On Wed, Feb 06, 2008 at 07:12:55AM -0500, Nick Holland wrote:
> Douglas A. Tutty wrote:
> > I'm wondering how scsi external arrays work in OpenBSD. This is in
> > relation to my low-MHz box search. Sata drives have too fast a clock
> > rate so it will be scsi.
>
> Are you speculating, or have you actually tested the results here?
> A new 300G SATA vs. an old 2G SCSI? You are probably right. Compared
> to a 36G or 140G SCSI? I'd not be so sure.
So far, just comparing wikipedia articles: sata bitrate, since its
serial, is roughly the same as its b/s rate. Scsi clock rate,
presumably, is as reported by wikipedia.
[snip]
> Sun made both types of systems. Make sure you know how to configure
> the boxes with their own local controller. The "box of disks" ones are
> pretty easy to configure. :)
Before my eBay search and subsequent reading of box manuals, I thought
that they were all 'box of disks' and don't need anything more than
this. However, right now, on eBay they're all ones with a local
controller. Presumably, boxes of disks are cheaper than boxes with a
controller.
> Not sure how much storage you are after here, but I'm not sure I believe
> that ten 9G disks are "better" for your quest than one 100G disk.
I'm not thinking of starting off with 12 disks. I'm looking at the
concept of a server with many bays (which I what I was imagining) vs a
server with 1 or 2 bays and an external box for more bays. Presuably as
things switch from parallel scsi to SAS, parallel scsi boxes will become
scarce in the free/used market.
Slow computers aren't going to be made anymore. Whatever I get, will
have to last (even if I end up getting a bunch to use as parts in the
future). I need to start with about 18 GB of drive space. When I need
to add more, I don't know what will be available so I want to have the
bays up-front.
> ONE 9G vs. ONE 100G? Maybe (and even then...keep in mind that SATA
> cables are shielded, PATA and older SCSI cables are not really
> shielded), but the fact that you need a lot of them and they use more
> cabling is very possibly going to "add up" on you.
True. Ideally, I'll keep the number of drives small. Weather a box of
disks means a lot more cabling is debatable if the boxes are
side-by-side and the box has a back-plane.
The SATA cable may be shielded, but it runs at 1.5 or 3 Gb/s.
Therefore, the controller will have circuity unshielded except by the
box which also runs that fast.
Unshielded SCSI cable?
> Also keep in mind that when you go past about 9G on SCSI drives, many
> are 160MB/s transfer speeds; even if you attach them to an old
> controller, the processor on the drive is capable of handling that
> speed, and didn't slow itself down.
>
160 MB/s spread over a parallel interface should still be a frequency
less than 200 MHz.
> Again, years ago, home-grade stuff used to emit less RF than "business"
> grade stuff. Sun and HP disk chassis never were intended to be in a
> home. IF you are trying to minimize RF, disk chassis probably aren't
> want you want. If you are trying to minimize EMF, the higher power
> consumption of the disk chassis is probably not what you want. And I
> doubt the extra cables between the chassis and the computer are going
> to be your friends.
This may all be true. The trouble is, old home-grade stuff is long gone
and wasn't designed to last. Years ago, you'd be comparing a 386
home-grade with a SPARC, PA-RISC, or perhaps PPC server. Now,
everything runs the same stuff: Opteron/Athlon64, Xeon, Core2Duo, etc.
and the home grade stuff is in plastic boxes.
It sounds like, if I am going to use a server, I'd be better with one
with more bays and forget the external box.
What about a Compaq Proliant 2500R on eBay for $300?
max 1 GB ram, 1 PCI bus over 6 slots, dual Pentium Pro 166 MHz
4 bays + 2 1/2 height bays (for media) + CDROM and floppy
Thanks for your thoughts.
Doug.
