ITEM: I5000L

hacmp questions




Question:

I have a model 520 with 3-670mb drives, 1 for rootvg, 2 for data.  I want to
setup a HACMP environment.
(1) can I use a 3xx series as the second machine?  what are the system requirements?
(2) what type of external disk do I need? 9334?
(3) do the terminals have to be ethernet or token-ring attached?  will async work?

I want to setup a minimum system.

Response:

(1) According to salesman there is no restriction in using a 5xx series
    with a 3xx series.  This is the only restriction on choosing:

  o   The POWERserver 7013 (500 series models) should not be coupled with
      POWERserver 7011 (200 series models).

(2) According to salesman here are the disk subsystems available:

  The following table shows each type of media, which adapter is available for  
  that media, which disk enclosures are available for that adapter and which
  disk drives and sizes are available for that enclosure.  ONLY these
  combinations are valid for HACMP/6000 Version 2.1.  SCSI-2 Differential or
  serial media is preferred wherever possible in place of SCSI SE media.

                                                              Max. \# of
                                                              Enclosures
    Type         Adapter  Enclosure   Disk        Size(GB)    per SCSI bus
    -----------  -------  ---------   ---------   --------   -------------
    SCSI-1 SE    2835     7203        2300/7203      .355          5
                                      2310/7203      .670          5
                          7204-320    2320/7204      .320          5
                          9334-500    2510           .670          1
                                      2530           .857          1
                                      2570          1.37           1
    SCSI-2 SE    2410     7203        2320/7203     1.0            2
                          7204-001     001/7204     1.0            2
    SCSI-2 Diff  2420     9334-011    2565          1.0            1
                                      2585          2.0            1
                          9334-501    2565          1.0            1
                                      2585          2.0            1
                          7135-110    2716          1.3            1
                                      2720          2.0            1
                          7204-215    2585          2.0            3
    Serial       6210     9333-010    3100           .857
                                      3110          1.07
                          9333-500    3100           .857
                                      3110          1.07
    Serial       6211     9333-010    3100           .857
                                      3110          1.07
                          9333-500    3100           .857
                                      3110          1.07
    Serial       6212     9333-010    3100           .857
                                      3110          1.07
                          9333-500    3100           .857
                                      3110          1.07
                          9333-011    3100           .857
                                      3110          1.07
                                      3120          2.0
                          9333-501    3100           .857
                                      3110          1.07
                                      3120          2.0

And here is the cabling required:

  Disk Cabling for HACMP/6000:

  For a given cable, any item listed in the "from" column can be connected to
  any item in the "to" column.  A serial bus can use any of the serial cables.  
  Serial bus cabling is not covered in the following tables.

    SCSI-1/2 SINGLE ENDED CABLING

                                                Len
    Feature       Type      From     To         (m)  Notes
    ---------  -----------  -------  --------  ----  ------------------------
    3130       SCSI-1 SE    7203,    7203,     0.66
                            7204     7204
    3130       SCSI-2 SE    7203,    7203,     0.66
                            7204     7204
    2915       SCSI-1 SE    Adapter  7203,     1.57  Passthru terminator
                            (2835)   7204            cable.  Withdrawn from
                                                     market.  Available as
                                                     RPQ \#8A0759.
    2915       SCSI-1 SE    Adapter  9334-500  1.48  Passthru terminator
                            (2835)                   cable.  Withdrawn from
                                                     market.  Available as
                                                     RPQ \#8A0759.
    2914       SCSI-2 SE    Adapter  7203,     1.57  Passthru terminator
                            (2410)   7204            cable.  Withdrawn from
                                                     market.  Available as
                                                     RPQ \#8A0758.

  The configurations in the following table assume that the two processors are  
  at the end of the bus (just prior to each terminator) and all the storage
  devices are connected to the bus between the processors.

