Converting VHDs from Dynamic to Static. Time?

[Gongalong]

Hi folks,

 

We have a dynamic VHD that's currently around 1TB. I want to convert that to a static VHD of around 1.2TB.

 

Anyone know very approximately how long that will take? e.g. hours or days

 

TIA

[deano]

It really depends on where the VHD is stored. I find that our San (attached via iSCSI) is fine for disks upto 100gb, but after that it's hopeless.

 

If I need to mess with anything bigger than 100gb, then I copy it locally. Make sure it's not on a raid setup either as this can slow the process down as well, unless it's raid 0/1 or 10.

 

What tool are you intending to use as well? I find vhdtool from sysinternals is very quick. I extended my 500 to 1tb and left it going over night

[Gongalong]

This is a Hyper-V VHD, in case it makes any difference.

 

I was going to use Hyper-V (there's a guide here How to convert Hyper-V dynamic disk to fixed disk ) but our thirdline consultant has said that Hyper-V creates a new file rather than updating the original file (!). Is that definitely the case?

 

The problem is that we don't have a lot of space on our SAN, and that's RAID6 as well (based on your mention of speed issues with SANs above).

 

If the worst comes to the worst we can stream it off onto an external hard disk and convert there, if necessary. Although I don't know how I'm going to access that with Hyper-V...

[Gongalong]

To confirm it is definitely the case with Hyper-V at least. I powered down a non-essential VM and tried to convert the disk... it's creating a whole new VHD.

 

The difficulty now is converting two VHDs which are both over 1TB. We don't have space on the SAN, so presumably we'll need to attach a USB HDD to the Hypervisors.

[Gongalong]

I tested the conversion of a 25GB Windows 2008 R2 server to a fixed (40GB) VHD, and it took 10 minutes.

 

The Hypervisor it was being converted on has 16 core opterons with 72GB of RAM (also 2008 R2).

 

The SAN is an HP MSA2312i.

 

If I do more conversions I'll try to remember to put the benchmarks here. 1TB will be interesting...

[deano]

definitely try to do it local somewhere that has enough storage if you can

[Gongalong]

It looks very much like it will have to be a USB HDD attached to the Hypervisor, as it will need to be something that Hyper-V can see.

[Gongalong]

To update: I converted a 1.2TB dynamic VHD to a similar sized fixed VHDX and it took around 12 hours. This was on a USB2 drive attached to the node. Similar really to the copy speed to the drive, around 20-30MB/s.

 

Currently I'm converting a 2TB dynamic VHD, again to a fixed VHDX. It seems to be taking a similar time, but I'm having to convert from the SAN to the USB2 drive (not enough space to convert it on the drive).