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RP8400 SPOFs

 
Asghar Ghori
Occasional Advisor

RP8400 SPOFs

Does anyone know what the single points of failure are in the RP8400 servers.

I also need to have a diagram that shows the entire box hardware architecture.

Thanks
14 REPLIES 14
Joshua Scott
Honored Contributor

Re: RP8400 SPOFs

as for the architecture, see here:

http://docs.hp.com/hpux/hw/index.html#rp8400%20Server

The 'HP System Partitions Guide: Administration for nPartitions' has a diagrams on page 39, (on the PDF file) and may have some more throughout.

as far as SPOF, the Backplane is tha only thing I know of. The HA feature include:

N+1 hotswap cooling

Redundant and HotSwap power supplies

Cell Hot Plug

hot-plug disks

2N power inputs

Online memory page deallocation

ECC protected SyncDRAM memory

Full parity protection of data and address buses

On-Chip CPU cache w/ ECC protection

Memory "Chip spare", "Chip kill" like

CPU deallocation on failure

On-line addition and replacement of PCI I/O cards

Four Independant UltraSCSI buses to internal disks for mirroring across disks and controllers

Journal File System

Auto Reboot

On-line Diagnostics and system health Monitor

HTH.

-Josh
What are the chances...
Jeff Schussele
Honored Contributor

Re: RP8400 SPOFs

Hi,

Backplane, I believe, in this case means the interconnect between the two cell boards.
I think another is the PCI interconnect between the 2 PCI busses (sp?).

Rgds,
Jeff
PERSEVERANCE -- Remember, whatever does not kill you only makes you stronger!
Joshua Scott
Honored Contributor

Re: RP8400 SPOFs

I beleive you're correct, jeff.
What are the chances...
Stefan Stechemesser
Honored Contributor

Re: RP8400 SPOFs

The two halfs of the PCI Backplane are completely independent from each other (except they are on the same board and cannot be changed independendly). Each half has 8 seperate PCI busses connected to a system bus adapter which is connected to a cell controller on the cellboard. If one cell want to access IO connected to another cell, it has to connect via the cell to cell connections on the backplane. There is no direct PCI to PCI bridge or soomthing like this. If one half of the PCI cardcage fails completely (power is also independent) the partition has still the I/O of the other half (if configured redundant).

=> PCI is no SPOF

(OK, I forgot to say that the system crashes if on half of the PCI backplane fails, because HPUX does not like something like this, but after the reboot you can continue working without the 2nd half of your PCI cards ;-)
Michael Steele_2
Honored Contributor

Re: RP8400 SPOFs

Perhaps you should be looking at single points of failure in a nPar environment on a RP8400 as well. For I believe a single point of failure exists with boot disk controllers in a npar environment. Because boot disks can't be shared amongst npars. You run out of internal disk controllers quickly for this reason. For example, 2 partitions with one internal disk controller on either npar. Because boot disks can't be shared between npars this means the primary and alternate boot disks are on one controller. And unless you buy 2 additional disk controllers for a 2 npar configuration your internal boot disk controller becomes a single point of failure.

Now build a 4 npar environment. Eight boot disk controllers and 16 disks to cover all the primary and alterate boot disks for 4 npars.

So boot disks as well are SPOF's in a npar environment.
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Michael Steele_2
Honored Contributor

Re: RP8400 SPOFs

Sorry, "...16 disks..." should be "...eight..."
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Joshua Scott
Honored Contributor

Re: RP8400 SPOFs

Michael,
The rp8400 comes standard with 4 controllers, and only goes to 2 nPars. Thus you have redundancy on the controllers, if you have all 4 internal drives, and add mirrordisk (which I am assuming would be done if one is concerned at all about High Availability)

The only way the tp8400 goes to 4 npars is if the Server Expantion Unit(SEU) is added. the SEU is another enclosure with 4 more internal disks and 2 more Removable Media bays, as well as 16 more I/O slots and 2 more core I/O cards. Thus, even when going to 4 nPars, you still get redundant disks/disk controllers.

-Josh
What are the chances...
Michael Steele_2
Honored Contributor

Re: RP8400 SPOFs

Gee, I guess.

This SPOF with disk controllers and boot disks has been around, is a known problem and is especially a problem in HA SG environments.

As you stated there are four SCSI controllers but the RP8400 can support 4 partitions. That's one controller per partition.