    SCSI-2 DIFFERENTIAL CABLING

                                       Len
    Feature    From      To            (m)  Notes
    ---------  -------   --------     ----  --------------------------------
    2422       Adapter   2919,        .765  Y-cable; base to adapter, long
               (2420)    9334 cable,        leg to 9334 cable or 7135-110
                         terminator         interposer (2919), short leg is
                                            terminated
    none       Y-cable   self         0     Terminator, 50 pin, hi-density,
                                            included when the Y-cable is
                                            ordered.
    2921/2923  Y-cable   9334-011           2921 - 4.75 m
                                            2923 - 8.0 m
                                            8.0 m cable must be paired with
                                            the 4.75 m cable
    2921       Y-cable   7504-215     4.75
    2848       7204      7204         2
    2931-2937  Y-cable   9334-501           2931 - 1.48 m
                                            2933 - 2.38 m
                                            2935 - 4.75 m
                                            2937 - 8.0 m
                                            8.0 m cable must be paired with    
                                            a 4.75 m or shorter cable
    2919       Y-cable   7135-110     0     Cable interposer; connects 50
                         cable              pin Y-cable to 68 pin 290X cable
                                            for 7135-110
    2901-2914  7135-110  2919               Connects 7135-110 array
                                            controller to an interposer
                                            (2919)
                                            2901 - 0.6 m
                                            2902 - 2.4 m
                                            2905 - 4.5 m
                                            2912 - 12 m
                                            2914 - 14 m
                                            12 m and 14 m cables must be
                                            paired with a 0.6 m or 2.4 m
                                            cable
  The recommended 7135-110 bus configuration with only one 7135-110 is:
  o   Two controllers on the 7135-110; one active, one passive
  o   Connect the active controller to two processors
  o   Connect the passive controller to the same two processors

  This yields two different SCSI buses, one with both processors connected to
  the active controller and the second SCSI bus with both processors connected  
  to the passive controller.  The RISC software manages access to the different 
  controllers and will switch controllers (from the active controller to the
  passive controller) if the active controller fails; this occurs independently 
  of HACMP.

According to HACMP Planning and Installation Guide the only supported
media for concurrent access are the 7135 RAID unit, 9333 serial unit, and
9334 SCSI-2 DE unit.

The customer has several 670mb drives.  He should be able to use the 9334-500
with the SCSI-1 SE drives even though SCSI-2 DE or serial is preferred.

(3) The terminals need to be able to switch between hosts for crash recovery.
    There are serveral options (as listed by item Q606194 in ASKQ)

I can recommend three alternative means of getting asynchronous communication 
services failed-over in an HACMP/6000 environment:                                      

 1.  The first method uses IBM 3151s (or any other terminal that will           
     support the function) with the "Cartridge for Connectivity" option.        
     This option lets you connect the 3151 to two separate tty connec-          
     tions and "hot-key" between the sessions.  If each of these sessions       
     is on a separate machine, you can hot-key in the event of a failure.       
                                                                                
 2.  The second method is to switch at the adapter.  If you are using a         
     64-port adapter, you run four RJ-45 triple-twisted-pair connections        
     to four concentrators that are in turn cabled to your devices,             
     you could switch that cable between two adapters on different              
     systems.  In this way, either of the processors serve the term-            
     inals.  The switch is not available from IBM, but any number of            
     catalogue-style vendors would be glad to provide one to you.  An           
     improvement on this configuration is something we are working on           
     here at the Center with "Black Box".  We are in the process of             
     having them build a box that we designed that would switch the             
     RJ-45 connection electronically.  The command to switch would be           
     sent from the surviving machine in the cluster in a protocol defined       
     by the box, from a command executed as a part of the topchng.rc            
     script.  When this configuration is completed, we will post some           
     pricing information to this data base -- probably in a "HOWTO AIX"         
     pricing information to this data base -- probably in a "HOWTO AIX"         
     item.  In the mean time, if this method appeals to you, you might          
     ask Black Box or some other vendor to configure your connection            
     for you.                                                                   
     As for how the box would work, sometimes a picture is worth a thousand         
     words:                                                                         
                       ---------------------                                    
                       |  16-Port          |                                    
                       |  Concentrator     |                                    
                       ---------------------                                    
                         |                                                      
                         |                                                      
                         |--->|-----|                                           
                              | A-B |                                           
                              |-----|\<---                                       
                               |   |    |RS-232                                 
                               |   |    |                                       
       ------------            |   |    |   -------------                       
       | Mach. A  |            |   |    |-->| Mach. B   |                       
       |          |            |   |        |           |                       
       |          |            |   |        |           |                       
       |  64-port |            |   |        |   64-port |                       
       |     =====|\<-----------|   |------->|=====      |                       
       |          |                         |           |                       
       ------------                         -------------                                                                                                      
                                                                            
