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MCS Full Clone vs Fast Clone Base Disk IOP testing


Kent Bratt1709154576

Question

I have been doing extensive disk speed testing on my existing VDIs and wanted to know if this is expected from what others know or have seen or if it even matters as the IOPS are more than a single VDI would typically need. 

XenDesktop 1903 - VDA 1903

 

What I have found is that when testing the IOPS on my MCS - Linked Clone - Windows 10 - Dedicated Virtual desktop catalog, my disk speed results are very poor and it appears to be caused by the Fast Clone / Linked Clone. If I create a new catalog from the same Image on the same storage using full clones, the disk performance tests are 20x better.

 

If I attach a 2nd Drive (D:) to the Fast Clone VDI from the same backend storage as the C: Drive, my speed tests are 20x faster on that Drive. 

Testing on the C: Drive pins the CPU at 100%, but testing on the D: Drive leaves the CPU around 60%. 

 

If I do the test on the Full Clone, the C: Drive performs great and the CPU stays around 60% during the tests. 

I've validated this with multiple different storage subsystems and get the same result, spinning disk and All Flash etc. 

 

Is this a known expectation? 

I don't think this is the same issue in this forum, but maybe related. I am not using MCSIO here as they are Dedicated machines. 

https://discussions.citrix.com/topic/395312-xd-mcs-io-is-crazy-slow/?page=3

 

For Example here are some results, IOMeter had similar results. 

 

Diskspd.exe - 20% read - 80% write - 4K block  - 10GB test file - Random I/O - 8 outstanding operations - 30 second run time

 

Linked Clone : 

Total IOPS: 1,232

Read IOPS: 244

Write IOPS: 987

 

Full Clone: 

Total IOPS: 27,156

Read IOPS: 5,426

Write IOPS: 21,730

 

Thanks, 

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It is bit surprising to see this dramatic difference.  From OS point of view, it does not know if it is on thin-clone or full-clone.  I think it is underline storage/hypervisor function that makes difference.  What hypervisor and storage solution you are using?  

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