I've been working with Windows Azure and Amazon Web Services EC2 for a good many months now (almost getting to the years range) and I've seen something over and over that seems troubling.

With AWS & Linux I commonly get instance startup times with EC2 around the 1-3 minute range.

With AWS & Windows OS on an EC2 instance it often takes 10-20 minutes.

With Windows Azure Web or Service Role I often get anywhere from 6-30 minutes waiting for a role to startup. I assume of course this involves booting up a windows instance somewhere in the fabric.

I know there has always been tons of FUD about windows vs. Linux, but I'd really like to know why it is that Windows 08 or 03 boots so much slower in the cloud than Linux. Any specific technical information regarding this would be greatly appreciated! Thanks.

  • are these new servers being started up or basically reboots? If new then its more then likely the provisioning service thats hanging things up and in my case I don't really care about provisioning times. – tony roth Oct 29 '10 at 18:57
  • Are those times for instances [e.g. a basic OS install] or does it include automated setup and configure tasks? – Till Oct 30 '10 at 21:50
  • hmmm, the longer end of the range is near the provisioning range, but generally the reboots/boot ups take about as long as stated above. – Adron Oct 31 '10 at 16:56

Mark Russinovich (of Sysinternals fame) had a nice talk on the recent Microsoft PDC conference in which he explains what is happening under the hood of Windows Azure. If you don't want to watch the whole video or skim over the slides - there are actually a lot of things happening besides simply booting up a VM when you request a new instance.

Of course the above is specific to booting a Windows VM in the Azure cloud. I have no experience with Amazon's offering but I assume they're also doing a bunch of infrastructure-related operations before starting a new instance. There's no arguing that generally a machine boots up faster with Linux than with Windows, but I would attribute the considerable boot-time difference in the cloud to infrastructure specific operations.

  • Just listened to the talk. Very cool, that offers some good insight. – Adron Nov 11 '10 at 0:50
  • It's a nice talk indeed, hope you enjoyed it. – tishon Nov 13 '10 at 16:46
  • Just realized some of the bits about why Azure takes so long. I'm working to one day get a blog entry detailing these specifics. Should be a good write up. :) – Adron Mar 14 '11 at 15:14
  • Make sure you share the link ;) – tishon Mar 16 '11 at 9:04

There is a very interesting paper (easy to read) about the vm startup time in the cloud. It includes EC2, Rackspace and Azure. The answer seems to be the VM image size.



  • Whilst this may theoretically answer the question, it would be preferable to include the essential parts of the answer here, and provide the link for reference. – Scott Pack Sep 21 '12 at 2:25

The majority of time spent by Windows instances during boot is sysprep and generating SIDS. On EC2, if you were to create an AMI and try launching an instance from that image (w/o sysprep), you'll notice the startup is much quicker.

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