Lots of VMs fight for one HD - problems?

[scottgus1]

I have about 5 XP VM's on my Core-I7 3.4GHz Windows 7 Professional 64bit 16GB memory machine, with alll the VDIs on one RAID-1'd 1TB drive. When I boot all of them at once, they are slower on booting than if I did them one at a time. I haven't noticed problems with this so far, but I just wanted to see what might happen:

If several big VMs (XP, Windows 7, etc.) have their virtual hard drive files on one physical hard drive, and they all try to access their virtual drives at once, such as when booting, all the VM's are fighting over the one set of heads on the physical drive, and they'll all have to share. Could there ever occur a time-out or some other problem where one VM complains and has problems because of not getting quick enough access to its virtual drive?

[Sasquatch]

No, it won't influence the VMs in such a bad way. They just slow down because the hard drive(s) can't deliver the required IOPS in the set time. It's the same as when you would extract one 100 MB archive, or a dozen of them at the same time. Extracting one will take mere seconds, extracting a dozen can take over a minute.
See it like downloading a big file. You have a 2 Mbit connection, you neighbour has a 20 Mbit connection. The server you get the file from can handle it, but your internet connection isn't fast enough to get it in the same time as your neighbour. It just takes longer to get to the same result.

[scottgus1]

Thanks, makes sense.
BTW, what did you retire from, & what's OSSO?

[Sasquatch]

Check the announcement at the top of this forum to learn about OSSO. You will have to deal with it too, if you choose to.

[scottgus1]

OK, I get it, Oracle Single-Sign-On.
I went thru that this aftenoon, and got an oracle account. But I can't get the login button (https://www.virtualbox.org/login) to recognize my nicknake 'scottgus1' and my password. Neither the forum password or the Oracle password I signed up with work. At least I'm still able to post... For now...

[Perryg]

The forums have not converted yet. Just VirtualBox.org and bugtracker.
Have you ever setup an account on those? That server used a different login.

[smartysmart34]

[quote="Perryg"]The forums have not converted yet. [/quote]

And to be honest: The day that happens I'll be out of here. I am not going to sign up with address / phone and other information being mandatory just to post in a support-forum of a free software.
Ain't gonna happen.

Cheers,
Martin

[scottgus1]

"Forums haven't converted yet."
That explains it. Thanks, Perry, I was wondering if I was doing something wrong. I've not signed up for anything but the forum so far.

[vbox4me2]

With a windows Host you need to set it to optimize memory use to system cache and start each VM with a 30 second interval, after that you also need cacheset/cachecontrol tools to keep the Host under control. Linux seems to handle this much better but this can also be achieved with windows as along as you tame its (own)cache use. Fast SaS disks and a good cached controller should be obvious like a MegaRAID SAS 9265-8i/4i.

[scottgus1]

Vbox4me2, I googled that memory system cache suggestion and found this blog:
http://essayboard.com/2011/08/22/increa ... windows-7/
Is this what you mean?

I also found 'cacheset' on Sysinternals' site.

Right now, my Windows 7 host is running well even with 4 VMs running at once. I see it makes sense to let each VM boot woth a delay in between. Usually I am more patient. What will applying this memory tweak provide?

[vbox4me2]

It solves the chicken and the egg problem when it comes to memory management, you need to let the Host assign cache ram as the Host wants/needs, however with system caching it will handle all ram which can starve VM's so you need to limit the Host as to how far it can go, do note that this tool needs to run constantly or the Host will overrun the max values over time and of course you need to experiment which values work best and how often to re-enforce them.

[scottgus1]

Okeedoke. Thanks, all, for your thoughts, I'll keep it all in mind...