC1813 for information on this topic.

There is also some explanation of this in the Linux NFS FAQ:

   http://nfs.sourceforge.net/

and we've found Brent Callaghan's "NFS Illustrated" to have some useful 
explanation of reboot recovery with unstable writes.

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