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ESXi Install Location Best Practices

I am going to be installing ESXi on a server (for connection with a Vcenter).

It has 2 Raid 5 Sets (1 TB of Fast SAS Disks, and 1 TB of Regular Sata)

I was planning on installing and running ESXi off of the SAS Fast drives and still using these drives as part of the VMFS Datastore location (as well as the sata drives).
However, a colleague noted that it was a best practice to not install ESXi on the same disks as you will be using for VMFS datastores. Instead he suggested I install ESXi to an external USB flash drive and boot off of that, leaving the hard disks completely separate.
Is this a best practice or simply unnecessary?

Avatar of Andrew Hancock (VMware vExpert PRO / EE Fellow/British Beekeeper)
Andrew Hancock (VMware vExpert PRO / EE Fellow/British Beekeeper)
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Personally, I would keep all local disk, for the VMFS datastore.
if this is not possible, I would use SATA for the installable copy of ESXi, and use the Fast SAS disks for your VMFS datastore. SAS will perform better than SATA.
Please note that during the GUI based installation, you will not be able to specify the block size of the datastore (it installs with 1 MB Block size which can sustain a maximum file size of 256 GB on the datastore)

Only scripted installations support the modification of block sizes (1 MB / 2 MB / 4 MB / 8 MB)

Personally, I would install ESXi v4.1 on a USB drive (preferable a 4 GB or 8 GB drive)
Don't get mad when I say this Arun...

It is widely understood that in the installed esxi versions on USB or CF Cards do not use more than 2GB of space, and you cannot use any more unless you script it as Arun stated.  

So for a default install through the text/gui you would never need more than a 2GB USB stick as the rest would be wasted (money as well as space [ UNLESS YOU DO A CUSTOM SCRIPTED INSTALL ])

We use IBM Servers with an internal USB connection for all of our servers.  We only use ESXi 4.1 installable on USB 2GB Sticks and have 2 available at each site in the off chance we have a server crater.  

So to answer your first question, yes usb installed ESXi is a best practice and recommended.  It is certainly not unnecessary although you know your environment best.  If you are going to be moving to SAN/NAS storage for VMs and the local storage is going to be wasted anyway then your mileage may vary.


Just make sure you use GOOD Quality USB sticks, not the rubbish ones.

and for DR, use Winimage to make a backup of the USB sticks, and put the 2GB image somewhere safe.

you can then use CLI or vMA to backup the configuration of your host ESX server, because if a USB stick should go bad, you can quickly restore the image using Winimage, and then restore the configuration using CLI or vMA.

We generally use good quality HP v100w sticks. (and these were similiar to the original ESX 3i sticks before HP stopped shipping them!)
Just for the sake of argument.  even if you do not make images of your USB Sticks (we don't) it only takes 20 minutes for the install and then a quick profile push and your back.

There are a lot of ways to skin this cat, but Hanccocka is totally on the money when he recommends good sticks... 75bucks is a small price to pay for a 2GB stick if you need it to work 5 9's