[CentOS] Fwd: Bug 800181: NFSv4 on RHEL 6.3 over six times slower than 5.8

Tue Jul 17 09:33:21 UTC 2012
Johnny Hughes <johnny at centos.org>

On 07/13/2012 07:40 AM, Les Mikesell wrote:
> On Fri, Jul 13, 2012 at 7:12 AM, mark <m.roth at 5-cent.us> wrote:
>> *After* I test further, I think it's up to my manager and our users to
>> decide if it's worth it to go with less secure - this is a real issue,
>> since some of their jobs run days, and one or two weeks, on an HBS* or a
>> good sized cluster. (We're speaking of serious scientific computing here.)
> I always wondered why the default for nfs was ever sync in the first
> place.  Why shouldn't it be the same as local use of the filesystem?
> The few things that care should be doing fsync's at the right places
> anyway.

Well, the reason would be that LOCAL operations happen at speeds that
are massively smaller (by factors of hundreds or thousands of times)
than do operations that take place via NFS on a normal network.  If you
are doing something with your network connection to make it very low
latency where the speeds rival local operations, then it would likely be
fine to use the exact same settings as local operations.  If you are not
doing low latency operations, then you are increasing the risk of the
system thinking something has happened while the operation is still
queued and things like a loss of power will have different items on disk
than the system knows about, etc.  But people get to override the
default settings and increase risk to benefit performance in they choose to.

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