Why run VMware ESXi from a memory stick or SD Card?

Posted: 18/01/2010

This post has been prompted by a couple of questions I’ve had recently from readers and people I know asking “Simon, it’s all very well showing us how to install VMware ESXi onto a USB memory stick though why would I really want to do this in the real world?”

As you probably know VMware ESXi can be run from either disk, USB memory stick, SD Card or from SAN with the latter still deemed ‘experimental’ at this stage.

The following are a couple of basic reasons why I’d choose to install and run VMware ESXi from a USB key or SD memory card as opposed to local disk.  I’m not saying that memory stick or SD card based ESXi installs are better than those on local disk because as with most things it all comes down to ‘what is the best fit’ on a case by case basis.


VMware ESXi - HP BL490C - No DisksNo local disks on the ESX(i) host: Enterprise level servers such as the HP Proliant BL490c (Intel) or BL495c (AMD) are geared towards virtualization and so as to maximize physical memory space in the servers case it doesn’t come with internal disks. For these servers a hypervisor such as ESX(i) can either be booted from SAN (though this is only experimental at this stage for ESX(i)) or booted from a USB memory stick or SHDC memory card. That said, the only servers that tend to be diskless are blade servers. So if using rack mount or floor standing servers why bother you may ask…

More space on local disk: By installing and running ESXi from a USB memory stick you have 100% of any local disk for ISO storage, or if not using shared disk space via a SAN or NAS appliance then you can use all or part of this local disk space to run your VMs from.  The actual footprint of an ESXi installation is actually quite small (ie: just under 1GB for ESX 4.0) leaving plenty of local disk space available so with the capacity of modern disks (eg: 74GB+ minimum) the space it consumes is something of a non-issue. This particular point of running ESXi from USB memory stick or SD card as opposed to local disk is a little hard to argue though for me personally I like the flexibility in my lab environment of keeping my ESXi install and any local disk storage used for ISO’s or VMs separate. This means I can easily pull out one USB memory stick containing a version of ESXi and insert another containing a different version within seconds without impacting any ISOs files or VMs. To do this with a disk based ESXi install is much more hassle.

VMware ESXi SD CardRemote Site Deployment: If you are sending a server to a remote site direct from a supplier or manufacturer then it is easy to post/courier out a pre-configured USB memory stick containing ESXi complete with the ESXi configuration all set up and have someone with little or no IT skills plug it into the server to get things up and running. This combined with sending out pre-installed and configured VMs on a portable USB hard disk to the remote site, to be copied onto and run from the local disk of the ESXi host or shared storage, makes an administrators life much easier than trying to perform an install and configuration using virtual media over a limited network connection using an ILO, ILOM or DRAC.


There have been some interesting discussions going on regarding memory stick and SD based hypervisor based installations which can be found on these good posts here – well worth a read:

VMware ESXi 4: SD Flash in BL460c G6 – VCritical (Eric Gray) Note: Check out the photo of the new SD Slot located on the side of the BL460c – a nice feature in my opinion.

Blade Servers with SD Slots for Virtualization – Blades Made Simple (Kevin Houston)


HP VMware ESXi USB KeyA significant point of interest as mentioned in Kevin’s post is around HP’s u-turn in running ESXi from their own 4 GB USB Flash Media Key (Part Number 580385-B21) on the following popular servers in their Proliant range:

  • ProLiant DL380 G6 server
  • ProLiant DL385 G5p server
  • ProLiant DL385 G6 server
  • ProLiant BL460c G6 server
  • ProLiant BL465c G5 and G6 server

The reason given in this customer advisory is due to a “potential for erratic system” with the USB memory stick/key being in “close proximity to other components”.

When visiting the HP Proliant campus over in Houston in 2008 an engineer who was part of the Proliant DL380 G6’s design team informed that they had a number of instances of factory installed DL3xx’s with the ESXi memory stick where the memory stick would fall out of its internal USB port during transit from the factory to the client site.  This being part of the reason why they moved to an SD card slot located on the main system board.

So these are my reasons for installing ESXi onto a USB memory stick or SD card.  Why not let us know of any other reasons you can think of for installing ESXi on a USB memory stick or SD card as opposed to local disk – it’d be good to hear your thoughts and/or experiences.


