Hyper-V Differencing Disks - how to merge multiple levels of differencing disks
Hello:
I inherited an SBS 2011 system which is setup with Server 2008 R2 as a host server running Hyper-V; the SBS2011 system is installed as a VM with a single "drive" that is partitioned in Windows into C:\ and D:\ partitions. And performance is terrible. I think the following setup choices are major causes of the performance issues.
The virtual disk on which SBS2011 is installed has two levels of differencing disks; that is, there is a dynamically-expanding VHD file, then a differencing disk that says the VHD file is its parent file, then a second differencing disk that says the first differencing disk is its parent disk.
In Hyper-V Manager, the "media" that the SBS2011 VM identifies as its hard disk is the second differencing disk; if I click the "Inspect" button, the second differencing disk's specs are given and it identifies the first differencing disk as its parent. If I then click the "Inspect" button in this window, the specs for the first differencing disk are given and the actual VHD is identified as the first differencing disk's parent.
So, the hierarchy appears intact and the system runs. However, the SBS 2011 VM runs Exchange and SQL, so I think the use of differencing disks, plus having the VHD file setup as dynamically-expanding, cause the performance issues.
My questions are:
1. This setup is just not a good idea for an SBS2011 VM, right?
2.a. Assuming no, what is the best way to merge everything back to the parent disk (no other VMs use the VHD file)? I found this article ("https://technet.microsoft.com/en-us/library/ee941134(v=ws.10).aspx") but it does not cover having two levels of differencing disks so I was unsure of how to proceed.
2.b. Also, how much free drive space on the host server will be needed to do the merge? Do I need at least 2x of free space compared to the amount of space used by the VHD, differencing disk 1, and/or differencing disk 2? If so, this is a problem as there is not enough free space. As such, can I power off the VM, merge the files to an external drive, move the merged VHD file back onto the primary drives, and finally start the VM after telling it to use the merged VHD file as the media for its disk?
3. If and when the differencing disks are merged, converting the VHD to a fixed size should help performance, right?
Thanks!
Mike
I inherited an SBS 2011 system which is setup with Server 2008 R2 as a host server running Hyper-V; the SBS2011 system is installed as a VM with a single "drive" that is partitioned in Windows into C:\ and D:\ partitions. And performance is terrible. I think the following setup choices are major causes of the performance issues.
The virtual disk on which SBS2011 is installed has two levels of differencing disks; that is, there is a dynamically-expanding VHD file, then a differencing disk that says the VHD file is its parent file, then a second differencing disk that says the first differencing disk is its parent disk.
In Hyper-V Manager, the "media" that the SBS2011 VM identifies as its hard disk is the second differencing disk; if I click the "Inspect" button, the second differencing disk's specs are given and it identifies the first differencing disk as its parent. If I then click the "Inspect" button in this window, the specs for the first differencing disk are given and the actual VHD is identified as the first differencing disk's parent.
So, the hierarchy appears intact and the system runs. However, the SBS 2011 VM runs Exchange and SQL, so I think the use of differencing disks, plus having the VHD file setup as dynamically-expanding, cause the performance issues.
My questions are:
1. This setup is just not a good idea for an SBS2011 VM, right?
2.a. Assuming no, what is the best way to merge everything back to the parent disk (no other VMs use the VHD file)? I found this article ("https://technet.microsoft.com/en-us/library/ee941134(v=ws.10).aspx") but it does not cover having two levels of differencing disks so I was unsure of how to proceed.
2.b. Also, how much free drive space on the host server will be needed to do the merge? Do I need at least 2x of free space compared to the amount of space used by the VHD, differencing disk 1, and/or differencing disk 2? If so, this is a problem as there is not enough free space. As such, can I power off the VM, merge the files to an external drive, move the merged VHD file back onto the primary drives, and finally start the VM after telling it to use the merged VHD file as the media for its disk?
3. If and when the differencing disks are merged, converting the VHD to a fixed size should help performance, right?
Thanks!
Mike
ASKER CERTIFIED SOLUTION
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
ASKER
Thanks!
ASKER
Hi:
Here is where I found the instructions on adjusting the RAM cache limits for Exchange 2010:
http://www.bursky.net/index.php/2012/05/limit-exchange-2010-memory-use/
Here is where I found the instructions on adjusting the RAM cache limits for Exchange 2010:
http://www.bursky.net/index.php/2012/05/limit-exchange-2010-memory-use/
This is a very bad setup if you ask me. SBS is designed to run on physical boxes in that way it can utilize all possible resources from it. Exchange has a tendancy to utilize 90% of all available memory but SQL has almost the same behaviour so why are they running on the same machine? (Very bad)
You suspect hdd performance is slowing down performance, i wonder why. Do you see very high utilisation in hardware monitor? I would suspect it is suffering from memory availabillity.
Please check which resources have very high counters in usage.
Cheers