Stewart Stremler wrote:
256, if I remember right.
Ah, LOTS of room. :)
Indeed. Lots of room for lots of devices. Keep in mind that you can have
fibre tape drives, media changers, and other such devices as well.
NetApp et al reccommend you don't connect more than 28 disks (two
shelves) to a 1Gbps FC loop, 48 to a 2Gbps loop, and 96 to a 4Gbps loop.
Which makes sense, as you can easily saturate the bus with that many
devices.
It's less stressful to add suddenly-needed storage by simply adding
more disks than it is to add more disks *and* additional controllers,
even if in the long run adding the controller is needed for performance.
Oh, undoubtedly. In 99% of cases, adding the additional adapter will
require an outage, whereas adding a single disk (or even a shelf) can be
done hot(1) and is completely transparent to the user.
Even if it's not the best thing for performance reasons, it may be the
best idea if you can't afford to take an outage. If that's the case
though, one would suggest better growth planning (like having a hot
adapter ready for additional disks in the event they are necessary).
(1) Shelves can't easily be added to copper loops, as in order to add a
shelf you have to open the loop by removing the terminator. Optical
loops are switched(a) and therefore don't suffer from this problem.
(a) Not all manufacturers switch their optical loops -- as always, check
your manuals.
> Drive-juggling with IDE is a PITA.
Drive juggling, period, is a PITA. Device ID by WWN is the only way to
go. Fibre Channel started this, and SAS picked up on the idea (and oh,
what a great idea it was). SAS adapters also have the added benefit of
supporting SATA disks (albeit at a lower speed).
Cheers,
-Kelsey
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