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Moving RAMs(memory DIMMs) from one rx6600 to another

 
Ramaprasad K
Regular Advisor

Moving RAMs(memory DIMMs) from one rx6600 to another

There is a requirement to move Physical memory from one rx6600 to another. Following is the current scenario:
-> 2 rx6600 servers
-> First server with 32 GB mem. and Second with 24GB

New requirement is to move 8GB RAM from First Server(with currently 32GB) to Second Server(with currently 24GB) so that new config. becomes:
-> First server with 24GB and Second server with 32GB.

Can anyone clarify me on few of my queries:
1) Can I do this or to put it in other way, Is it possible to do such a movement?
2) What precautions should I take before I go ahead with the activity?
3) Is it as simple as reducing mem (and correspondingly SWAP space) in First server and adding mem. in second(corres. increasing SWAP space) ?
4) Any patces, F/Ws...??
5) What activities after moving the memory?

Thanks in advance,
Ram
9 REPLIES 9
Udo Werner
Occasional Visitor

Re: Moving RAMs(memory DIMMs) from one rx6600 to another

Hello Ram!

You should first of all check which type of memory carrier and what type of DIMMs are installed in the servers.

Keep in mind that the rx6600 can have two different types of memory carrier (24 Slot and 48 Slot).

You can check that with STM -> Info!
or
with the output of the MP command DF (Display FRU).

Regards,
Udo

Re: Moving RAMs(memory DIMMs) from one rx6600 to another

Hi Ram!

No problem, you can move those 8GB assuming your 32GB source system doesn't need them! That's probably the main issue regarding the source server. You can check that by running the top command when your server is running a normal workload, peak workload if you want to be 100% secure. Look at the Free Mem value, that should be 8GB minimum. If so, no problem, you can make that swap. Else, take care, your users will probably experience some perf decrease... Once you've removed that memory, I wouldn't do anything more than reboot it. Don't change your swap size, your system will just be "swap confortable", but he never complains about that...

Then move the mem modules : Shut both servers down, unplug their cords, open their case, don't forget your antistatic kit!!! and make the module exchange. Restart the source server, verify during the POST that it's now set to 24GB, and then let it go.
Then restart your destination server, also check the POST messages and verify it now has 32GB. If so, fine, else interrupt the boot sequence and shut it down again! You might have inserted the boards in wrong mem slots. This is explained on the server case maintenance sticker I guess. When you finally get it set to 32GB, restart the server. You don't have any patch or f/w update to apply, just increase the server swap space. The correct ratio is something like 1,5 x physmem size if I'm correct, therefore I would suggest you add a volume of 1,5 x 8 = 12GB for extra swap.
I don't think of any other thing to do then...

Best regards,

Pascal.
TTr
Honored Contributor

Re: Moving RAMs(memory DIMMs) from one rx6600 to another

Answers tio your questions
1) Yes
2) Check that you have enough empty DIMM sockets in the second server. Use the STM utilities. IMPORTANT: The memory DIMMs are installed in quads, that is in sets of 4 DIMMs each. So you need to determine how many DIMMs you will have to move from the first server and if you have enough empty DIMMs in the second server.
3) Yes. There are no settings that you need to change for the memory itself. The reduction and increase will become efective automatically. You don't have to reduce the swap space in the first server. As for the second server it depends on your process mix and the current utilization of the address space.
4) Usually no patches or F/W are involved in memory adding and reducing.
5) Monitor the memory and swap space utilization of the second server and increase the swap space if needed.

PS. Udo deserves more than 2 points for his answer. He preety much gave you a good summary of what you need to do.
Ramaprasad K
Regular Advisor

Re: Moving RAMs(memory DIMMs) from one rx6600 to another

Thanks all for your reply.
I am sorry, I gave Udo only 2 points(I want to give him more, is there any way i can do that? pl suggest).

1)I knew about checking the compatibility of Mem. extender boards(24 DIMM and 48 DIMM), but was not sure of what might induce some unforeseen effects after removing Mem from 1st Server(I presumed that some Kernel Parms or Applications assuming 32GB but after removal and reboot, if they see only 24GB, won't they panic). Anyway, I took the risk and went ahead.

