need advice on AIX virtualization


 
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Operating Systems AIX need advice on AIX virtualization
# 8  
Old 06-03-2011
Gozillion thanks, it's impossible to overestimate the luck of meeting real experts who can explain things in a simple language. God bless this forum :-)

May I ask couple more questions on this:

1.
Quote:
Originally Posted by bakunin
If we talk about virtualisation we usually understand it the way it is done in i.e. Linux: you start with a (physical) machine, where you install some OS. In this OS you start some program, which emulates a some virtual hardware. On this hardware you install another OS and start an application on top of that.

Virtualization in p-Series systems is different from that concept, because the base OS (which would run on the physical machine above) and the emulation program are missing - their functions are done in the systems hardware directly.
Clear now. I can guess that productivity of p-Series-type virtualization is better, since there are less layers of software.

But what are the drawbacks of p-Series-type virtualization? What are there things that first type of virtualization can do, but p-Series type of virtualization cannot do?

2.
Quote:
Originally Posted by bakunin
You may even - depending on some details in your environment i don't know - be able to "live-migrate" your LPARs from one system to another, which means as much as moving them from one big box to another big box without even shutting them down
Hmm... You're saying that I can (in principle) move my app (and its LPAR) from box to box easily. And can I (again, in principle) at all decouple my app and my boxes? I.e. have a bunch of IBM boxes and some "hyper-LPAR" that aggregates all of them into one big machine? And my app that runs on that "hyper-LPAR" and doesn't really care whether it in reality executed on box A, box B, or even both boxes A and B? Do people do that?

Thx again

---------- Post updated at 02:39 PM ---------- Previous update was at 02:38 PM ----------

Quote:
Originally Posted by zxmaus
If you have 2 rootdisks and maybe a uat or test or dev system running your applications, do an alt_disk_install (clone the system), try to test-migrate on the existing hardware to 6.1 and see how your applications deal with this change. In our environment we have updated a huge amount of systems running all kinds of applications from AIX 5.2/5.3 to 6.1 and only one application had issues with 6.1 and required a reinstallation on the new platform to run properly.
AIX usually does a pretty good job in being downwards compatible so you might be lucky ...
Regards
zxmaus
Thanks, I'll check with IT team. That's a super hint!
# 9  
Old 06-03-2011
But what are the drawbacks of p-Series-type virtualization? What are there things that first type of virtualization can do, but p-Series type of virtualization cannot do?

The only drawback for IBM virtualisation would be if you are running an emormous Oracle database. This LPAR could benefit from dedicated fibre adapters to connect to its own external storage. However the industry standard now is to provide 4 VIO servers per frame. These are further split into one pair providing networks and the other pair providing storage. The use of NPIV (Virtualised Fibre Adapters) also helps with the write and read latency.

I feel you should stop thinking of the AIX environment as a virtualised system along the same lines as a VMWARE system residing on host system. The IBM virtualised system is a large number of seperate AIX machines sharing CPU and memory resources with I/O being supplied via the VIO server.

Also what ZXMAUS has said is quite acceptable but even if you are dealing with a lowly P520 (P720) you would have enough power available to build two VIO servers and a couple of LPARs. One LPAR could provide your running production environment with AIX 5.3 and you apps installed. With the second LPAR having either AIX 6.1 or 7.1 installed as a development system to check the stability of the APP in the newer environment. Neither system would know or interfere with the other!

Hmm... You're saying that I can (in principle) move my app (and its LPAR) from box to box easily. And can I (again, in principle) at all decouple my app and my boxes? I.e. have a bunch of IBM boxes and some "hyper-LPAR" that aggregates all of them into one big machine? And my app that runs on that "hyper-LPAR" and doesn't really care whether it in reality executed on box A, box B, or even both boxes A and B? Do people do that?

Why would you want to? How will it share resources? AIX 6.1 and 7.1 both support "Live LPAR Mobility" which enables an LPAR to be moved to another LPAR in a frame, or between two different frames. There is really no such thing as a "hyper-LPAR". The only thing which would allow what you are describing is HACMP or Veritas Cluster Manager (VCM).
# 10  
Old 06-03-2011
Many thanks - a consultant actually listening to what technicians have to say is balm on the tortured soul of the latter. ;-))

Quote:
Originally Posted by Irishango
Clear now. I can guess that productivity of p-Series-type virtualization is better, since there are less layers of software.

