Re: The cache problem of re-export NFS test

[Brian Chrisman <brchrisman@gmail.com>]

I don't think 'sync' will prevent data from going into cache, it just
means that a copy has to be on stable storage/disk as well.  Whether
there's a copy in memory wont matter.

On Thu, Apr 14, 2011 at 1:52 AM, Sylar Shen <kimulaaa@gmail.com> wrote:
> Hi Sage,
> Thanks for your reply. I really appreciated.
> I tried what you suggested to set the argument "sync" in /etc/exports.
> I also checked "man 5 exports" and it showed that sync means reply to
> requests only after the changes have been committed to stable storage.
> It didn't mention that the export server won't do the cache task.
> However, after I did the experiment, I found that the memory usage of
> Ceph-client still went up to maximum value while writing the data
> which means Ceph-client did the cache task.
> So...are there other possible ways to solve my problem?
> Thanks~~
>
> Best Regards,
> Sylar Shen
>
> 2011/4/12 Sage Weil <sage@newdream.net>:
>> On Tue, 12 Apr 2011, Sylar Shen wrote:
>>> Hi developers,
>>> I know that the following question may not be relative to Ceph but
>>> this confuses me a lot.
>>> I am testing the function of re-exporting nfs by command "dd" without
>>> using buffer.
>>> That means I would like my data to be written to Ceph DFS directly
>>> without passing by the buffer of client or nfs-client.
>>> Here is my test architecture. Hope you could understand what I am
>>> trying to express.....:p
>>> ------------------------------------------------------------------------------
>>>                 nfs                         ceph protocol
>>> Client <------------>Ceph-Client <-------------------> Ceph DFS
>>> ------------------------------------------------------------------------------
>>> I used the command "dd if=/dev/zero of=/mnt/ceph/test bs=64k
>>> count=10000 oflag=dsync"
>>> My purpose was to write the data from the client to Ceph DFS through
>>> Ceph-client.
>>> Ceph DFS was mounted by Ceph-client using Ceph protocol and
>>> Ceph-client was mounted by client using nfs protocol.
>>> I know that my dd command with argument oflag=dsync would write the
>>> data to Ceph-client without using buffer on the client.
>>> But I want my Ceph-client could also just pass the data to Ceph DFS
>>> without using its buffer.
>>> So.....is there any way I can run my scenario?
>>> Or in other words, is there any method I can assure that Ceph-client
>>> won't do the buffer task itself?
>>
>> I think what you're looking for is the 'sync' option in /etc/exports on
>> the ceph-client machine.  See 'man 5 exports'.  That will slow things down
>> considerably but will give you the consistency and safety you're looking
>> for.
>>
>> sage
>>
>
>
>
> --
> Best Regards,
> Sylar Shen
> --
> To unsubscribe from this list: send the line "unsubscribe ceph-devel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
--
To unsubscribe from this list: send the line "unsubscribe ceph-devel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html