Originally posted by: klimenta

Hi,

we are running AIX 5.2-09-04 on p660 server. This server contains 2 x 18Gb internal mirrored drives and 8 external hard drives (ExpPlus 2104-DU3 hdd rack).

rootvg is on both internal (hdisk0, hdisk1) drives. hd6 paging LV is on rootvg.

I am trying to install some DB2 fixpack but I don't have enough space in /usr.
/usr is also in rootvg.

I bought two external hard drives for the rack but as far as I understood I can't expand /usr on external hard drives. Right or wrong?

If I can't go with the above solution, I was thinking about this. Moving the paging space with migratepv -l hd6 hdiskX where hdiskX is my new external hard drive. Can I move paging space on external hard drives?

If this is possible, then I'll use the old paging space which is on rootvg and assign it to /usr.

And if the above is not possible too, how about this. I'll decrease my current 8Gb paging space to 7Gb and give that extra 1Gb to /usr. This shouldn't be a problem, because this is a test server and lsps -a shows only 8% use anytime.

Below is some output from the server.

Thanks for any input on this

(root)@eia2: />lslv hd6
LOGICAL VOLUME: hd6 VOLUME GROUP: rootvg
LV IDENTIFIER: 000fa79fe20457ee.2 PERMISSION: read/write
VG STATE: active/complete LV STATE: opened/syncd
TYPE: paging WRITE VERIFY: off
MAX LPs: 512 PP SIZE: 32 megabyte(s)
COPIES: 2 SCHED POLICY: parallel
LPs: 272 PPs: 544
STALE PPs: 0 BB POLICY: non-relocatable
INTER-POLICY: minimum RELOCATABLE: yes
INTRA-POLICY: middle UPPER BOUND: 32
MOUNT POINT: N/A LABEL: None
MIRROR WRITE CONSISTENCY: off
EACH LP COPY ON A SEPARATE PV ?: yes
Serialize IO ?: NO

(root)@eia2: />lsps -a
Page Space Physical Volume Volume Group Size %Used Active Auto Type
hd6 hdisk0 rootvg 8704MB 8 yes yes lv
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Originally posted by: hwyguy

Moving Paging and/or /usr to external disk - while totally possible - is generally a bad idea, as you're introducing another point of failure into your system. If the external storage goes - so does your server.
If you're sure that you never use more then 7 GB of paging (and if you did, that would be a problem in its own right!), then I think your best bet would be to decrease your paging space by 1 GB and give that to /usr.
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Originally posted by: klimenta

I am trying to figure out, why extending rootvg with external hard drives is a bad idea. I'll use 2 mirrored hard drives that are hot-swappable. If something goes wrong with the external drives it is easier to replace external hot swappable hard drives than internal. Or is there something that is a drawback using ext. hard drives for rootvg?

Thanks
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Originally posted by: bassemir

How about adding both external drives to the rootvg volume group. With the two drives added I think you could still mirror rootvg and then have additional space in rootvg for /usr.

Rich
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Originally posted by: klimenta

That looks the easiest way of doing the upgrade. Put the external hard drives, extend rootvg, increase /usr. No reboots, no nothing and in 5 minutes i'll have my server ready. But is this the right way of doing it? That's wy I am concerned.

Thanks
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Originally posted by: hwyguy

There's no "wrong" way of doing it - just different ways

Again, the only thing you're negative I see by going external with rootvg is introducing more points of failure into your system. If it's mirrored, all the better - but still you run the risk of the enclosure failing or a cable, or card going south. And if /usr or paging is on that external array - bye bye Mr system.

Decreasing your paging space is also just as easy - 2 commands, no reboot required:

1.) Decrease your paging by 1 GB: chps -d 32 hd6

2.) Increase /usr by 1 GB: chfs -a size=+1G /usr

Message was edited by: hwyguy - removed a ' from chps -d
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Originally posted by: klimenta

I talked with IBM support and they didn't recommend extending rootvg on external disks, because I'll have inconsistent mirror. It is possible, but they won't give support if something goes wrong with this type of setup.

I also asked them if I can move paging space completely to external drives. The support guy wasn't sure about this and he said that he doesn't know if this will work, so it is not recommended.

So, my only solution is to decrease the paging space.

Thanks
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Originally posted by: SystemAdmin

You should always have some amount of paging space in rootvg; AIX installs usually set hd6 to 512 MB. I would suggest decreasing the size of hd6 by some quantity. You would then add an additional paging space equal to the resized hd6 and locate it in a different volume group to give you the same or more paging space than before. Ideally, you would want to have this new paging space on a different set of disk spindles. AIX would automatically split the paging usage between the 2 areas which would also improve paging performance.

An example would be:
hd6 4096 MB rootvg
paging0 4096 MB VOLGRP1

You would need to make sure that paging space "paging0" is set to automatically activate when the system is started.

You should also check to see if you have any AIX fixes which are still in the APPLIED state. Committing them would also free up space in /usr. Also, check for third party applications which might be writing logs and temporary files in /usr. For example, Symantec (Veritas) NetBackup installs in /usr/openv and writes log files in one or more subdirectories of /usr/openv.
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