2) I had run nickel script and checked all compatibility issues from part nos. Also, checked about free slots.

3) Thanks TTr for your ans to this qtn. And now my query is, is it possible to reduce the swap already being created as a 'dev' type? As this would free up some space on Local Hard disk. Is swap space something like virtual mem. concept in OS? Thanks Pascal for throwing light on Swap space. I want to know, on what basis did you decide for Swap space to be 1.5 times Phy Mem.? Till now, I followed the thumbrule of 2 times Phy Mem.

4) My main worry was on this and fortunately, due to time constraint, I didn't do any F/W upgrade or apply patch. would it have affected in anyway? As of now, at ground zero, it hasn't !!!!!

5) Thanks TTr again on this. Is there any tool to find out Mem or Swap utilization? Or is 'swapinfo -atm' command sufficient to know the utilization?

For your inforamtion, I completed the above activity on 9th May. Due to some other workload, could't update here. The activity went on successfully without any hiccups.

Regards,
Ramaprasad K
Dennis Handly
Acclaimed Contributor

Re: Moving RAMs(memory DIMMs) from one rx6600 to another

>I gave Udo only 2 points(I want to give him more, is there any way i can do that?

Only if he provides another reply.

3) >is it possible to reduce the swap already being created as a 'dev' type?

Yes but why? If you removed memory you may need more swap space.

>Is swap space something like virtual mem. concept in OS?

Yes.

>I followed the thumb rule of 2 times Phy Mem.

He just has smaller thumbs. :-)

>5) Is there any tool to find out Mem or Swap utilization? Or is 'swapinfo -atm' command sufficient to know the utilization?

Well, you can use swapinfo -tam to get the general picture. If you purchase glance, you can see in more detail. You can vmstat(1) to see of you have a lot of pageouts (po).

Ramaprasad K
Regular Advisor

Re: Moving RAMs(memory DIMMs) from one rx6600 to another

Very funny Dennis, I like that :-)

>>3) >is it possible to reduce the swap already being created as a 'dev' type?

>Yes but why? If you removed memory you may need more swap space.

I didn't get why I would need more swap space when I remove memory. If I had 32 GB Mem and swap space of 64GB, and I reduce to 24GB Mem, I would obviously require 48GB swap space. so, my query was if I can release that extra 16GB ,resereved and unused , for my data or applications.
Dennis Handly
Acclaimed Contributor

Re: Moving RAMs(memory DIMMs) from one rx6600 to another

>I didn't get why I would need more swap space when I remove memory.

The total swap is the sum of pseudo-swap and device swap. When you removed memory you reduced the pseudo-swap.

>If I had 32 GB Mem and swap space of 64GB, and I reduce to 24GB Mem, I would obviously require 48GB swap space.

It depends. If you are just blindly using your thumbs, you might think so. :-)

>my query was if I can release that extra 16GB, reserved and unused, for my data or applications.

It depends on how much swap space you were using before you removed the memory.
If less than 24+48, you can. If between that and 32+64, you can't, unless you reduce the number of applications running at the same time, to reduce the VM requirements.
Ramaprasad K
Regular Advisor

Re: Moving RAMs(memory DIMMs) from one rx6600 to another

Thanks everyone for your enlightining replies. Specially Dennis for his witty answers and TTr for his suggestion to assign more points to Udo and Pascal for his detailed explaination and especially Udo, i'm sorry if I hurt you by assiginig less points (in fact this is my first question on this Wonderful platform),for his immediate reapionse.

Thanks all again.

Closing this thread.

Regards,
Ramaprasad K
Ramaprasad K
Regular Advisor

Re: Moving RAMs(memory DIMMs) from one rx6600 to another

The activity was carried out by me without any hiccups. Only thing what I feel someone to ensure, in case they come across such challenge, is to ensure sufficient swap space in new server and to keep in mind of 'swchunk' Kernel Parameter ('maxswapchunks' in case OS is 11i v1 and below).

Feel free to directly contact me in case anyone needs any relevant docs.

Regards,
Ramaprasad K