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My brother is using a hosting provider which is providing his company with a VM with Windows Server 2008 R2.

They unfortunately have to run the whole stack on one server, so my brother at least asked for separate drives for OS, IIS, DB, Logs, etc.

They provided him with 5 logical drives all on the same "physical" disk 0 (e.g. showing to the OS as a physical disk -- one VMDK).

Assuming that there's a reasonable churn across these various logical disks, would adding them as separate "physical" disks (VMDKs I suppose) make sense? It seems like there would still be a performance gain there but I'm unsure how best to go about proving it and haven't found any literature (yet) on the subject.

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would adding them as separate "physical" disks (VMDKs I suppose) make sense?

Yes, you don't have to prove it, it's common sense, it just costs money is all. Of course that 'single physical disk' could well be a VMDK on a datastore based on a LUN that's wide-striped across hundreds of disks - the only way to know is to ask EXACTLY what they're providing and EXACTLY how - then you'll be able to make an informed decision.

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  • Thanks for responding! I'm interested in the language to explain it. The issue is my brother's host is telling him they won't put it on separate disks because it "makes no difference in a VM". So I guess I'm wondering, would using separate VMDKs always guarantee some better performance, or no? Oct 6, 2015 at 11:25
  • Taken at face value their assumption that 'makes no difference in a VM' is utter shit but this could well be a terminology issue - which is why I'd suggest you get them to spell it out in great detail - come back to us if you'd like to discuss these details, until then there's not enough to go on sorry.
    – Chopper3
    Oct 6, 2015 at 12:52
  • I don't think creating separate VMDK's makes any difference if on the same PHYSICAL disk. The physical disk has an IOP limit. Once that limit is reached it doesn't matter how many VMDK's you create. Like @Chopper3 said, it could be striped across hundreds of disks so the the IOP capacity could be astronomical. VMs don't act like traditional servers where you would have the OS, IIS, DB partitions on separate drives for speed. VMs can use 1 datastore that's across 100 drives or just 1 drive (think RAID) with multiple VM's in that 1 datastore.
    – Travis
    Oct 21, 2015 at 14:09
  • I have one datastore that has 4 separate servers on them. One of those servers has 4 virtual disks (VMDKs) because I wanted to "partition out" the space. Has nothing to do with speed. That 1 datastore has 6 PHYSICAL drives in the SAN using a RAID10 configuration. Adding 5 more, separate VMDKs to that VM will not make it any faster.
    – Travis
    Oct 21, 2015 at 14:15

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