snapshots

How much free space is needed on a LUN for VMware?

Hi folks! One of the common questions you might find in the virtual world with VMware is how much free space do I leave on a LUN? When is it not enough?

A common mistake is to think you only need enough free space for the size of the VM itself and not much more. Well if you do that you’ll quickly find out the hard way that you should have allocated more. You see VMware needs space for things such as snapshots and space for emergency situations where you might need the space for shuffling things around from LUN to LUN.

The general consensus for free space on a VMware LUN is 10% to 20% free space. This isn’t just for snapshots, but also to account for any emergencies you might have to deal with on a VM where you need the free space. So if you don’t have  10% to 20% free space, then essentially you should treat the disk as full for all intents and purposes. 20% can be considered on the conservative side but it doesn’t hurt to be cautious.

I have heard people say 10% to 15% is good enough but only if you have very strict snapshot policies to ensure that you are monitoring the disk space closely.

-RP

VMware snapshots, live it, love it, learn it!

Hi folks, here’s a standard feature of VMware that a lot of people take for granted that I thought would bear mentioning. Snapshots!

So you have an application or patch you want to install and you don’t know what effect it will have on your server. What do you do? Take a snapshot! With VMware you have the ability to take a snapshot of your OS at that point in time and then make whatever changes you desire. After your changes are made you can check to see if everything is working. If there are issues you can just select the snapshot and revert back to where you were before.

I find it quite surprising how many people actually have VMware and forget to use this feature as if they’ve forgotten it’s even existed! Snapshotting can be your best friend when doing upgrades, don’t forget it!

-RP