[CentOS] Mounting NFS subdirectories individually or just the parent?

Frank Thommen lists.centos.de at drosera.ch
Thu Jul 28 08:41:22 UTC 2016


On the server side, the export is defined for /export/base, not for 
/export/base/x.  But I see the points.  It seems, that we should 
probably revisit our export/mount setup :-)

frank



On 07/28/2016 12:40 AM, Sean Brisbane wrote:
> There is a slight performance related reason for exporting disk partitions
> individually, the performance boost is server-side as Paul says.  The
> advantage is that the no_subtree_check can be used without any additional
> security risk.
>
> It is probably the case that the /export/base/a is a partition, is exported
> with no_subtree_check, and therefore there is a small performance boost.
>
> Preventing server side mount point traversal can also form part of a
> security mechanism if servers have different security options for different
> mount points, but in this case mounting server:/export/base wouldn't give
> you the same client view of the filesystem tree as mounting each
> individually if it worked at all.
>
> Cheers,
> Sean
>
> On 27 July 2016 at 23:21, Paul Heinlein <heinlein at madboa.com> wrote:
>
>> On Wed, 27 Jul 2016, Frank Thommen wrote:
>>
>> Hello,
>>>
>>> does it in any respect (throughput/performance, cpu load, I/O load,
>>> resilience, ...) matter, if one mounts subdirectories of an NFS (v3) export
>>> into separate directories or if one just mounts the parent directory?
>>>
>>> I.e. like this:
>>>
>>>  server: /export/base/a -> /mnt/a
>>>  server: /export/base/b -> /mnt/b
>>>  server: /export/base/c -> /mnt/c
>>>  server: /export/base/d -> /mnt/d
>>>  server: /export/base/e -> /mnt/e
>>>
>>> or simply like this:
>>>
>>>  server:/export/base   -> /mnt
>>>
>>
>> Performance wise, any bottleneck will almost certainly be tied to the
>> disks on the back end, not the nfs process itself.
>>
>> There are a couple good reasons for splitting up the mounts:
>>
>> 1. They can have different export restrictions (e.g., for different
>>    client hosts, ro vs. rw permissions, user squashing).
>>
>> 2. /base/[a-e] live on different RAID arrays and might benefit from
>>    different management cycles; that'd also be a case where multiple
>>    exports might be a good idea. That said, I've never managed an
>>    exported filesystem consisting of different arrays; we've always
>>    exported at the RAID level or below.
>>
>> --
>> Paul Heinlein <> heinlein at madboa.com <> http://www.madboa.com/
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