[Beowulf] diskless booting over jumbo frames
Bogdan.Costescu at iwr.uni-heidelberg.de
Wed Apr 25 08:45:41 EDT 2007
On Tue, 24 Apr 2007, Mark Hahn wrote:
> so the main question is whether jumbo is worth the effort.
I would rephrase it to say: whether jumbo is worth the effort for the
root FS. When I used NFSroot, most of the traffic was queries of
file/dir existence and file/dir attributes, which are small, so a
large maximum packet size would not help. Furthermore, most of the
files accessed were small which means that the client could be quite
successful in caching them for long times and the actual transfer (if
the cache is emptied) would not take too long.
I think that it is more important to think thoroughly the placement
and exporting of the files on the NFS server. If you can manage to
export a single directory which is mounted as-is by the clients and
have the few client-specific files either mounted one by one or
copied/generated on the fly and placed on a tmpfs (and linked from
there), you can speed up the serving of the files, as the most
accessed files will stay in the cache of the server. The Stateless
Linux project from Red Hat/Fedora used such a system (single root FS
then client-specific files mounted one by one) last time I looked at
> here's a cute hack: if you're using pxelinux, it has an "ipappend" feature,
> I haven't had time to try this...
It works as you described it.
But even the first idea that you mentioned, using dhclient to get an
IP would work just as fine if the number of nodes is not too big - I
have 100+ nodes configured that way, with 2 DHCP requests per boot of
node (the PXE one and the dhclient one) as I was just too lazy to try
to eliminate the second DHCP request by re-using the info from PXE -
and the master node doesn't feel the load at all, although it is
hardware-wise the poorest machine from the cluster (as opposed to most
other clusters that I know of ;-)).
IWR - Interdisziplinaeres Zentrum fuer Wissenschaftliches Rechnen
Universitaet Heidelberg, INF 368, D-69120 Heidelberg, GERMANY
Telephone: +49 6221 54 8869, Telefax: +49 6221 54 8868
E-mail: Bogdan.Costescu at IWR.Uni-Heidelberg.De
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