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 <heinl...@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 <> heinl...@madboa.com <> http://www.madboa.com/
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