AIX extend VG error


 
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Operating Systems AIX AIX extend VG error
# 8  
Old 04-10-2019
Quote:
Originally Posted by Phat
I copy here again. Note that below info is taken from another machine which has big VG and scalable VG.
Big VG it has 2 parameters: Max PPs per VG and Max PPs per PV
OK, now i understand what you mean - sorry, my bad.

Yes, big VGs have still a limitation of how many PPs can reside on a single PV AND they have a restriction of how many PVs can be in a VG, although these limits are higher than in a classic VG. The scalable VG only has one upper limit and that is the number of PPs overall, in the whole VG. There is no limit of how many PPs can be in a single PV any more. You can set the maximum number of PPs for the whole VG at the creation of the VG and my suggestion is to set it to the maximum possible of ~2 million PPs as i told you already.


Quote:
Originally Posted by Phat
Like you said, we can increase LUNs in size at storage by adding 1 or more disks to the LUN.
ahem, no. A "LUN" consists already of many disk snippets (that is done inside the storage box) but it is presented as a single homogenous disk device to the OS. You can make such LUNs bigger (at least with certain storage systems) and this will - to the OS - look like the hard disk it has attached just grew in size. You do not "add another disk" or something such. To make use of such a grown disk first run cfgmgr to make the OS aware of the new size, then run chvg -g to make the LVM aware.

Quote:
Originally Posted by Phat
I have 1 concern here, currently, the max PP of PV is limited at 2032 PPs x 128 MB = 260 GB. Because of this limitation, I cannot add the 1 TB PV whose PPs are greater than 2032 PPs.

If we grow the LUN in size example 500GB in total, it will breach the limits of 2032 PPs. Still acceptable from VG side?
This is why i told you to recreate the VG: a PP size of 128MB is just ridiculous. Do yourself a favour and when you recreate the VG select a PP size of 1GB or even 2GB. I mean, is there any chance you may want to change (increase or shrink) a filesystem on that VG in steps smaller than 1GB? Certainly not, i'd reckon. Therefore there is no reason to have such a small PP size at all.

Such a recreation of the VG (and the filesystems it contains) will give you the opportunity to rectify the filesystems too: if you still have JFS filesystems recreate them with JFS2, if you still use external log volumes change the new FSes to use inline logs.

I hope this helps.

bakunin
This User Gave Thanks to bakunin For This Post:
# 9  
Old 04-10-2019
Hi Bakunin,
Quote:
Yes, big VGs have still a limitation of how many PPs can reside on a single PV AND they have a restriction of how many PVs can be in a VG, although these limits are higher than in a classic VG. The scalable VG only has one upper limit and that is the number of PPs overall, in the whole VG. There is no limit of how many PPs can be in a single PV any more. You can set the maximum number of PPs for the whole VG at the creation of the VG and my suggestion is to set it to the maximum possible of ~2 million PPs as i told you already.
So we can convert it to scalable VG and then we can add the 1 TB disk later?

Regarding the PP size yes it's ridiculous, it was created by the ex-admin and now I inherited all the legacy Smilie
# 10  
Old 04-11-2019
Quote:
Originally Posted by Phat
So we can convert it to scalable VG and then we can add the 1 TB disk later?
NO!! Again, for the umpteenth time now: you SHOULD NOT - even if you can!! You should recreate the VG on as few as possible LUNs, create new filesystems, then restore the contents of the old filesystems to the new VG, then delete the old VG, then remount the FSes. If you add another "1TB disk later" you will then have 30 disks in the VG (instead of the already 29 that are in it). This is unmanageable in the long run (and even on short term). Instead of learning ways how to more effectively use a crutch you should consider learning how to walk.

Of course you can do whatever you want, but ask yourself: does it make sense to even ask if you are going to disregard what you are being told anyways?

I hope this helps.

bakunin
# 11  
Old 04-12-2019
Hi Bakunin,

Understand your recommendation. My aim is to know if we can go this way technically Smilie
For the current status, there is no need to add new disk to that VG, we just need to create new VG and that's all. The scalable VG with PP size 1 GB is created Smilie

I have 1 more point, can you explain to me the in-band and calculation of the percentage? In the docs it says this is used to calculate the usage percentage of disk, but somehow I can see 0%, 100% but the disk has data already on it and still has free PPs.

Code:
[root@xxx] / > lslv -l fslv03
fslv03:/export/images
PV                COPIES        IN BAND       DISTRIBUTION
hdisk19           1599:000:000  20%           320:320:319:320:320
hdisk20           1599:000:000  20%           320:320:319:320:320
hdisk21           1599:000:000  20%           320:320:319:320:320
hdisk22           1599:000:000  20%           320:320:319:320:320
hdisk23           1599:000:000  20%           320:320:319:320:320
hdisk24           1599:000:000  20%           320:320:319:320:320
hdisk25           1599:000:000  20%           320:320:319:320:320
hdisk26           1599:000:000  20%           320:320:319:320:320
hdisk17           968:000:000   18%           320:178:319:151:000

[root@xxx] / > lspv -l hdisk21
hdisk21:
LV NAME               LPs     PPs     DISTRIBUTION          MOUNT POINT
fslv03                1599    1599    320..320..319..320..320 /export/images

[root@xxx] / > lspv hdisk21
PHYSICAL VOLUME:    hdisk21                  VOLUME GROUP:     vg_3
PV IDENTIFIER:      00fa6d12ed215e81 VG IDENTIFIER     00c1cc1400004c0000000128174b7c57
PV STATE:           active
STALE PARTITIONS:   0                        ALLOCATABLE:      yes
PP SIZE:            64 megabyte(s)           LOGICAL VOLUMES:  1
TOTAL PPs:          1599 (102336 megabytes)  VG DESCRIPTORS:   1
FREE PPs:           0 (0 megabytes)          HOT SPARE:        no
USED PPs:           1599 (102336 megabytes)  MAX REQUEST:      256 kilobytes
FREE DISTRIBUTION:  00..00..00..00..00
USED DISTRIBUTION:  320..320..319..320..320
MIRROR POOL:        None

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