Comments on: Proper Use of Hyper-V Dynamic Disks

By: Jun

Jun — Wed, 27 Mar 2019 06:33:00 +0000

I think that, as Eric says, on the first FUD – I do see the psychology against the dynamically expanding disks. It’s sorta like advocating to spend from checking account, monitoring your balances versus living on credit card, monitoring the sum of your credit limits. There’s something inherently yucky about the latter.

So. If you can be disciplined, credit cards are awesome. If you can’t, it’s a hell.

Technology wise, especially in 2019, I have absolutely nothing against dynamically expanding – and I am a SQL guy, nuts about that last 0.5 percent of performance. I’m here just explaining the psychology of it.

By: Marty

Marty — Thu, 21 Jan 2016 16:52:00 +0000

Because of the overwhelming bias and opinion spread as fact by “IT Professionals”, i have been getting crap for years for using Dynamic disks. You said it best “Because end-users cannot detect a 1-2% performance difference..”.
All environments are different, but in most cases, that 1-2% difference in performance won’t make a bit of difference. If your environment needs that extra performance, like the OP said, virtualization is not for you.

By: Stig Martinsen

Stig Martinsen — Wed, 30 Dec 2015 20:04:00 +0000

Great article! I almost exclusively use dynamically expanding vhds because of all the benefits you describe here. Thanks!

By: Rick

Rick — Mon, 06 Oct 2014 15:50:00 +0000

Great article. We are getting so tired of hearing so-called experts and vendors that we have to convert to fixed VHDX’s (VHD). And some are bold enough to state that they will not support you because of use of dynamic VHDX’s (a competitor backup vendor). We have always used dynamic for over 6 years except on a few VM’s (mixed as the OS disk is always dynamic) and never have had issues. It is refreshing to see an article to call out the FUD.

By: Ed

Ed — Thu, 20 Feb 2014 18:09:00 +0000

I’ve been using dynamic expanding disks for exchange and sql for over 2 years without any issues. I just start reading more about the differences and deciding if I should convert it to fixed disk on my 2012 servers. I’m not sure how much improvement in performance I’ll get by converting.

By: Jay Liang

Jay Liang — Fri, 09 Aug 2013 20:35:00 +0000

Thanks again Eric.

By: Eric Siron

Eric Siron — Thu, 08 Aug 2013 21:14:00 +0000

In reply to Raymond. The dynamic disk volume type is never recommended in physical or virtual machines unless you have a definite use for it. As in, you're going to install Microsoft Data Protection Manager.

By: Raymond

Raymond — Thu, 08 Aug 2013 21:10:00 +0000

Hi, so the dynamic disk is not recommended in virtualization ? (i mean the dynamic logical disk in virtual machine)

By: Eric Siron

Eric Siron — Thu, 08 Aug 2013 12:36:00 +0000

In reply to Jay Liang. No, there is no special concern for using dynamic VHD with Active Directory. The only reports of corruption I've seen had to do with the new VHDX format and incorrect disabling of the system file cache. These problems should have been corrected in patches.

By: Jay Liang

Jay Liang — Wed, 07 Aug 2013 23:31:00 +0000

I have been keep on trying to read more and more articles and arguments about the “Proper Use of Hyper-V Dynamic Disks” for many years. And I did end up go with similar practices of production use you mentioned with Dynamic VHD ( or the mix&match of other type of VHD within one VM) starting Hyper-V 2.0. It is great knowing also recommended (or green light) for Server OS in production use too. I do agree mostly on this, however, would there be any concerns for server with AD role? Another question is VHD corruption (I haven’t seen one yet), wonder if any studies/real cases regarding the corruption rate on Fixed vs Dynamic? People reading this forum pretty much know the Pro and Cons between Dynamic vs Fixed, as Eric mentioned, the focus here is to provide a better understanding of Dynamic VHD and how to properly use them for your needs. In fact, as IT, we all are interesting in knowing how to safely and efficiently make use of Dynamic VHD the best we can. And we should also agree that storage planning mistake is no a Con for using Dynamic VHD.
This post is helpful for me.
Thanks Eric.