September 1, 2014

Maximum LUN resize limits on NetApp

One thing to be aware of is there are limits to resizing a LUN, I’ve seen customers that will create a very small LUN thinking they can just grow that as big as they need to in the future. Due to the geometry of the LUN at the time it was created it can only be resized to a maximum of ~10 times the original size of the LUN.

One way to see this is at the command line, for the command to be available you need to run ‘priv set diag‘ and then you will have access to the ‘lun geometry‘ command. From there you can see the LUN size as well as the maximum LUN size that is available.

Here is a 10g LUN and I can see my maximum size available is 502gb, not exactly 10x but the reason for that is the lun geometry doesn’t change until you hit 50gb, so anything up to that point can be extended 10x the 50gb size.

Once I create a LUN of 51gb or larger the values for the SCSI geometry change and now my max resize is 1004gb, the 1004gb maximum is for lun sizes between 51g and 100g.

As you can see, the next change will come at a 101gb LUN, 101 to 150gb max resize is 1506gb

Here is a table of some of the results:

LUN Size Maximum Resize
< 50g 502g
51-100g 1004g
101-150g 1506g
151-200g 2008g
201-251g 2510g
252-301g 3012g
302-351g 3514g
352-401g 4016g

etc..

About mike
I am currently a Cloud Technical Solutions Architect working for World Wide Technology in the Twin Cities, MN area. My professional summary is available via my LinkedIn page. I can be contacted by the Contact Me link at the top of the site. I also spend (too much) time on Twitter so feel free to follow or send me a tweet.