But what are the drawbacks of p-Series-type virtualization? What are there things that first type of virtualization can do, but p-Series type of virtualization cannot do?
This is a bit tough to explain: basically there are two concepts of virtualization, called "full virtualization" and "para-virtualization". What i have described in my last post as "Linux-type virtualization" is in fact "full virtualization": The OS of the virtual machine is not aware that it is virtual at all. If, for example, the disk driver has to write some data to the disk it would write to the standard interfaces like there would be a real disk. Only then the underlying program in the host OS would intercept this, decode it, then create some real disk operation out of it and execute that. In "para-virtualization" the disk driver "knows" that it is only virtual and therefore would do a lot less, skipping tasks a real disk driver would do (because this would be done by the real driver anyways).

Paravirtualization is virtualization with virtual systems which are aware of their virtuality status. It is obvious that paravirtualization needs a lot less reources, hence is "more productive" than full virtualization - the "price" being that you need these paravirtualized software layers (network drivers, disk drivers, filesystem layers, etc.).

To come back to your question: the "drawback" of p-Series virtualization is its limited scope: you can only have AIX or Linux as OS of an LPAR. Compare this to VMWare, where you have *some* host OS (Windows, Linux, ....) and some (or even several) guest OS(es): Linux, Windows, BSD, ....

On the other hand there are paravirtualized environments in Linux too: OpenVZ, for instance, kvm (which is in parts paravirtualized), ... What exactly the "performance per unit of money" is in these systems is hard to tell - when you calculate the TCO of a system in the data center there are so many aspects - hardware cost, power consumption, footprint (space is a limited resource in data centers), service level of hardware support, etc., etc.. - that "virtual systems served per processor" or something such only plays a very limited role.




Quote:
Originally Posted by Irishango
Hmm... You're saying that I can (in principle) move my app (and its LPAR) from box to box easily. And can I (again, in principle) at all decouple my app and my boxes?
In fact this was one of the expressed goals of this system. It is called "Live Partition Mobility" (you can google this term) and there is an IBM redbook about it, in case you are interested in the gory technical details:

RedBook on Live Partition Mobility

Quote:
Originally Posted by Irishango
I.e. have a bunch of IBM boxes and some "hyper-LPAR" that aggregates all of them into one big machine? And my app that runs on that "hyper-LPAR" and doesn't really care whether it in reality executed on box A, box B, or even both boxes A and B? Do people do that?
Not that way, but the other way round: You have a big box A with LPARs A1, A2, A3, ... A10 and a big box B with LPARs B1, B2, ... B10. You can (if resources allow this) now move partition B1 so that its definition (the part on the HMC which says how much memory, processors, ...) is transferred, the running system is also transferred to box A and - this is the real clou ! - even the virtual disks and network adapters, which were served by the VIOS on box B are transferred to the VIOS on box A. All this can be done while the B1 system is running and under load.

There are a few considerations for the procurement of hardware though: to be real flexible you need as big systems as possible, because you can divide and distribute your resources inside but not outside. If you want to create an LPAR with 10G of memory but have 5G left in box A and another 5 in box B you are stuck. This means instead of many small you better have few big systems for maximum flexibility.

(Corollary: this is why Blade Centers are a real bad idea when you want to do virtualization - you better use 3 p570-(p770)-systems instead of 3 Bladecenters full of small units.)

On the other hand, every hardware breaks sometimes. That means you have to choose your hardware small enough that you can easily make one free so that you can perform maintenance on it. If you have only two very big boxes they will have to be big enough to take all the LPARs from the other one once you do maintenance on one of them and making them double as big as necessary can be costly. If you have 10 smaller boxes instead it is a lot easier to make one free to undergo maintenance, because its LPARs can be distributed over the remaining 9.

I hope this helps.

bakunin

Last edited by bakunin; 06-03-2011 at 01:29 PM..
# 11  
Old 06-05-2011
Thanks a lot, colleagues! Greatly appreciated.
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