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Full Discussion: How to know exactly which physical partion contains data?
Operating Systems AIX How to know exactly which physical partion contains data? Post 302928585 by bobochacha29 on Saturday 13th of December 2014 01:08:12 AM
Old 12-13-2014
Quote:
Originally Posted by rbatte1
Are you wanting to shrink the filesystem, replace a disk or something? I'm wondering why you are so interested.

To shrink a filesystem on AIX is not simple task like it can by on some other operating systems, for instance RHEL 6 has an option to re-size up or down the filesystem and logical volume all in one command, although it requires it to unmount as part of the process.

On AIX you would need to either:-
  1. Build a new filesystem of the required size, move the data and then remount the new filesystem to the correct location (making the change permanent for next boot etc.)
  2. Backup the data, destroy and re-create the filesystem and then restore the data.
If you are looking to free up or replace a disk, then migratepv is your friend here. It can take a while depending how big your filesystem is, but it will (one at a time) make a copies the LPs to the target drive then remove the old one. Do not interrupt the process as this can leave you with inconsistencies in the volume group and logical volume information.
Code:
migratepv -l logical_volume  source_disk  target_disk

An alternate would be to use mirrors to achieve this if placement is critical. You can use mklvcopy to add a third copy to the new disk (and synchronise them) and then use rmlvcopy specifying to remove the one from the old disk. When making the 3rd copy, you can specify a map-file to force it to use the PPs on whichever disk in whichever order you want if that is important.

Whichever technique you use, you can empty a disk and remove it from the volume group for replacement or use elsewhere.


If I've missed the point, then let us know what you really need to know and we will try to help.



Regards,
Robin
Hehe, how do you know that. It's true that I'm having problem with filesystem, but it's a little different with what you think. In fact, I want to split the data of a filesystem on multiple hard disks equally.
It's quite a waste of lines listing all the lp/pp of the real filesystem I'm handling, so allow me to use that /movelv_test as an example.

This is how it looks like
Code:
fslv01:/movelv_test
LP    PP1  PV1               PP2  PV2             
0001  0175 hdisk1            0111 hdisk2            
0002  0176 hdisk1            0112 hdisk2           
0003  0177 hdisk1            0113 hdisk2            
0004  0178 hdisk1            0114 hdisk2           
0005  0179 hdisk1            0115 hdisk2            
0006  0180 hdisk1            0116 hdisk2            
0007  0181 hdisk1            0117 hdisk2           
0008  0182 hdisk1            0118 hdisk2           
0009  0183 hdisk1            0119 hdisk2           
0010  0184 hdisk1            0120 hdisk2          
0011  0185 hdisk3            0121 hdisk4          
0012  0186 hdisk3            0122 hdisk4            
0013  0187 hdisk3            0123 hdisk4           
0014  0188 hdisk3            0124 hdisk4           
0015  0189 hdisk3            0125 hdisk4           
0016  0190 hdisk3            0126 hdisk4            
0017  0191 hdisk3            0127 hdisk4            
0018  0192 hdisk3            0128 hdisk4            
0019  0193 hdisk3            0129 hdisk4           
0020  0194 hdisk3            0130 hdisk4

( Don't be surpised why it looks like that. At first, the vg of this fs have only 2 pv, hdisk1 and hdisk2. The data grew up day by day and when there was no free pp on hdisk1 and hdisk2, we added two more pv: hdisk3 and hdisk4 to the vg and then increase the /movelv_test size . Now this fs 's Used% is ~ 55%, 180GB assigned to the fs/ 100GB data used )

The problem is when I checked the disk operation ( by command "topas" ), I found that the operation of hdisk1 and hdisk2 is very high, ~90%-100% while the operation of hdisk3 and hdisk4 is just ~ 10% ( most of the disk operation is writing - the application writes logs to the fs's mountpoint ).

The result of the "topas" command and the lp/pp listed above made me think that data fills the raw disk space like water fills a bucket - as bakunin said, but now I know it's not true.

Now, what I want to do is to balance the disk operation of these 4 pv ( just only at this time,temporarily don't care about data increasing ) and I intend to do like this:
_ Decrease the size of the fs so that the fs's Used% ~ 99% ( to ensure that most of the pp are filled with data and don't care whether the pp contains data or not ), in this case - decrease size of /movelv_test to 101 GB
_ Used "migratelp" command to arrange each pp of the fslv01 like this
Code:
fslv01:/movelv_test
LP    PP1  PV1               PP2  PV2             
0001  0175 hdisk1            0111 hdisk2            
0002  0176 hdisk1            0112 hdisk2            
0003  0177 hdisk1            0113 hdisk2            
0004  0178 hdisk1            0114 hdisk2            
0005  0179 hdisk1            0115 hdisk2            
0006  0180 hdisk2            0116 hdisk3            
0007  0181 hdisk2            0117 hdisk3            
0008  0182 hdisk2            0118 hdisk3            
0009  0183 hdisk2            0119 hdisk3           
0010  0184 hdisk2            0120 hdisk3            
0011  0185 hdisk3            0121 hdisk4            
0012  0186 hdisk3            0122 hdisk4            
0013  0187 hdisk3            0123 hdisk4            
0014  0188 hdisk3            0124 hdisk4            
0015  0189 hdisk3            0125 hdisk4            
0016  0190 hdisk4            0126 hdisk1            
0017  0191 hdisk4            0127 hdisk1            
0018  0192 hdisk4            0128 hdisk1            
0019  0193 hdisk4            0129 hdisk1            
0020  0194 hdisk4            0130 hdisk1

_ Increase the size of the fs back ( in this case is 180 GB )

And I have two questions
1. Is it OK to use the command " migratelp" to do something like this. The data availability, the synchronization between the 1st mirror and the 2nd mirror ... is OK ? Are there any errors of the filesystem, errors of data, ... after using this command? If 1 of 4 hard disk fails, the data is still OK ???
2. Does this solution work ? Are there any solutions better?

Sorry for my poor English. Thanks for read.
 

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