Snapshots that are created by SMHV

[#1]

I have been noticing some funny things and wanted to know if there was an explanation for what they mean.

I look at two snapshots of the same volume:

  1% ( 1%)    1% ( 1%)  Mar 16 01:11  VIRTUAL_03-16-2010_01.00.41_backup (busy,LUNs)
  1% ( 0%)    1% ( 0%)  Mar 16 01:09  VIRTUAL_03-16-2010_01.00.41 (busy,LUNs)
  6% ( 5%)    3% ( 2%)  Mar 15 01:14  VIRTUAL_03-15-2010_01.00.00_backup
  6% ( 0%)    3% ( 0%)  Mar 15 01:10  VIRTUAL_03-15-2010_01.00.00

1. What does " (busy,LUNs)" mean?
2. Why does SMHV always create a snapshot and a snapshot_backup? What do each of them mean?

Next, I was looking to mount a snapshot of one of my VM LUNs and I see:

• VIRTUAL_03-15-2010_01.00.00_backup
  • Q_ VIRTUAL_03-15-2010_01.00.00_backup
    • Virtual.LUN
      • Virtual.LUN_Exclude

What does the _exclude mean?

Thanks,

Reuv

[#2]

Hi,

The two snapshots are created in response to "auto-recovery" done by Hyper-V VSS writer during VM backup.

Hyper-V writer creates a software of snapshot of all the VHDs inside the VM (using system provider). This is captured in the first snapshot on the storage system. The applications and OS in the VM is not frozen when the snapshot is created on storage system. So, later, VSS asks us to mount the first snapshot and the writer then does auto-recovery to revert the hardware snapshot to the software snapshot taken earlier. When auto-recovery is complete we take the second snapshot (_backup suffix).

Hence, the second snapshot should always be used for "connect" operations. The different between the two snapshots is essentially the auto-recovery changes.

I also wanted to check if you are running an evaluation copy of SMHV? The released version is available on NOW.

Regards

Amrita

[#3 · Accepted solution]

About the '_exclude' LUN.

During Autorecovery VSS asks VSS hardware provider to mount the first snapshot(backing).

Snapshot mount is done with a LUN clone created in the active file system. During the mount the original LUN is renamed as lun-name_exclude and the LUN clone is renamed as LUN.

The VSS writer then does auto-recovery to revert the hardware snapshot to the software snapshot taken earlier.
When auo-recovery is complete we take the second snapshot (_backup suffix). After the second snap is complete, LUN is renamed back to the original name.

So in short _exclude is the original LUN in first snapshot. The autorecovery phase renames the original lun to "Lun-name_exclude" so that it will be excluded

for the ndmp dump utility. The clone created for autorecovery will have the name of the original lun.

Following link has more details about the changes required to support the NDMP dump.
http://wikid.netapp.com/w/SnapDrive_for_Windows/VSS/VSS_Autorecovery_ERRD#Standard_NDMP_Dump

Thanks,

Vineeth

[#4]

( Both of your answers were correct and helpful - any way I can mark both as correct? )

I cannot access the DNS name for wikid.netapp.com. Is that an intranet site? Can you pdf/link me the content in another manner?

Reuv

[#5]

Hi

I don't think you can access that wiki page. I am sending you a mail with the detailed steps.

REgards

Amrita

[#6]

I did notice however that unlike the _backup, the _exclude did NOT show up on all of my snapshot copies of my LUNs. Is there a reason why it appears sometimes and not others?

[#7]

_exclude only shows up in auto-recovered snapshot copies of the LUN (the one with _backup suffix).

[#8]

I see that. What is the funny string. RWS file that we see - which I also see on my live LUN? Is that like a working copy of my LUN?

[#9]

.rws file is the file which contains the LUN clone.

Thanks,

Vineeth

[#10]

Hi,

What are the consequences on QSM and Snapvault ?

I don't know if I'm wrong but with my test QSM/SV consider that there is a new LUN to transfer ?

Thanks.

Valery.