VSS_WS_FAILED_AT_PREPARE_SNAPSHOT on SMB

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Re: VSS_WS_FAILED_AT_PREPARE_SNAPSHOT on SMB

Veeam Logoby Rumple » Thu Feb 15, 2018 2:24 am

The Level 2 resource is from Veeam that I am waiting to hear from.

I could always do a diskshadow vss backup from the hyperv servers (once I knew the command lines to use)

Veeam backups only work if I run them crash consistent but if they call VSS it always fails. Doesn't make much sense as Veeam should basically be doing the same thing as the command line (using API's I assume).
Rumple
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Re: VSS_WS_FAILED_AT_PREPARE_SNAPSHOT on SMB

Veeam Logoby Rumple » Tue Mar 13, 2018 9:42 pm

Wanted to provide an update on this issue. It appears we've hit a netapp bug that's getting fixed soon (thankfully I am on 9.1P7 at moment and not 9.2) so after the 24th I should be able to confirm if the issue is resolved. Its been a long painful road to get to this point but we are hopefully at the end of this road.

Hi Mark,

As discussed over phone last week, looks like you are hitting bug 1134071. Unfortunately there is no work around suggested for it as of now, however, it states that – “The Windows application that is trying to perform the byte lock downgrades can work around this issue by changing its locking sequence to release the exclusive byte lock first before establishing the shared byte lock for the file offset range”.

One other way to get around this would be upgrading to 9.1 p12. I am listing the public report for the bug below for your reference.

https://mysupport.netapp.com/NOW/cgi-bi ... ay=1134071
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Re: VSS_WS_FAILED_AT_PREPARE_SNAPSHOT on SMB

Veeam Logoby Mike Resseler » Wed Mar 14, 2018 7:50 am

Mark,

Many thanks for letting us know. Unfortunately I cannot go to the link (I don't have a username/ pwd for Netapp but colleagues have so I will ask them :-)). So 10 more days and it should get fixed, did I get that correct?
Keep us informed
Mike Resseler
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Re: VSS_WS_FAILED_AT_PREPARE_SNAPSHOT on SMB

Veeam Logoby Rumple » Wed Mar 14, 2018 2:38 pm

oops..forgot that was paywalled :)
They say its going to be fixed in the MArch 23rd release of 9.1 and may release of 9.2 so we will soon see...

herei s bug details.

Bug ID
1134071
Title SMB byte lock downgrades do not work on ONTAP
Duplicate of
Bug Severity 2 - System barely usable
Bug Status
Product Data ONTAP
Bug Type Unknown
Description
Formatted An issue in ONTAP causes Server Message Block (SMB) byte lock downgrades
to work incorrectly on ONTAP. When an SMB client establishes an exclusive
byte lock on a file offset range, and then subsequently wants to downgrade
the byte lock to a shared byte lock on the same file offset range -- while at
the same time does not want any other SMB client to acquire an exclusive byte
lock on the same file offset range -- the following occurs:
1. The SMB client will acquire a shared byte lock on the same file offset range
and this will be granted without any waiting period since the SMB client
already has an exclusive byte lock.
2. The SMB client will release the byte lock for that file offset
range. At this point the SMB server should release the exclusive byte lock.
Instead ONTAP misbehaves by releasing the shared byte lock that was established
on that file offset range.
3. While the application assumes that the file is left with a shared byte lock,
ONTAP has left an exclusive byte lock on that file offset range. This causes
other applications wanting to establish the shared byte lock to indefinitely
wait until the byte lock is released by the first application.


Workaround
Formatted There are no workarounds available within the ONTAP software. The Windows
application that is trying to perform the byte lock downgrades can work around
this issue by changing its locking sequence to release the exclusive byte lock
first before establishing the shared byte lock for the file offset range.


Notes
Formatted This issue has been seen with customers using SnapManager for Hyper-V to create a
VSS snapshot for VHDX files stored on SMB shares.

Note that the locking and unlocking offset ranges for the exclusive and the
shared byte lock sequences need not be exact matching ranges. They can be
overlapping each other and experience the same issue.
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Re: VSS_WS_FAILED_AT_PREPARE_SNAPSHOT on SMB

Veeam Logoby Mike Resseler » Fri Mar 16, 2018 6:58 am

No worries. Thanks for the copy/paste. Keep us informed if the patch in a few weeks solves the issue
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Re: VSS_WS_FAILED_AT_PREPARE_SNAPSHOT on SMB

Veeam Logoby Rumple » Thu Apr 12, 2018 7:44 pm

As a follow up to this, we installed the latest 9.1 p12 from NetApp and voila, VMs on SMB magically backup successfully now
Apparently this fix is coming soon to 9.2 and 9.3 NetApp versions as well
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Re: VSS_WS_FAILED_AT_PREPARE_SNAPSHOT on SMB

Veeam Logoby Mike Resseler » Fri Apr 13, 2018 5:29 am

Thanks Mark!

Really appreciated. If you happen to hear when that fix is available for 9.2 and .3 also, it would be greatly appreciated if you tell us!

Mike
Mike Resseler
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