lslv Mirroring Question 2

[ralisp]

I have two HD's hdisk0 / hdisk1 mirrored in rootvg. The result of 'lslv -l lv12' is:

lv12:/home/socats
PV COPIES IN BAND DISTRIBUTION
hdisk1 200:000:000 34% 052:069:079:000:000
hdisk0 200:000:000 33% 056:066:078:000:000

First, shouldn't both be 100% IN BAND? And second, if not both 100% IN BAND, should they add up to 100%?

If they both added up to 100%, I'd migratelv from one disk to the other and then mklvcopy back to the other disk to mirror. My concern is something is wrong and performing the migration would corrupt the lv. I haven't had any issues with the data in the LV/FS. The server has been up for over 500 days. I'm running AIX 4.3.3
Any suggestions would be appreciated!

 

[RodKnowlton]

IN BAND" refers to what percentage of physical partitions follow the INTRA policy (look at "lslv lv12") for placement on the disk.

Your lv12 is set to "outer middle", and the 69 and 66 partitions allocated there account are 34% and 33% of the 200 partition size.

Unless you care about the physical location of each lv on physical disk platters, which in most cases* few do, you've got nothing to worry about here.

*if mirror write consistency is on, high traffic disks can benefit from being on the outer portion, as the MWC info is written on the edge**.

**unless I got that backwards (again), in which case I'm sure someone will chime in.

Rod Knowlton

IBM Certified Advanced Technical Expert pSeries and AIX 5L
CompTIA Linux+
CompTIA Security+

 

[ralisp]

Thank you Rod. I guess I should be concerned if the # of copies don't match. In this case they do, so I should be fine.
-Your quick response is greatly appreciated!

 

[RodKnowlton]

ralisp,

The copies won't necessarily always be equal. What you have is the simplest of scenarios, a logical volume fully contained on a single drive, then mirrored with the mirror copies all going to another single drive. The Logical Volume Manager is capable of handling much more complicated arrangements, including keeping more than one copy of a logical partition on the same drive (silly as that may be).

Check "man lslv" for more info on what the Copies field represents.

Rod Knowlton

IBM Certified Advanced Technical Expert pSeries and AIX 5L
CompTIA Linux+
CompTIA Security+

 

[p5wizard]

If you want to be sure that everything is ok re mirroring, look at lsvg -l <yourvg>

For two-way mirrors, you need PP column double of LP column
and open/syncd or closed/syncd in State column.

Of course, that doesn't give you any clues as to where exactly the mirrors are... Use lslv -m <yourlv> for that.



HTH,

p5wizard