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* This Question and Answer was written for and applies to HACMP/6000 *
* Version 1.2. Similar function is possible with HACMP/6000 Version *
* 2.1, although the implementation specifics are different. *
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Configuration questions about more than two nodes with HACMP
Can I have more than two rs6k in High Availability Cluster
mode 1 or 2 ? I need 2 RS6k active in cluster and another one
to standby (backup) of each one, like this:
dual LAN interface Tree LAN inter. dial LAN interface
-------------------------------------------------------------------
| | | | | 9334-501 | |
1 active processor 9334-501 Backup ------ 2do.Active proc.
---------- ------ ---------- |2GB | ----------
|RS6k |dual Scsi |2GB | |RS6k | |----| |RS6k |
|7013-580|----------|----|----|7013-580|----|2GB |---|7013-580|
| |----------|2GB |----| |----|----|---| |
| | |----| | | |1GB | | |
---------- |1GB | | | ------ ----------
2GB ------ ---------- shared 2GB local
Local Disk Shared 2GB local disk Disk
disk disk
| |
| |
--------
|2gb |
|2gb | Local
|1gb | Disk
--------
I believe that I need DUAL LAN interface and DUAL SCSI
interface (two SCSI to connect rack 9334 and another one
to local disk attachment). I need 5GB in shared Disk and
additional 5GB disk for mirroring. I suppose that AIX and
swapping space are in local disk. Is it correct ?
If I need more active processors (3 active and 1 backup), is
possible to do with HACMP/6000 ?
ANSWER
Yes, the "Third-Party Takeover" configuration of Mode 2 allows you to
have 2 active servers, with an additional system to back either of the
servers up. I have modified your diagram as shown below to reflect a
viable TPT configuration for your needs.
dual LAN interface 3 LAN inter. dual LAN interface
-------------------------------------------------------------------
| | | | | 9334-501 | |
1 active processor 9334-501 | | | ------ 2 Active proc
---------- ------ | | | |2GB | ----------
|RS6k |dual Scsi |2GB | | | | |----| |RS6k |
|7013-580| |----| | | | +-|2GB |---|7013-580|
| |----------|2GB |--+ | | | | |----| +-| |
| |----+ |----| | | | | | |1GB | | | |
---------- | |1GB | | | | | | ------ | ----------
2GB | ------ | | | | | shared | 2GB local
Local Disk | Shared | | | | | disk | Disk
| disk | | | | | |
| 9334-501| Backup | ------ |
| ------ | ---------- | |2GB | |
| |2GB | | |RS6k |--+ |----| |
| |----| +-|7013-580|----|2GB |-+
+-----|2GB |----| | |----|
|----| | | |1GB |
|1GB | | | ------
------ ---------- shared
Shared 2GB local disk
disk disk
The backup system should have 3 network interfaces, so it can take over
for either or both of the primary servers. As for the shared disk, the
backup system must share disks with each of the primary servers. To
protect against disk drive failure as well as 9334 power supply, SCSI
adapter, and SCSI cable failures, the backup system should share 2 SCSI
buses with each server, with mirroring implemented across the shared
buses on each side. (I have configured 5 GB shared and mirrored on each
side...you can half this if your requirement is for a total of 5GB). You
are correct in that AIX and local paging space is on the local disks of
each system. Currently, HACMP is only able to support up to 2 active
servers and 1 backup.
An alternate, lower cost solution might be to use a Mutual Takeover
setup. In this case you have 2 active servers, each able to back up the
other. In a failure situation, the surviving server would carry the load
of both until the failed server was repaired, but it would save you the
requirement for the 2 extra SCSI strings you need in TPT. Please see the
HACMP Planning and Installation Guide (SC23-2409-03) for more information
on configuration modes.
S e a r c h - k e y w o r d s:
HACMP CONFIGURATION THIRD-PARTY TAKEOVER TPT
WWQA: ITEM: RTA000068009 ITEM: RTA000068009
Dated: 05/1995 Category: ITSAIHA6000
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