ESXi disk size requirement?

I’ve seen this question passing by a couple of times now and I found myself going through the document to dig up the reference. I thought it would come in handy to document it:

Q) What is the disk size requirements for ESXi installable?
A) The minimal required disk size is 5GB (Page 24, ESXi Installable and vCenter Server Setup Guide), recommend is 6GB (KB:

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    1. Brandon says

      OK a sort-of unrelated question, but I saw this statement in the setup guides (its the same for ESX or ESXi):

      “2GB RAM minimum. For upgrades, 3GB RAM is required if the ESXi host is managed by vCenter Server.”

      2GB of memory is the minimum, I understand that, but what does the “For upgrades,” mean? 3GB is required if managing with vCenter, or only if you upgraded and intend to use vCenter? What if I loaded a host with esx(i) from scratch and then managed it with vCenter? Is 2GB or 3GB required then?


    2. Nathan says

      The thing is you usually have at least 2x 136GB HDD installed locally, I’m working on 2.5″ SAS here. partition this to say 50GB on a mirror for redundancy and your are away. nothing wrong with leaving a little FAT (excuse the pun) :-). Even with ESXi having some extra space for update files etc can always help at some point.

    3. says

      I brought this up with VMware @ vmworld and didn’t get much of a response, but you can install ESXi on 1GB USB drive with no problems. I run most of my servers with 4GB drives but the Dell R-series servers come with 1GB cards. Never had any issues with either. Would love to hear from VMware on an official statement on this…

    4. Brandon says

      @Duncan boot from SAN on ESXi switched from experimental to fully supported as of 4.1, so booting over iSCSI is supported assuming you have a hardware based iSCSI HBA.

    5. Brandon says

      Thanks for the clarification, I learn something new everyday. ESX and ESXi appear to be complete opposites in how they support iSCSI boot.

      Once ESX finally goes away it’ll be easier to keep track of, that is for sure.

      BTW I had to figure out what iBFT is, I had no idea. If it saves anyone time it is “iSCSI Boot Firmware Table”.

    6. Ivan Marshall says

      Well .. this is definately interesting ..

      The new Dell R910 that we are using (specifically designed for virtualised environments) comes with 2 x 1GB SD cards (mirrored).

      And I have managed to install ESXi with no issues and no complaints from the ESX.

      I even enabled local tech support mode, and did a comparison with df & vdf (using a 1GB SD install vs a install on a 146GB HDD); there was zero difference.

    7. Brandon says

      I’m trying to figure out how much you’re kidding, or if there is something about being “stateless” by your definition that is not supported.

      I think stateless would be NO physical equipment at all, and we can run in the clouds that are our minds, but that is just me ;).

    8. Carl Skow says

      Many vendors wrap the idea of statelessness along with the idea of a profile or persona that allows you to boot from some central storage LUN on any server so that you can boot the exact same server on alternating pieces of hardware.

      We’ve been talking a bit about the pure stateless idea where if you lose the device ESXi is running on (SAN boot, local disk, USB, etc) on the piece of hardware you’re running ESXi, the system would crash normally. However, a stateless build will continue to operate as ESXi and is not dependent on the disk/storage itself while residing 100% in memory. What Duncan is talking about is likely what we’re going to be seeing in the future. That is not supported today, but given time will likely be a feature in the future. It can be done today with a little bit of hacking and a lot of “hope I don’t have to call support….”.

    9. Brandon says

      Well, I agree with Duncan’s assertion (I have to play nice, what if I ever take the VCDX and he’s on the panel?! :)). I also think there are several definitions of what “stateless” is, or at least several things which can get you closer to near perfect-world. Still, now that ESXi supports boot from SAN I think a lot of orgs will do this because of the benefits. It might not be perfectly stateless, but probably as close as you can get while maintaining your support.

    10. Gurusimran Khalsa says

      Thank you for the great blog Duncan. I also really enjoyed meeting you briefly at vmworld sf in the labs. I’m very interested in the same thing a couple of other comenters are, I have Dell r810 servers with dual 1 gb sd cards and no local storage. Is this unsupported? Do I need other local storage? If so, what for? Thank you in advance for any input.

    11. Gurusimran Khalsa says

      Thank you! I really appreciate it. Not sure if you’ve watched/listened to it but there is a great session from vmworld on esxi by Oliver Cremel that has taught me a lot about the details of esxi (including some issues that come up with booting from a 1 gb sd card – log retention for one.)

      All the best. Thank you again for the great blog and your help.

    12. Ford Donald says

      The labs we built for VMworld exclusively use ESXi. For those hosts, I utilized a 1.2G boot volume with no other storage local (all labs carry at least one iSCSI target).

    13. says

      I am confused. If the installation requires 5GB, how can we get away with smaller SD cards and what not. Are we doing something thats not supported by VMware?

    14. Eric says

      From the vSphere upgrade guide. Looks like if you don’t have 5Gb, it will use space from RAM.

      Installing ESXi 5.0 requires a boot device that is a minimum of 1GB in size. When booting from a local disk or
      SAN/iSCSI LUN, a 5.2GB disk is required to allow for the creation of the VMFS volume and a 4GB scratch
      partition on the boot device. If a smaller disk or LUN is used, the installer will attempt to allocate a scratch
      region on a separate local disk. If a local disk cannot be found the scratch partition, /scratch, will be located
      on the ESXi host ramdisk, linked to /tmp/scratch. You can reconfigure /scratch to use a separate disk or LUN.
      For best performance and memory optimization, VMware recommends that you do not leave /scratch on the
      ESXi host ramdisk.