if we Unmount a datastore what does it mean

[MrVmware9423]

Dear Team,

Quickly wants to check , if I Unmount one of the datastore what does it do in the background and what It means (is it means that now this datastore is safe to delete, no I/O operation will be performed), if We Unmount a datastore will I loose any data???

regards

Mr Vmware

[Alim786]

Hi Mr Vmware

If you unmount a Datastore from an ESXi Host, then the files are now inaccessible by that Host. It is normally a pre-cursor to removing/unpresenting that LUN from the ESXi Host from within your Storage Admin Console. You have to beware of certain pre-requisites before you do this. The article link below gives you more information :-

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2004605

All the best !

[MrVmware9423]

Thanks Alim,

what is the difference between unmount and detach??? need ur assistance on the same.

[Vivek Singh]

Hi Mr,

Unmount - It unmounts the VMFS filesystem from the ESXi host.

"When you unmount a datastore, it remains intact, but can no longer be seen from the hosts that you specify. The datastore continues to appear on other hosts, where it remains mounted"

Detach   -  It will disconnect the host connectivity with the Storage system. Though the LUN is still visible on ESXi host until removed from the Storage side.

It is same like ejecting the device. Example, when you do the USB device eject. You click on the small Icon and "Eject my USB" . Though the USB is still connected until you pull it out.

Thanks,

[Alim786]

Unmount removes the "Datastore" from the Host.

Detach removes the "Device" or as I like to think the "Path" to the Datastore.

This was originally brought in to prevent a possible APD(All Paths Down) Loss scenario. Cormac Hogan has a great blog on it here :-

detach | VMware vSphere Blog - VMware Blogs

All the Best !

[Punitsolanki]

Unmount is just going to detach the device from that host and you do not loose any data,

Delete option will delete the data from your datastore.

[MrVmware9423]

to safely remove a datastore from one esxi host without loosing data and need to map same datastore on other esxi host for that I have to deatch a datatore from 1st esxi and map the same on second ESXi. Please correct me if I am wrong.

[Alim786]

Yes you are correct. Remember you unmount and detach from VMware and then unpresent the LUN from your Storage Admin Console. You then present the LUN to the new ESXi Host from your Storage Admin Console and then Rescan storage from that Host in VMware.

I hope this is clear.

[MrVmware9423]

Thanks Alim,

once I mapped the same datastore on another esxi host , so it will contain all data  can register a VM  from same datastore without no issue.

[Alim786]

Please see my link to the KB article above. You must either move the VMs to another Datastore or Unregister the VMs from the Host that the Datastore is mounted to BEFORE unmounting.