See page 86:

http://docs.hp.com/hpux/onlinedocs/hw/rp8400/en/documentation/cust.pdf

#############################################
############################################

Here a chart of the 4 standard nPar config. for an 8400, note 4 is standard except in HA environments:

http://docs.hp.com/cgi-bin/fsearch/framedisplay?top=/hpux/onlinedocs/5187-3603/5187-3603_top.html&con=/hpux/onlinedocs/5187-3603/00/00/28-con.html&toc=/hpux/onlinedocs/5187-3603/00/00/28-toc.html&searchterms=rp8400&queryid=20031009-084852

#############################################
############################################

Here is an 'ioscan' from an nPar server, not necessarily an 8400. Please note that all the internal boot disks are on same controller at SCSI targets 5 and 6, while the controller is on target 7. Also note that this is for SCSI bus priorities.
Target 7 has high priority and is always reserved for the SCSI controller. While targets 6 and 5, then next lowest priorities, are always reserved for boot disks.

12/0/6 ba Local PCI Bus Adapter (782)
12/0/6/0/0 ext_bus SCSI C87x Ultra Wide Differential
12/0/6/0/0.5 target
12/0/6/0/0.5.0 disk SEAGATE ST39173WC
12/0/6/0/0.6 target
12/0/6/0/0.6.0 disk SEAGATE ST39173WC
12/0/6/0/0.7 target
12/0/6/0/0.7.0 ctl Initiator

http://docs.hp.com/cgi-bin/fsearch/framedisplay?top=/hpux/onlinedocs/5187-3603/5187-3603_top.html&con=/hpux/onlinedocs/5187-3603/00/00/17-con.html&toc=/hpux/onlinedocs/5187-3603/00/00/17-toc.html&searchterms=controller&queryid=20031009-085141

#############################################
############################################

Other issues with SPOFs"

For high availability environments where SPOF's are critical, please note this quote from the URL below:

"...The PRI and HAA paths should be configured to reference disks that are connected to different cells,..."

#############################################
############################################
nPartitions Guide:

http://docs.hp.com/hpux/onlinedocs/hw/rp8400/en/documentation/spg.pdf

#############################################
############################################

As others have pointed out, SPOF at the 2 core I/O boards through power which flows through single PCI back plane.
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Joshua Scott
Honored Contributor

Re: RP8400 SPOFs

Michael,

I will have to disagree with you. The rp8400 does not support 4 nPartitions. See here:

http://docs.hp.com/cgi-bin/fsearch/framedisplay?top=/hpux/onlinedocs/5187-3603/5187-3603_top.html&con=/hpux/onlinedocs/5187-3603/00/00/28-con.html&toc=/hpux/onlinedocs/5187-3603/00/00/28-toc.html&searchterms=rp8400&queryid=20031009-084852

Note at the bottom of this document it states:
"On rp8400 servers, each nPartition must include either cell 0 or cell 1 because these two cells are the servers' only core-capable cells"
A 'core-capable' cell is necessary for an nPartition, therefore with only 2 core-capable cells you cannot have more than 2 nPartitions.

-Josh
What are the chances...
Michael Steele_2
Honored Contributor

Re: RP8400 SPOFs

Thank you for pointing that out to me. I believe that you're right.

:-)
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James Anker
Valued Contributor

Re: RP8400 SPOFs

Mike & Josh are both right or at least they will be. Any day now HP will release a second twin I/O card cage/Core I/O board that will allow the RP8400 to support 4 x Hard Partitions using its 4 x Cell boards. Other change include the next generation of PA RISC that will have 2 x CPU cores on one physical CPU (like Power 4 from IBM) the RX version of the RP8400 will be released called the RP8620 - this will also have dual CPU's in the very near future based on IA64 but this version will rely on a daughter board and hence be S/W licensed as 2 x CPU's not one as in the PA RISC version. The same will happen in the RP7410 - This will be called the RP7620 under Itanium and again will double up on the number of CPU's.

Therefore:

RP7410 will be 16 x way capable
RP8400 will be 32 x way capable

There are other changes in the RP5400 space two if anyone interested...?

Cheers

James


Cheers

James
Michael Steele_2
Honored Contributor

Re: RP8400 SPOFs

There's a reason why I'm called...

....the man of steel.
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Joshua Scott
Honored Contributor

Re: RP8400 SPOFs

In the interest of being fair, HP had promised 4 partitions for the rp8400 long ago, and the SEU, as James pointed out will increase the capabilities of the rp8400/rx8620 to 4 nPartitions. See here:

http://docs.hp.com/hpux/hw/index.html#Server%20Expansion%20Unit

This would create other SPOFs, with the cable between the Server and SEU. The User Service guide seems to indicate only one cable. Also, the Board that the cable connects to would be the other.

-Josh
What are the chances...
Nico Schockaert
Trusted Contributor

Re: RP8400 SPOFs

Hello,
Today you can have 4 npars on the rp8400 :
"The new rp8400 Server Expansion Unit (SEU) is orderable as of September 8th. The 9U high SEU will double the number of rp8400 I/O slots from 16 to 32, the number of integrated discs from 4 to 8, the number of integrated removable media devices from 2 to 4, and enables the doubling of hard partitions from 2 to 4."
Hope this helps,
Nico