Seth Vidal wrote:
>
> > I'd try an alpha machine, with 66MHz-64bit PCI bus, and interleaved
> > memory access, to improve memory bandwidth. It costs around $10000
> > with 512MB of RAM, see SWT (or STW) or Microway. This cost is
> > small compared to the disks.
> The alpha comes with other headaches I'd rather not involve myself with -
> in addition the costs of the disks is trivial - 7 75gig scsi's @$1k each
> is only $7k - and the machine housing the machines also needs to be one
> which will do some of the processing - and all of their code is X86 - so
> I'm hesistant to suggest alphas for this.
>
Look at the reality! If you have to do this sort of thing, x86 will give
you headaches. Normal 133MhZx32Bit PCI is _way_ too slow for that
machine. The entire PCI bus cannot saturate _one_ Ultra160 SCSI
controller, let alone a GigEth card. Putting More than one into a box
and trying to use them concurrently will show you what good normal PCI
is for _really_ fast hardware. You sure want multiple PCI64x66Mhz busses
and _now_ look again at board prices for x86.
Also, if you do data analysis like setiathome does (i.e. mostly FP),
alphas blow away _any_ other microprocessor (setiathome work-unit in
less than an hour; my AMD K6-2 500 needs 18hrs!) Code can be re-compiled
and probably should.
> > Another advantage of the alpha is that you have more PCI slots. I'd
> > put 3 disks on each card, and use about 4 of them per machine. This
> > should be enough to get you 500GB.
> More how - the current boards I'm working with have 6-7 pci slots - no
> ISA's at all.
>
Look, you are an the _very_ wrong track! You may have 6 or 7 PCI
_slots_, but you have only _one_ bus, i.e. only 133MB/sec bandwidth for
_all_ 6 or 7 devices. You will not get 90MB/sec real throughput with a
bus bandwidth of 133MB/sec! And the x86 architecture's memory bandwidth
is _tiny_ (BX chipset does one or two _dozen_ MB/sec random access, ie.
12-24 MB/sec).
> The alphas we have here have the same number of slots.
But not only one bus. They typically have 3 slots/bus.
>
> > Might I also suggest a good UPS system? :-) Ah, and a journaling FS...
>
> the ups is a must -the journaling filesystem is at issue too - In an
> ideal world there will be a Journaling File system that works correctly
> with sw raid :)
>
> -sv
--
Marc Mutz <[EMAIL PROTECTED]> http://marc.mutz.com/Encryption-HOWTO/
University of Bielefeld, Dep. of Mathematics / Dep. of Physics
PGP-keyID's: 0xd46ce9ab (RSA), 0x7ae55b9e (DSS/DH)
