IOPS requirements

IOPS scaling, like bandwidth ( and to a lesser extent CPU scaling) is a very hard and exact science.

Just providing averages is deadly but designing to accommodate all the bursts is too expensive. So you will end up somewhere in the middle. That middle differs per customer. Taking averages can be risky. More experienced implementation partners will tell you about the importance of being able to accommodate bursts.

One important thing to remember is that windows xp is quite different from windows 7.

I get that, but can you at least give me some typical numbers? I've heard some tests requring as little as 3 IOPS per virtual desktop. Is that typical?

It also depends on the VM state. These number provide a good average:

• Boot: 25
  
• Login:  15
  
• Work: 5-10
  
• Logoff: 12
  

This depends on many factors and also the read/write ratio is very important!

• Boot: 25
• Login:  15
• Work: 5-10
• Logoff: 12

Is a good average.... in our testing I've found "work loads" to be anything between 3 and 15 for small - medium system usage. I've noticed Windows 7 booting ranges between 15 - 33 though.

I'm guessing with emerging technologies such as RemoteFX, IOP requirements will increase as more demanding applications will start hammering the disks.

Though all this depends on use case.

Other things can come into play to, disk type, storage type, raid level, speed, virtual disk alignment, etc etc.

I agree with Michel, averages are risky!

3 IOPs is generally windows twiddling it's thumbs wondering how to fill the time

Dan.

Hi Dan,

Did you get also get a chance to compare the read/write ratios for these different areas of a VD session?

Cisco has some pretty indepth white papers on this.  Granted...it's in reference to selling their UCS line, but good testing numbers nonetheless.

Hi Michel,

Nope... Using my own session on a Win7 VM and based on work load only, so no boot, login or logout ratios....

I would say R=20 - 30% and write is 70 - 80% over the course of a 2 hour session doing everything from web browsing to dreamweaver.

"They" say 20r - 80w is the average so I guess mines not to far off.

If I get chance I'll look into the different sections in the next week or so. - I've I remember

Cheers,

Dan.

Just to add... As we're using local storage for non-persistent VM's (which will count for 99.9% of our VM's), IOPs haven't been an issue for us as the servers we're using can cope with the IOPs per hosted VM. Our IOPs are spread across our hosts rather than central storage.

The headache comes when you have to make sure your SAN can cater for VDI VM's at a large scale and also make sure it's financially sustainable to scale out.

Of course this all comes down to architecture design, brick vs blade, etc...

I digress, thats for another thread

Cheers,

Dan.

Daniel, can you please share your server hardware configuration, i.e. make, model, CPU type & quantity, amount and type of RAM, number od local disks, type, speed, type of RAID Controller, amount of battery backed or flash cache, NIC Configuration, hypervisor type and version. I like to have cuistomer proven setups as reference to validate what we see in the lab.

Thanks.

Hi Patrick,

This is what I can tell you from home (not back in the office until Monday)...

Spec as follows:

----------------

IBM System x3650 M3 (2U)

NetXtreme II 1000 Express Quad Port Ethernet Adapter

12 X IBM 146GB 15K 6Gbps SAS 2.5" SFF Slim-HS HDD

2 X IBM 74GB 10K 6Gbps SAS 2.5" SFF Slim-HS HDD

IBM System x3650 M3 8 HDD Kit,1

Hot-swap SAS SATA 8 Pack HDD Enablement Kit (w/ 6 Gbps expander)

ServeRAID M5015 SAS/SATA Controller

ServeRAID M5000 Series Battery Assembly

2 X Intel Xeon Processor X5650 6C 2.66GHz 12MB Cache 1333MHz 95w

6 X 4GB PC3L-10600 CL9 ECC DDR3 1333MHz LP RDIMM

12 X 8GB PC3L-10600 CL9 ECC DDR3 1333MHz LP RDIMM

IBM UltraSlim Enhanced SATA Multi-Burner

Dual port 1Gb Ethernet Daughter Card,1

IBM System x3650 M2 & M3 R2 PCI-Express (2x8) Riser Card

IBM System x3650 M2 & M3 R2 PCI-Express (1x16) Riser Card 2

IBM 675W Redundant AC Power Supply

----------------

We're using Hyper-V R2 as the hypervisor which is installed on the 2 10k disks.

The VM's are on the 12 15K drives using Raid 10

We're getting between 40 - 55 Windows 7 VM's and 1 RDSh server which is catering for 20 - 30 users (and I think it can do more).

In our rough estimations (on a flip chart), hosting 30 - 35 VM's and the RDS VM with 10 - 15 users pretty much brakes even financially. Above these numbers, we see a ROI. Adding SAN to the mix is another story though....

We plan to add FX GFX cards to each server for RemoteFX (when it comes out) so that pushes the ROI down a little but it's still there.

Bare in mind we are public sector and do get good hardware/software discounts!

Cheers,

Dan.

Hi Dan,

Interesting. Do you know what the theoretical IOPS capacity is for the IBM 146GB 15K 6Gbps SAS 2.5" SFF Slim-HS HDD?

Hi Shawn,

Do you have a link to this paper?

Yep but not off the top of my head

I'll dig it out ASAP It's written in my notes... Why don't vendors ever have this info easily available on their site!

This was in a MS guide to scaling vdi for Win7

Is that after "tweaking" the OS first? or is it a non-molested OS?

It goes to show though that local storage is very very compelling

Cheers,

Dan