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VMware 6.7 U2 or higher breaks MCS

Ryon Brubaker



From our Citrix tech;


"I see here that you’re being escalated due to pointers to a known issue. With MCS and versions of VMware (6.7 u2 and higher as well as VMC on AWS). I’ll be looking at your case for verification that it is truly linked to the known issue. The issue we are facing is both an inability to upload the image prep disk as well as getting caught in a change VMware made regarding the ddb.deletable flag, which was previously not being honored by VMware. We were letting the flag stay at false due to it not having an impact. It was a bug that our code was essentially “taking advantage of”. More of an oversight but not one that meaned anything as the flag had no value in vmware software at the time. Now it is being utilized (in 6.7 u2 and higher).


Both of these issues have been fixed and will be released in Citrix Virtual Apps and Desktops 1912, Citrix Cloud and will be backported in XenDesktop 7.15 CU5. CVAD 1912 is due out at the end of the year (but most likely available for public download come January 2020). In the meantime we might be able to scrounge up a private binary (or installers). But the likelihood is slim given that it’s an involved change to the product and affects a handful of services, not just a single binary like how most individual fixes can go.


Again, I’m going to try and better confirm that your case is a match by looking at your data compared to existing data on the known issue."

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Any update to this one Ryon? We are having possibly similar issues, where the dbb.deletable flag is set on a vmdk file at some point in the mcs process. We are actually using vmware 6.5 and seeing issues where the basedisks are not cleaned up due to this fact. We are still able to update catalogs, etc. But basedisks remain and are not deletable unless the flag is set to true.

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We had that issue you describe too before 6.7, but after 6.7 U2, MCS totally fails, maybe ok with updating existing catalog.  We were testing fine with 6.7, but seems 6.7 U2 and starting from scratch, it all fails.


Here is latest;


From a Citrix Escalation Engineer (Friday, 10/18/2019);

"Since we still don’t have additional workarounds in place (private for this is huge and has not been created for your version yet) and you also expressed a desire to wait until the actual release, I will proceed to archive this case for the time being. The release of CVAD 1912 will have the release. If upgrade to this version and still experience the issue, please reference this case when you reach back out. It may be too late to re-open this particular case, but we’ll keep the notes around and we know the bug we were looking for anyway.





We'll hold off until Q1, 2020.  We still run VMware 6.0 on-prem, but itching to run in CVAD w/VMC on AWS, which has 4 of these + SSD;


Hypervisor:VMware ESXi, 6.9.1, 14411217

Model:Amazon EC2 i3.metal

Processor Type:Intel(R) Xeon(R) CPU E5-2686 v4 @ 2.30GHz

Logical Processors:36

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I would, that is what we are on, since Jan, 2020.


The issue was two-fold, Citrix was lazy and used old code, VMware updated their software which then lead to the MCS feature breaking.  Long story short, get on the latest Citrix CVAD LTSR, we are able to use MCS on-prem and within "VMware Cloud on AWS" (aka VMC) without issue.

From Citrix support;

"Latest LTSR should contain the fix for VSAN 6.7’s issue of the ddb.deletable flag being set to “false” during disk creation. This fix addresses an issue with VMC and creating disks to begin with. Those two fixes turned out to be involved in the same set of files, which was why they were originally combined.


CVAD 1912 has the fix of the ddb.deletable flag issue but also the issue of VMC that was addressed in the same fix, LD2143.




Though, to be honest and safe, I have not tested this fix myself; though, I can’t really test it as we don’t have vsan 6.7 access for me to play with. But the 1912 version was tested by our development team and confirmed that the fixes listed are still valid. Of course in a customer environment, things can happen differently. Please let me know when you’ll be able to test."


Good luck!

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