ADSM-L

Re: Win 2K VS AIX

2002-05-13 09:31:47
Subject: Re: Win 2K VS AIX
From: Zlatko Krastev <acit AT ATTGLOBAL DOT NET>
Date: Mon, 13 May 2002 16:29:31 +0300
Michael,

That's why I wrote "I am aware of". I have not very close look at PC
servers market - it is moving very fast. So I am asking detailed
specifications on demand.
Will have a look at this ones you point to. I was not precise - in the
past they were secondary, now are primary but small. If we count "full"
buses - you can put FC (200-240 GB + duplex) or RAID adapter (usually
3-4xUltra160) only on 64-bit/66MHz. You still can have GB Ethernet on
64-bit/33MHz "half" bus (alone !). And for more than 20-50 nodes (depend
on size) you will need several LAN adapters if GB and tens of Fast Ether.
For ServerWorks chipset - it may support up to four buses but how many are

routed on the planar and at what speed. For example we now are installing
TSM for a customer on IBM x342 (it is based on this chipset). The server
is having 3 primary buses but only one is 64-bit/66 MHz and two slots on
it (others are 64/33MHz and 32/33). So IBM itself states you can have
ServeRAID or FC adapter in it but NOT both.
Three buses with 1.1GB/s (it ought to be 1066 MB/s) means two primary and
one secondary, i.e. one 2 Gb/s FC HBA + 2x 1Gb Ethernet or 2x 2GB/s FC.
More with congestion and performance degradation. But what if bus 1 is
64-bit/66MHz (533) and 2,3 are 64/33 (2x 266). You already lost the option

2x FC. Having into account SCSI for boot/paging + (1 or 2) 100 Mb Ethernet

....
OTOH 4x 64-bit/66MHz = 4x 533 MB/s = 2133 MB/s. If for marketing reasons
rounded up and later multiplied it would give you 4x 533 MB/s = 4x 0.6
GB/s = (those fictious) 2.4 GB/s. I've studied mathematics and we are
calling this propagation of the error.
On the example above you can see what IBM shows (I would not say
cheating). Others do the same. So again ask hard questions:
how many buses
how many bridges
width and speed of *each* slot
which slot to which bus (IBM x342 case - bus A 32/33, slot 1; bus B
64/66, slots 2&3; bus C 64/33, slots 4&5)
Better ask them to draw a picture what goes where and how is connected
(you will become their nightmare :-)
Those 2-way boxes have no enough real estate on the planar for full
routing of all buses. Thus one bus is routed with many & short wires -
64-bit/66Mhz. Second is routed with many but long wires - 64-bit/33MHz.
Last used what left from others - only 32-bit/33MHz. For the fourth port
of the chipset there is no place to route the wires to a slot - cut off.
So first bus is good for FC/GB Ether/RAID, second for SCSI/small RAID/some

Fast Ether, third for Fast Ether + boot SCSI + ISA (management, serial,
kbd, mouse,etc.)
BTW: I checked again x440 and proved myself wrong in part - still four
buses per drawer but only 2 drawers, i.e. max I/O 4GB/s.
My intention is not to scare you or irritate but to show you the hidden
part of the truth. That's why I will submit this to the list on copy.
And on the end you are missing an important point measuring the bus
throughput. Data does not go "Ether ---> disk" or "ether --> tape".
Transfer is "LAN --> memory buffer --> FC/SCSI". And if you setup diskpool

for staging data goes "LAN --> memory --> FC/SCSI (disk) + FC/SCSI (disk)
--> memory --> FC/SCSI (tape)", i.e. four transfers. So calculate all the
simultaneous clients (not all can send direct to tape unless you have very
simultaneous clients (not all can send direct to tape unless you have very

huge silo).
Sorry, this again became too long explanation. I still think with the
figures you have shown current H70 should not need too much upgrade (if
any). Do you have any slots free there?

Zlatko Krastev
IT Consultant




Please respond to bruewer AT uni-hohenheim DOT de
To:     Zlatko Krastev <acit AT ATTGLOBAL DOT NET>
cc:

Subject:        Re: Win 2K VS AIX

On 12 May 2002 at 16:22, Zlatko Krastev wrote:

> All 2-proc SMP Intel boxes (I am aware of) are having one primary PCI
bus
> and secondary through PCI-PCI bridge. Thus all the I/O performance such
a
> box can have is 533 MB/s total (DB disks, stgpool disks, tapes, LAN).

Hello,

I don't want to recommend running TSM on W2K. But I am looking for
such servers for other purposes and your statement irritates me. For
example Intel's dual PIII board SDS2 is described as follows:

"Triple Peer PCI buses: Separate PCI buses to help eliminate data
bottlenecks, increase bandwidth for intensive I/O needs, and provide
up to 1.1 GB/sec of data transfer."
Many 2-proc SMP Intel boxes are based on the ServerWorks HESL chipset
which even supports four independent buses with a bandwith of 2,4
GB/s.

A board with four 64/66 PCIslots and 1,1 GB/s bandwidth could handle
e.g. 2 x U160 SCSI RAID (onboard) + 2 x 2Gb FC + 2 x 1Gb Ethernet,
which seems quite a lot to me - at least for a medium sized
environment like ours.

I can't find numbers in the descriptions of those 10K$ dual PIII SMP
boxes of IBM, Dell or FSC, but all are talking about "Triple PCI
Architecture or "Two independent PCI-buses". Are they trying to fool
me?

Kind regards,

Michael Bruewer
----
Dr. Michael Br"uwer
Dr. Michael Br"uwer
RZ der Univ. Hohenheim     70593 Stuttgart
bruewer AT uni-hohenheim DOT de   www.uni-hohenheim.de/~bruewer
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