Sun disk space expansion/migration options/opinions wanted

[Skip Montanaro]

Our group of 10-15 people currently gets most of its /home disk space from
two Encore Multimaxes maintained by a central support group. In order to
get us off their machines, they are willing to buy us some storage for our
group's file server.

Their current proposal is to add a Xylogics 7053 and two 2.5 GB disks
(Hitachi?) from NPI to our 3/260. Our client computers consist of nine
4/6[05]GX workstations, each with 16MB of physical memory and 104MB local
disks containing root and swap. We have a few other odds'n'ends, such as a
diskless 3/60, a couple diskless 3/260s, and a 386i (with disks).

My feeling is that, without some reinforcements, the 3/260 file server
will be overburdened with the increased disk load, even though most (and
eventually all) clients will have local root and swap partitions.

My alternatives appear to be:

1. Go with the proposal as it stands and see what happens, making
   adjustments as we go,

2. Purchase an extra 7053 and turn one of the other 3/260's into a second
   file server,

3. Purchase an I/O subsystem accelerator of some sort, such as OMNI
   Solutions' or Legato's products, 

4. Upgrade to a full-fledged file server, such as an Auspex NS5000, or 

5. Scatter large external SCSI disks (like HP's 660MB or 1GB disks) around
   the 4/6x's in our offices, effectively making each share some of the disk
   load.

If I knew for certain that something like an Auspex was in the cards, I'd
opt for SCSI disks compatible with it (HP 660MB now, 1GB later), and move
them when the file server arrived (a combination of #5 this year, followed
by #4 next year).  Due to its expense, however, an Auspex would likely be
shared with a larger organization, with attendant complications in
evaluating, ordering, and maintaining it.

I am in the process of estimating our group's NFS request pattern on the
Multimaxes using Encore's server_stat program. If the write request
percentage is not high enough, then an NFS write accelerator like Legato's
Prestserve probably won't help much, although OMNI's product would
probably still help.

I'm pretty confident that Sun-3s can serve Sun-4s, in principal, if you
can drive the CPU load down by either replicating CPUs or offloading the
CPU with special-purpose I/O subsystems. (After all, the Auspex NS5000 has
a Sun-3 VMEbus-based CPU.)

I would appreciate feedback from people with any suggestions. The Sun-3 to
4/6x route seems pretty common these days, so there must be some useful
experience out there. Here are some questions we can't currently answer
and/or won't be able to investigate thoroughly in the time we have
available:

1. How bad would the added noise and heat be with large external SCSI
   disks hung off 4/6x's?

2. Would something like the OMNI or Legato accelerators allow us to use
   SCSI disks instead of the more expensive (and less flexible) SMD disks?

3. Sun doesn't currently maintain the proposed configuration. What
   alternatives are there for short turnaround (< 24hr) maintenance?

4. What other architectures are we neglecting? SPARCserver-1s with several
   large SCSI disks come to mind. What kind of experience have people had
   with them?

I will summarize the responses to sun-managers and sun-spots.

Thanks,

Skip (montanaro at crdgw1.ge.com)