paging space

[aaronkeith]

hi! i need your expertise on this. i have RS/6000 F80 with 2 disks (one 18.2GB and 36.4 GB). The 18.2 GB (rootvg) contains the OS, informix and other applications. The 36.4GB disk will serve as datavg (almost all lvs are raw devices) for informix. The memory of the server is 2GB. Based on the paging space computation, the paging space that i need to configure is 2692 MB. What is the best way to configure the paging space? Should I put all of it on rootvg alone or should I split it into rootvg and datavg? If ever I will split it, should I configure it equally on both disk?

Please help me to find out the best way to configure the paging space.

Thanks in advance!

 

[Boria]

Hi,
I recomend you to do two pg each of 2gb of memory first on hdisk0, second on hdisk2. (do not ask me why).
Regards Boris

 

[Chapter11]

I disagree. My opinion is that paging space remain exclusive to rootvg.

Putting paging space in other volume groups makes it impossible to ever do vg-level operations on that volume group without reconfiguring and rebooting.

If your rootvg consists of multiple disks and you aren't mirroring it, then by all means, distribute it across multiple disks, but never put a paging space outside of rootvg.

My 2c.

 

[AIXSPadmin]

This link is for an IBM Whitepaper on paging space practice and policy that should answer your questions.

http://www.ibm.com/servers/aix/products/aixos/

whitepapers/pagingspace.pdf

 

[Astrotrain]

IMHO:

Keep the paging space on the 'rootvg' (hdisk0). That is the first load and mount.

Otherwise you may experience a system crash due to no or very little paging space for the system to work with while booting.

Also it is wise to keep the paging space on local hdisks. Do not throw them out onto a disk array unless you really have to.

 

[Yegolev]

when we have to put another wad (say 8-16GB) of paging out there, we usually have a "pagingvg" on a pair of disks that has just the paging00, and sometimes the mksysblv which just holds our mksysb image before archiving. we do this with internal disks as much as possible.

the only time i ever had a problem booting was when hd6 did not activate due to a bothersome bug upgrading to 4.3.3. then next time, i did some editing on the inittab which i should have done the first time, and it was better, even though it only had 512MB of RAM.

IBM Certified -- AIX 4.3 Obfuscation

 

[bi]

I don't think you can make a blanket statement about not putting paging space in any other volume group except rootvg.

The first paging space, hd6, of course, has to be on rootvg so the system can boot. But if you need to add paging space and you only have one disk in rootvg, you will take a performance hit if you put the second paging space on the same disk as hd6.

The IBM certification study guide says the only thing you have to worry about with paging space on non-rootvg disks is that the VG can't be varied off or exported without telling the system not to activate the paging space on boot and then booting the system.

I also don't see much harm in putting paging space on a disk array, as long as you know the disk is not part of a VG that will ever be exported or will be varied off. I once had a choice between putting paging on 2104 disks or SSA disks. I chose the SSA disks because they were a little bit faster.


aaronkeith said he has two disks, one in rootvg and one in datavg. He needs to add a paging space. It seems to me from a performance point of view, Boris is correct.

 

[Chapter11]

In a 2-disk config as originally described, I would create a single larger paging space, not split it between root and data.

If you can dedicate disks/vgs to paging, that's great. I'd love to, but I don't need that much paging space.

I do find it very odd to have 8-16G worth of paging on a 512M system.

 

[aaronkeith]

thank you so much for all the insights that you have given me. now, i know the advantage and disadvantages of putting it into 2 disks or confining it into one disk only.

again, thank you so very much for all the info. you really helped me a lot.

Sincerely,
aaronkeith

 

[khan99]

Hi Everybody,
I am a unix Sun Solaris Administrator. I am very comfertable with Solaris but now I am moving to a project that uses AIX and HP/UX. Could someone advise me as to what are the pros and cons of the move as far as administration of thse new boxes goes? Will it a major move for me and I will have to go though big learning curve or it will be alright? Also any books and trainging that you recommend?
All help will be greatly appreciated.
Best wishes

khan99

 

[bi]

khan, you might want to start a new thread rather than piggy back you question on this one.

But...

Were the Sun systems on Intel or SPARC?

I went the opposite direction: first HP-UX, then AIX and finally Solaris on a SPARC system.

The major difference for me was that Solaris didn't have the concept of volume groups and did have the concept of "slices". (I use DiskSuite, not Veritas, unfortunately.)

Like Solaris, HP has a lot of kernel parameters you can/must tweak. AIX has very few, but does have the vmtune command you can use to tweak performance.

HP's sam and AIX's smit are superior to admintool on Solaris. smit (or smitty for non-graphical terminals) is the best of the three and will really spoil you.

HP's sam has some limitations (or used to) in letting you precisely place filesystems on certain disks, so you have to learn the command line commands, but you get used to that. It used to be buggy in the 10.20 version, but I haven't noticed too many problems with 11.x.

I suggestion you mark this URL. It lets you look up the name of a command you are familiar with in Solaris and see what the command is in AIX or HP:

http://bhami.com/rosetta.html

The O'Reilly System Administration book is good because it talks about the different flavors of Unix and what the commands are and how they might differ slightly from one flavor to the next.

Go to

http://www.redbooks.ibm.com

and search on certification AND AIX. The certification guides have a lot of info on system administration on AIX.

HP either isn't as generous with their doc or I haven't found the right spot on their web site.

 

[dkieffer]

We run a similar setup using Informix and a rootvg and datavg. We did tests for performance having paging all on rootvg, split or all on the datavg. We found the best performance was when split between the vgs.

 

[anshudad]

You should always try to keep paging space in as many disk as possible but preferably equal sizes. But do not span it across disks. Also do not create more than one paging space in a single disk.
If you have two disks then by default hd6 is the paging space in rootvg. Increase it . Add another paging space in other disk.Preferably same size as hd6.

 

[aaronkeith]

thank you so much. I'll try to configure a paging space on my datavg. I haven't tested the p[erformance yet because we are still in the process on configuring our applications.

Again, thak you so much for the help.