Contributor
Contributor

Extending a VMWare Datastore in vSphere vs ESX3.5

I noticed that for vSphere there is explicit notation about dynamic growth INTO existing LUN. The support for adding extent is still there with up to 64TB however as per documentation it is said that data store can grow up to 2TB in size within the LUN. Based on the sound of this (regarding 2TB limitation which is normal, and how its worded) I am getting a sense that in vSphere the datastore growth within the same LUN as a dynamic procedure is one such as exxtending a volume in a Operating System. By that what i mean is that the entire Data Store is re-striped across the added space thus lets say you had a 10 disk raid 1/0 DiskGroup and DataStore on in and you added 4 more disks for space and extended the diskgroup, then the LUN, and then grew the DataStore, that means that the new data store would be spread across 14 disk and not have one portion spread across 10 and the extent across 4 disks (like as if you added extent from another disk group)...........is that correct? Am i interpreting that accurately because as i understand in 3.5 it would not re-stripe the DS but simple carve out new space and attach at the end of the DS. Thus anything stored there wouldn't preform nearly as good as on the original DS unless the extent was as big as the original DS and utilized 10 disks....is this accurate? can the vSphere extend the DataStore re-striping it and "SPREADING" it across added space and maintaining same preformance across the DS as long as the growth is within the same diskgroup and same LUN???

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3 Replies
Expert
Expert

I think what you are asking basically is that with ESX 3.5 you could not grow VMFS datastore dynamically which is true. You had to rebuild or add extent. With ESX 4 you can grow VMFS dynamically. However 3.5 and 4.0 both have 2TB limit on Datastore. Adding extents is bad idea as in with spanning volumes with Microsoft. If you lose volume then you lose data.

Mike

Contributor
Contributor

Yes I think you just answered my question although indirectly. I wanted to make sure that the dynamic growth operation was same as performing a rebuild in ESX3.5 and NOT as adding an extent. I never added extents or recommend doing it unless absolutely necessary so just wanted to know that the growth will actually be a restripe and wont cause any performance issues or concerns as extent would.

THanks

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Immortal
Immortal

Hello.

You understand it correctly. The dynamic expansion of VMFS volumes is a new feature for vSphere. It is discussed in What Is New in VMware vSphereTM 4: Storage There is also some good information on p.104 of the ESX Configuration Guide.

Good Luck!

Brian Atkinson | vExpert | VMTN Moderator | Author of "VCP5-DCV VMware Certified Professional-Data Center Virtualization on vSphere 5.5 Study Guide: VCP-550" | @vmroyale | http://vmroyale.com
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