[geeks] SGI-HOWTO

[Big Endian]

>That's a 256node cluster (256 dual proc system boards with up to 8 (iirc
>might be 4) gig of ram each) totaling several terabytes of ram.  The only
>limitation on storage is the ammount you care to attach, at several XIO
>slots per system chassis (4 systemboards/chassis) and 4uw scsi or 2 FC-AL
>ports per XIO slot I'm sure you can imagine the ammount of storage you
>could attach.  You end up with 64 ethernets alone.  The only limits on
>this hardware are software, and being irix has been 64 bit for
>years.....  I'm sure there is a limit on the total diskspace you can use
>in irix, but if anyone knows it I'd really like to know.
>	Nick
Its not really a cluster but a NUMA(Non-Uniform Memory Access) based 
machine.  Each system board has full access to the other system 
boards' ram and there is cache coherency among *ALL* cpus(at least on 
SGI systems, not all NUMA machines are cache coherent).  Its a sick 
and twisted system but it gets *REALLY* hard to build something like 
a 512cpu machine without it.

Each board can handle 4cpus (r12k 400s) and 8gigs of ram(think an 
octane or origin200, but in a modular board and 2 more cpus). 
http://www.sgi.com/origin/3000/bricks.html gives an example of what 
these things have in them.  The origin 3k series has only one basic 
I/O module per system (fiberchannel disk, cdrom, PCI slots, ethernet, 
USB and FireWire).   I'd say SGI sells perhaps 1-2 of the high end 
units a quarter, if that.
XFS(sgi filesystem) scales to hundreds of terabytes, perhaps multiple 
petabytes and its journaling and faster than UFS.  There is a reason 
to buy sgi systems.  IRIX was designed from the begining of the Power 
series to be SMP friendly and Its had 64bit support since the R4k and 
Irix 6.  Their technology is to say the least impressive. 
Unfortunately their prices more than make up for it when buying new.

daniel