Bus architecture was RE: [SunRescue] Re: NetApps?

[Chris Byrne]

At the risk of a "mee too" here, I agree with you entirely. If you have a
lot of cache (on the cards, in the disk, and in the system itself) then you
can do some pretty amazing things with big bursts.

That's one of the reasons I love my IBM U160 UltraStar drives. 4MB of cache
per drive, and enough media transfer rate to use it all. I have six of them
in my JBOD box (6 drives, raid 5, 2 groups, 2 and 1 each group, single
logical volume with veritas volume manager. The joys of working for a
storage company) and man do they scream. Of course it's running in a windows
environment since my raid controller is an adaptec 'nee DPT windows only
card, so it's not seeing it's full potential, but it's still very nice.

Hitachi is bringing out a 72gb 10k rpm FC-AL drive with 16mb of cache per
drive for their really high end storage customers. They were starting to
roll out a model with a little less cache when I left my previous employer,
but they had failures all over the place.

As far as I know it will only be sold for Hitachi Freedom 9000 large scale
storage arrays (a cool 2 million a pop just for starters). Those bad boys
are some serious storage. Each array can have up to 32gb of cache, and 512
disks for a raw capacity of around 37TB. The last company I worked for had
20 of them and was buying more. They eventually planned to have 150.

We did a power study on them, and each box by itself uses the same amount of
power as a small office building if you count the air conditioning required
to cool them (90+ kva and 90+ kw heat when fully loaded). They weigh 4 tons,
and are up to 20 feet long.

They actually had to remove the wall of one of the buildings we installed
in.

Wouldnt you love one of those for your house ;-)


Chris Byrne


-----Original Message-----
From: rescue-admin at sunhelp.org [mailto:rescue-admin at sunhelp.org]On
Behalf Of Bjorn Ramqvist
Sent: Tuesday, March 20, 2001 23:23
To: rescue at sunhelp.org
Subject: Re: Bus architecture was RE: [SunRescue] Re: NetApps?



> Note, this is a major reason why an u160 device in your PC isn't generally
> any faster than an FC-AL device (probably not much faster than your 80MB/s
> stuff), and one of the reasons why full duplex gig-e is pointless to the
> desktop.

No, but the U160 standard unlocks another rather impopular phenomena, a
choked bus.
Many of us already know that you can hook up to 15 devices on a standard
16-bit (Wide) SCSI-bus. However, even if you have all this Ultra2 fancy
stuff (80 MB/s), you could choke the bus if you read/write aggresivly
with large sequential files. (typical fileserving)
So, practicly you can only hang upto 3,4 or maybe 5 quick devices on a
heavily used SCSI-bus. If we don't wanna go for dual- or maybe
triple-channel, we go for even higher speeds (even though the drives
won't ever come close to the speed). This enables higher "burts" (direct
cached reads) and more devices on the same bus, without choking it.
Compaq (and others) are already looking at the next proposed standard,
SCSI-3, or "Ultra320".

This scenario isn't really on the desktop either, where we have (as
you've said) already bottlenecks in the architecture. But for big fat FC
RAID-controllers (external), this could cut the pricetag down when
volume goes up, and still make a tremendous bandwidth out of just one
channel. Right now it's popular spreading bandwidth among several
SCSI-buses, 2, 3, or even 6 buses, just to keep the FC busy and still
manage to get away with SCSI-devices.

> Now if the infiniband stuff ever gets off the ground, or if manufacturers
> would finally switch to 64 bit 66Mhz bus architecture, then maybe we would
> be able to effectivley use high bandwidth devices like GigE, and the
higher
> end SCSI. Now prototyes are in the works for 2Gb/s ethernet, and 400MB/s
FC
> devices. Nothing we have available on the desktop and low-midrange server
> market today could effectivley use these things.

It's a good thing we are almost stucked to 64-bit/66MHz devices here at
work, both on SGI and the Alphas. It's just those PeeCee-servers that,
for some reason, sometimes comes with 32-bit cards, even the Fibre
Channel adapters.
PCI-64 in all it's glory, but infiniband seems to be somewhat
interesting.

/Bjorn
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