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Ramifications of not using MCSIO


Cathy Leik

Question

We are having a lot of problems with the MCS write cache filling up on our non persistent Win10 desktop catalogs despite disabling everything known to man kind regarding updates.  This is with CVAD 1909.  With 7.15cu4 we had no issues.  

 

What are the ramifications of not using MCSIO?  The writes will go to C: and be lost on reboot, the pagefile will stay on C: and obviously we can't redirect event logs to the write cache drive but other than all of that is there an issue with doing it this way?  We have a lot of space on the C: drive and we wouldn't have to worry about this silly issue.

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7 answers to this question

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I gave up with MCSIO on Win10 a while back.   I had persistent problems with machine crashes, blue screens, machines freezing and needing a hard reboot etc.   A catalog of 50 machines might have 4 or 5 failures a day.   So, I created a new machine catalog with the MCSIO feature turned off, but using the same master image, and everything suddenly became a lot more stable and with no obvious performance penalty.

 

We do have fairly fast hardware though.   The penalty might be more noticeable if we weren't running on hyperconverged with all the storage effectively being all local SSD.

 

But to answer the question - it's fine to do that, worst case is it's a little slower.   '**** it and see', as they say.

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MCSIO in the new world is great - forget anything you know about the old release - that was fundamentally broken and was pulled by Citrix - if you didn't have issues, you are very lucky

 

never upgrade an image and then switch to the new MCSIO engine if you were using the old, uninstall the VDA, reboot, cleanup utility, then reinstall the new agent with the new engine and go from there

 

you don't have to use MCSIO, but if you have storage bottlenecks, it's worth its weight in gold

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James, what is classed as 'the new world' in this case?   I started with 7.15 but maybe the newer ones are better?

 

I'm quite happy to give it another go but nervous about doing so.   Some of my catalogs have hundreds of machines so even a small percentage increase in machine failures makes a big difference to ticket volumes and user irritation.   On the other hand, with all our hardware being VXRail, the CPU drain from running the integral vSAN is quite significant, so reducing demand from the storage systems would be helpful across the whole environment.

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It was one of the 19x releases that introduced the rewrite of mcsio - ground up change so everything in the old 7.15 style release is dead and gone (hooruh)

 

results so far are pretty good, you are best to test in your environment on a dedicated catalog but for the most part it’s been like PVS performance which is really good 

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Performance wise I can vouch for version 1909 that we are on.   Our problem is more about Windows 10 and the services that start other services and trying to track down all the disk writes going on in the environment.   Although at the moment after rolling out a centralized Windows Defender update share we are stable.

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I have seen, in Nutanix environments, where they do not use MCSIO at all (presumably because locally-attached Temp Disk Cache - SSD's - is already so fast?) ... Also, in our environment, our VDAs all live on an All-Flash Storage system, which is very fast, so I'm wondering if we even NEED MCSIO (the current v2 version)?  We too are having the issue with machines crashing all the time and I have a very strong inclination to get RID of MCSIO all together...

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