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Old 09-28-2011, 01:11 AM
Stephane Durieux
 
Default autofs interest ?

Hello,
A simple question:from a server point of view does autofs costs less (cpu, io, memory) than "traditionnal" nfs ?

From a client point of view I think the fact to unmount directories frees ressources?
But does a moint point consumes so much (memory ?)
And concerning the network

Thanks for explanation (or the little course)
 
Old 09-28-2011, 01:43 AM
Bob Proulx
 
Default autofs interest ?

Stephane Durieux wrote:
> A simple question:

> from a server point of view does autofs costs less (cpu, io, memory)
> than "traditionnal" nfs ?

AutoFS is simply a automated mount service for NFS. AutoFS doesn't
replace NFS. The autofs simply gets nfs going by mounting remote nfs
filesystems on demand. Therefore it will never cost more nor less not
using it with NFS. The server in particular does not run autofs and
so it does not matter there at all. Using AutoFS is very traditional.

However the automounter is often a source of problems of its own.
Often it will fail to mount a particular filesystem or it will unmount
one filesystem of a set and fail to mount it back again. When it
works it is wonderful. When it does not work it is a PITA.

> From a client point of view I think the fact to unmount directories
> frees ressources?

Yes. And most importantly reduces the total amount of time that the
nfs client is active. That reduces the opportunity for the nfs client
to get into a bad state and require that the client host be rebooted.
The nfs client getting into a bad state is the most likely reason to
require a reboot. Not having the nfs client running makes the system
more stable.

> But does a moint point consumes so much (memory ?)

I don't know the total amount but I never found it significant.

> And concerning the network

What about the network?

> Thanks for explanation (or the little course)

I use the automounter in a large corporate environment. There are
hundreds of machines potentially possible to be mounted. But at any
point only two or three are actually needed. Using the automounter
simplifies this large nfs configuration. But it comes at a cost of
complexity. The automounter sometimes causes its own problems.

There are three types of automount maps. Direct, Indirect, and Host.
Direct maps are the most reliable and the least trouble but most
configuration. Indirect maps are simpler and have various advantages
but also have some problems. Host maps are easiest and also have the
most problems. Asking about the autofs means you need to be thinking
about what type of automounter mapping configuration you will be using.

You should also want to look at the Berkeley Automouter 'amd' too for
an alternative implementation. The two designs each have their own
advantages and disadvantages.

Bob
 

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