About Simon Seagrave 706 Articles
Simon is a UK based Virtualization, Cloud & IT Technology Evangelist working as a Senior Technology Consultant and vSpecialist for EMC. He loves working in the ever changing IT industry & spends most of his time working with Virtualization, Cloud & other Enterprise IT based technologies, in particular VMware, EMC and HP products. As well as on this site, you can find him on Twitter and Google+


  1. Si

    A good article as always. I suppose the only thing to consider with using a USB flash drive or SD card is that you do not get the redundancy protection that do with local disks and a raid controller. On saying that though how often does a USB flash drive or SD card fail?

    Just my quick response


    • Hi Martin,

      Thanks for the comment. 🙂

      That’s a good point re: redundancy of disk versus USB flash drive though as you rightly point out the failure rate on USB flash drive/SD cards is generally pretty low. This single point of failure should be factored in however to the solution if the ESXi host is not being run in a resilient cluster with HA, etc. Once ESXi has loaded much of what it does it then memory based thereby minimising the read/writes on the actual storage device.

      It’d be interesting to find out what the average failure rate on USB memory sticks/SD cards actually is.



  2. Simon – great post, thanks for keeping the ESXi discussion going. Also appreciate the link to my blog posting. Seeing how VMware is even moving their internal hosts to ESXi very soon, I think that ESXi is the wave of the future.

  3. Simon,

    Could not agree more

    ESXi from an SD/USB slot is an awesome idea, single point of failure should not be an issue, as ESX should always be built out with redundancy in mind, and nothing quite beats having 16 blade servers without a single moving part in them (all the moving parts are in the chassis at that point, and fully redundant!)

    By using ESXi your also lowering your attack footprint significantly

    Nice article, and I love those new SD slots on the G6 blades 🙂

  4. I dont no if your readers will be intrested but I was looking for a 128GB SDHC Memory card and I was nuts to try and buy on on Ebay, not a good idea, well not for me. I came across a web site called SD Card World @ http://www.sdcardworld.co.uk/ , not seen them on the web before. I contacted them and asked them if they could supply this type of SDHC card ie 128GB SDHC, They did not have it in stock but within a week they delivered the card at a great price and it is 100%.

    Just a little info from a very very happy man, top web site.



  5. Hi, interesting read. For me, the best thing about running on a memory stick is that it means no pointless HD generating heat. All VMs can be stored on a cheap NAS device (e.g. Netgear), over NFS or iSCSI, and are therefore redundant, easy to back up, etc. A good discipline and a cheap way to get more secure environment, even if it’s only for one-man-band dev VMs. Sure, you could do that in a server, but with a NAS you get a lot more free: secure file serving, streaming, remote access, easy configuration, etc.

  6. I’ve found in my experiance that using SD card’s as a ESXi boot medium is unreliable and painful, With local disk atleast you get redundancy with a raid array and get a clear indication when something has failed. We had a SD card fail and the host would not to respond, however it would boot up ok. I believe local disk is STILL the most reliable way to run ESX, After all a systems only as strong as its weakest point.

  7. I agree, Father Time – Why are so many websites and blogs undated? I’m trying to do some research here and I’m left wondering whether running ESXi from SAN is still experimental or have things moved on significantly since the blog was written.

  8. If you put the hypervisor on a USB and data store on SAS HDs, would this be a safe practice? I thought usb’s have a limit of reads and writes and therefore would not be a good candidate to serve the hypervisor.

  9. One other question if I installed the hypervisor on slow 5400 rpm sata HD but the datastore on a fast 15000rpm sas drive would the 5400 rpm drive effect performance?

      • Hi Guys,

        I thought I might get the answer quickly by directly asking one of you. My question is, If I install ESXI in the local disk of the server, will be able to use rest of the disk space in local disk for data storage i.e. VM OS storage? As we all know, ESXI installation takes just a tiny space (<500 Mb) and My local disk is a Raid 10 410Gig disk.

        Thanks and Best Regards!

  10. Hi There,

    I have one question, If i install VMware ESXI in local disk, which is RAID 1+0 410 Gig Disk, As ESXI installation only takes very small portion of the disk space i.e. less than 500 Mb, will be I able to use the rest of the disk space for data (virtual machines) storage? Or will the ESXI takes the whole disk space and need to have different disk all-together for data storage?
    Thanks! Would really appreciate if someone could answer asap, as I have to setup this server with few VM in my work within this week.

    Best Regards!

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