Required paging space recommandations on AIX5.3


 
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Operating Systems AIX Required paging space recommandations on AIX5.3
# 1  
Old 11-12-2013
Wrench Required paging space recommandations on AIX5.3

Hi Guys,



Can some one help me on what is the recommended (SWAP) Paging space required.

Below are the details of my environment
Currently The OS version AIX5.3

PHYSICAL RAM 32 gb

Because the page space is going high

Thanks
Murali
# 2  
Old 11-12-2013
I would worry what is consuming your memory first:-
Code:
ps -el | sort -n +9

Highest consuming process at the bottom. Process ID is third column.

The general rule of thumb was always double memory but I've heard more recently it should be 4 times, but at your allocated memory size, that's getting quite large. There is no fixed rule. You can add as much as you have disk space for pretty much.

I would suggest a volume group just for paging LVs though. Keeping it out of rootvg will improve performance (assuming that the disks are sensible) because of rootvg contention. Similarly, you don't want it on your application or data disks.

Keeping only a minimal hd6 will give you more chance of recovering a mksysb too. If you put huge paging LVs in rootvg, you must be able to accommodate them (and any mirror) on your DR server.



Have a measure of paging activity too. Something like vmstat 10 will give you a good report of how much reading and writing you are doing. If it's high, this will affect performance, so you are looking at real memory to alleviate that. Search out the high memory users first though.

We had an issue where code was firing up another module based on a user request and then no freeing memory at the end. The on-line users had huge allocation by the end of the day as they used each function. Our programmers found how to de-allocated memory when it was not required and the performance boost was very impressive. The cost of re-reading code was far less than the strain on the machine with all the paging.





I hope that this helps.


Robin
Liverpool/Blackburn
Uk
# 3  
Old 11-12-2013
Thanks a lot for reply

topas is showing

Memory Real, MB 32768

Paging space size,MB 6144 ,used 81%

please let me know ,Is the above configuration is good or do i need to increase the pageing space.

I found the some my internal database and applications are using
# 4  
Old 11-12-2013
Ouch! You have 6Gb paging for 32Gb real memory.

For 32Gb memory, I would suggest starting at around 128Gb paging. Do you have the space for that? If you allocate it in a few large chunks, then you will be better able to adjust it later, rather that 128 x 1Gb LVs or 1 x 128Gb LV.

Is your server suffering from no-memory and getting failures?

Have a look with errpt -a | more which shows the most recent issues at the top. There may be comments about dump space, swap/page space exhaustion along with full filesystem alerts and hardware failures.


You seem to have lost the end of your post. What else were you about to say?



Robin
This User Gave Thanks to rbatte1 For This Post:
# 5  
Old 11-12-2013
I rather differ with rbattel here,
I would say go with 32 Gigs of swap space.

Also, what server is that? DB or APP?
# 6  
Old 11-12-2013
It's only a suggestion and open to adjustment as murali969 sees fit, also hence why (s)he should create several paging spaces to meet the needs, so they are flexible. The real issue is whatever is using all that real memory.

I haven't got anything that big available to me because we do everything on the super cheap for hardware and pay the price in performance and upgrades later.




Robin
This User Gave Thanks to rbatte1 For This Post:
# 7  
Old 11-12-2013
Sorry, but I do not agree with such large Paging Spaces at all.
You don't want your application to use Paging Space since it will be really slow and will decrease the performance of your application considerably up to uselessness.

The old factors to size Paging Space do not fit anymore today at all.
For now 6 GB should be ok - you need to find out why your box is paging at all. There is some things you can tune on the behaviour how the Virtual Memory Manager (VMM) behaves when checking for the rate of RAM being used for file caching and for process data.
The other problem you could be, that you have a memory leak somewhere and that could be the reason you are running out of RAM and so it starts paging after some time.

For a start, please post the output of the following commands and use [code] and [/code] tags when doing so:

Code:
oslevel -s
vmstat -vs
vmo -x| grep -iE "minperm|maxperm|lru_file|poll"
svmon -G

## Have no AIX 5.3 at hand - I hope the syntax is still the same
svmon -P | awk '/Pid C/ {h=$0; next} NF == 9 && /^[0-9]/ {if($5 != 0) l[c++]=$0} END{print h; for(x=0; x<c; x++){print l[x]} }'


Last edited by zaxxon; 11-12-2013 at 12:18 PM.. Reason: added stuff, typos
These 3 Users Gave Thanks to zaxxon For This Post:
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