number of nfsd processes

[Thomas Narten]

>In blue sky theory, the number of nfsd processes should be equal to the
>number of discs you have plus two; this to cover the possibility where all
>the discs are busy, one nfsd is working the ethernet (if you have more
>than one ethernet interface more than one nfsd could be reading or writing
>to the ethernet) and one nfsd is running the CPU as well.

If the disk device drivers are written in any sort of reasonable fashion,
there is no reason not to have many more simultaneous disk operations than
disk drives.  The driver should reorder queued operations to minimize seek
times.  Thus, increasing the number of nfsds might actually increase
througput.  Without looking at the code, I dunno of Sun drivers do that.
I also understand that SCSI disks really muck this up too, because the
driver really doesn't know how the disk is layed out.  This is bad news of
course, because it means that the Berkeley Fast File System layout
policies aren't used on such disks.

>If you have fewer nfsd processes, specially under SunOS 4, the number of
>context switches will go down dramatically, especially if your server is
>used mostly for NFS service.

But this isn't really helpful.  If an nfsd has to wait for a disk
operation, a context switch will take place anyway.  Better to have a
active process to switch to than just sit idle.

Thomas Narten