 3.  The last method is probably the most trouble-free, and more directly       
     responds to your need for a Token Ring connection.  A terminal server      
     essentially is a network client that is smart enough to manage tty         
     devices.  In almost all cases, terminal servers attach to Ethernet         
     networks -- not Token Ring.  I have only ever heard of one producer        
     of terminal servers that connects to Token Ring, but I'm afraid I          
     don't know what their name is.  I believe that they are an IBM bus-        
     iness partner.  Don't abandon hope, however.  An alternative approach      
     is to use a smart client that can attach to Token Ring and also to         
     async terminals.  An example of this would be our own 220.  Although       
     it is priced comparably to a terminal server (a bit more when you          
     consider the 64-port card and Token Ring adapter), it is much more         
     powerful, working with a full-featured operating system.  This is          
     particularly valuable with HACMP, because it will allow the Cluster        
     Information Services (CLINFO) daemon to run without porting.  Once         
     you configure IP Address Takeover, clinfo will purge the client's          
     ARP cache so that the takeover machine resumes communication rel-          
     atively transparently.                                                     
                                                                                

IBM does not currently (4/19/94) make a terminal server.  In choosing a
terminal server (according to HACMP Planning and Installation Guide) you
need to consider:

1.  Can you update the terminal server's ARP cache?  The terminal server must
    comply with the TCP/IP protocol, including telnet.  If you will have
    modems for dial-in users, it must also support SLIP.

2.  Is the terminal server programmable, or does it need manual intervention
    when a cluster event happens?

3.  Can you have a control file from the cluster node to the terminal server
    that updates/handles cluster events' effects on clients?

If your terminal server does not meet these guidelines, you should choose the
Hardware Address swapping option when configuring the cluster environment.

Other considerations are summarized in question Q605036 on ASKQ:

 QUESTION:                                                                      
 If I plan to install HA/6000 and run in mode 1 (standby) must                  
 I license two copies of HA/6000 (one on the primary Risc machine               
 and one on the standby machine)?                                               
 2. Must I use two Ethernet adapters or does two adapters                       
 allow me backup for my network should it go down?                              
 3. Since the application is critical I plan to suggest mirroring.              
 Can I mirror the 9333 disk drive with another?                                 
 4. I would like to recover from a Risc System/6000 failure as quickly          
 4. I would like to recover from a Risc System/6000 failure as quickly          
 as possible. What hardware should I recommend? I am considering 9333           
 versus 9334 (SCSI). I am also looking into high speed fiber between            
 the two Risc Systems. Would the fiber improve takeover time or is the          
 takeover time just dependent on the scripts and the takeover tasks?            
 Regarding \#2 above do I need to wire two distinct lans for network             
 redundancy? What terminal servers are recommended to facilitate                
 moving to the second Risc System in case of failure of the primary?            
                                                                                
 ---------- ---------- ---------- --------- ---------- ----------               
 A:  1) You will need to buy one HACMP/6000 license for each machine            
        that will be run the HA server code.                                    
                                                                                
     2) In order to have network redundancy, you will need to wire two          
        separate LANs and have a minimum of two network adapters per            
        separate LANs and have a minimum of two network adapters per            
        machine.  This will insure single point of failure protection.          
                                                                                
     3) Yes, you can mirror a 9333 with a second 9333.  You can also            
        mirror the disks internally within a 9333.                              
                                                                                
     4) The 9333 is a better choice than the 9334 as far as recovery            
        time.  Purchasing a fiber link is probably a waste.  Most of            
        the time during recovery is during the configuration on the             
        backup server.  Fiber might be a couple of milliseconds faster          
        in determining a fault with the primary server.                         
                                                                                
     5) You could use a 220 as a terminal server.  This would allow you         
        to run clinfo so that the 220 would automatically switch over           
        when the primary server failed.                                         

Customer had more questions on HACMP:

(1) Does HACMP takeover immediately after failure?  How does it do it?
(2) Can I have something else on the SCSI bus besides the 9334-500?
(3) What type of ethernet requirements do I need?

Response:

Called Jeff Grubb to get more information.  The 9334-500 requires a \#2835
scsi adapter for each machine.  It also requires a scsi PTT cable which
is available as an RPQ \#8A0759.  

(1) When the primary server goes down HACMP allows the 2nd backup to switch
    ip addresses with the primary, remount all the filesystems, mount any
    nfs filesystems, and reinitiate a getty to all terminals within 
    30 - 300 seconds.

    In addition, HACMP can be setup in a type of mutual takeover that
    will allow you to run secondary applications on the backup machine.
    In the event of failure all applications would be run on the backup.

(2) The 9334 can be the only device on the bus.
(3) You will need two ethernet controllers for each system.  One to connect
    to the network and one to connect between the two machines.  

There is a publication that can tell you more about HACMP capabilities.
It is publication SC23-2595 - HACMP System Overview.


Support Line: hacmp questions ITEM: I5000L
Dated: April 1994 Category: N/A
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