[Server-devel] Suggested redundancy config

[Tony Pearson]

Greg wrote:
>That brought to light a couple of cases where we don't have a good plan:
>- Squid box failure.

Greg,
I have a radical idea, and it fits in the N+1 redundancy.  For OLE-Nepal, 
have three machines:
1) The primary XS
2) The primary Squid
3) The backup machine

Now, here's the trick, we make the "backup machine" have both an XS and 
Squid implemented on them,
and with scripts activate one or the other so the next time it starts up, 
that is what it runs as.  This simplifies
the recovery to:
XS goes down --> tell backup machine to be "primary XS" and reboot machine 
(with correct IP addresses)
Squid goes down --> tell backup machine to be "primary Squid" and reboot 
machine (with correct IP addresses)

The primary XS and Squid boxes can be scripted to send updates to the 
backup box, so that when it
needs to play one or the other role, it will have all the latest data.

In the event XS goes down and is replaced by the Backup box, then when the 
repaired XS comes back,
it becomes the new backup box.

This also supports "scheduled/planned maintenance", putting in a bigger 
drive, adding memory, etc.
One machine can be upgrade while the other two are getting the job done.

While the Squid box may not need as much memory or processor as the XS 
box, perhaps it would 
be simpler just to have a standard HW config for all three boxes so that 
they are interchangeable.  The
alternative would be to put the weakest box as Squid, strongest as primary 
XS, and the third is Backup.






Tony Pearson
Senior Storage Consultant, IBM System Storage?
Telephone: +1 520-799-4309 |  tie 321-4309 |  Cell: +1 520 990-8669
email: tpearson at us.ibm.com |  GSA: http://tucgsa.ibm.com/~tpearson
Blog: http://www.ibm.com/developerworks/blogs/page/InsideSystemStorage 
AKA: 990tony Paravane, eightbar specialist 


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