Extent vs Increase Size - Not sure of the difference

[ftfcu]

I have a question about Extent vs Increase the size of a datastore.  I am not sure if they are one and the same.

If I have a 200GB LUN Presented to me and I make a 200GB Datastore.  We realize that we actually needed it to be 400GB.  In our case the SAN Administrator grows the LUN and thus we can increase the size of the datastore.  Is this an extent?  I am not adding two LUNS together to make more size.

The alternative is of course to create a NEW 400GB LUN and the storage vmotion over to it, but if the above is not dangerous or going to rob performance than we would prefer that.

Any thoughts?

[sparrowangelste · Accepted solution]

ftfcu wrote:

I have a question about Extent vs Increase the size of a datastore.  I am not sure if they are one and the same.

If I have a 200GB LUN Presented to me and I make a 200GB Datastore.  We realize that we actually needed it to be 400GB.  In our case the SAN Administrator grows the LUN and thus we can increase the size of the datastore.  Is this an extent?  I am not adding two LUNS together to make more size.

The alternative is of course to create a NEW 400GB LUN and the storage vmotion over to it, but if the above is not dangerous or going to rob performance than we would prefer that.

Any thoughts?

extent would be spanning the datastore across different luns.

increase size of datastore would actually enlarge it IF you have space avaialble on the lun or expanded it on your storage first

if the san admin grows it it isnt an extent.

svmotion to a larger datastore is fine too.

http://sparrowangelstechnology.blogspot.com/2012/07/growing-and-expanding-vmfs.html

here you can see the vm was not affected by increasing the datastore

[heitoramc]

If I have a 200GB LUN Presented to me and I make a 200GB Datastore.  We realize that we actually needed it to be 400GB.  In our case the SAN Administrator grows the LUN and thus we can increase the size of the datastore.  Is this an extent?  I am not adding two LUNS together to make more size.

No. This is a increase.

Extent: Create another LUN in SAN and then add to existing datastore. (Obs: Mixing LUNs with different speeds can affect the performance of your extended VMFS. Therefore, it is better to have all extents presented from the same storage array)

[ftfcu]

So really no need to request a larger new LUN and then migrating.  Just request the LUN be increased and then resize

[a_p_]

Yes, that's correct. The option to grow/increase a datastore was added with vSphere 4. Earlier versions required to increase the LUN/datatore size using extents. With vSphere 5 LUNs can have a maximum size of ~64TB (earlier versions only supported up to ~2TB).

André

[Gkeerthy]

one more info.... regarding the vmware extents....

i believe .. if we create the extents....the first..LUN contains the VMFS metadata... so if we grouped 4 LUNS to create a big datastore... then the entire vmfs meta data will be in the first lun so.. any thing happens to the first LUN will damage the entire datastore.. and data loss will happen..