CCL:Largest Linux Cluster?

[Ron Brightwell]

>
> > Sandia National Laboratories has C-Plant that runs Linux in addition to several
> > layers of home-grown OS on several thousand nodes. The basic node is a DEC 
> > ev6 with myranet (sp). They use no local disk, opting for a huge disk farm.
> 
> do you happen to know how they manage the huge disk farm???
> 	- resumably raid5 systems...
> 	- are each raid5 sub-system dual-hosted so that the other cpu
> 	can getto the data if one of the cpu cant get to it
> 	- does all nodes access the "disk farm" thru the gigabit ethernet
> 	or dual-hosted scsi cables ??
> 	- how does one optimize a disk farm ?? (hdparm seems too clumbsy)
> 
> -- in the old days.... 1980's ... there used to be dual-hosted
> disk controllers where PC-HOST#1 and PC-HOST#2 can both access the same
> physical CDC/DEC/Fujitsu drives
> 	- wish i could find these dual host scsi controllers for todaysPCs
> 

The Cplant clusters use a parallel I/O system called ENFS, which is a modified
version of the NFS protocol that avoids locking and doesn't provide full
UNIX semantics.  Compute nodes send parallel I/O requests via ENFS to a set
of proxy I/O nodes that mount a back-end filesystem through gigE uplinks.
In the case of the 1792-node cluster, the back-end is an SGI O2K running XFS
(I think).

-Ron