Blue Chip News & Opinions
Improved Back End SAN Storage in a Large VM Estate
One of the biggest headaches for technical people using large VM estates is the back end storage.
Here is why…
With VMware’s Thin Provisioning utility a techie is easily able to eliminate the need to dedicate full capacity of the hard disk of a VM upfront.
The Old Method…
VM is built and 50GB of disk space is “thick” provisioned to the server. This means 50GB of the SAN storage is 100% committed to the server.
This method means you very quickly run out of disk space.
The Newer Method…
VM is built and 50GB of disk space is “Thin” provisioned to the server. This means what is required at that moment in time for the VM is then committed to the SAN storage and the rest is simply kept in reserve and can be used elsewhere.
This method is great but has its flaws; one being the ability to govern exactly how much disk space has been allocated to each server.
Below is a graphical presentation of Thin and Thick Provisioned Disks (www.vmware.com)
As in the examples; the danger of the newer method is that simply making sure you don’t over allocate disk storage becomes extremely difficult. You would need to monitor each virtual machines disk space growth and then make sure you have enough SAN space to facilitate it.
In large VMware estates this is a pain as you ordinarily have a number of technical staff building VM’s so governance of such is impossible; not to mention keeping an eye on how much each VM is growing day by day.
The old method on the other hand combats this issue but of course is not very efficient. You are allocating for arguments sake 50GB of disk space to a VM which may only ever use 10GB in its life time. This then means there is wastage of 40GB; trends have shown of a 1TB disk being used by VMware thick provisioning there is wastage of 25% (250GB).
How Blue Chip Combat This…
There are a number of ways to combat this headache.
The first is to simply keep a record of every VM built and how much disk space is allocated. Then use a third party tool to monitor disk usage of each VM.
This method is extremely tedious and time consuming and lets face it who is going to spend the time doing this? We as techies have better things to do!
The second option is to have the storage do this work for you!!
With the birth of IBM’s v7000 VMware administrators are now able to allow an intelligent SAN to do the hard maths for you.
IBM® v7000 Thin provisioning, will actually giving you a graphical presentation of how much storage has been allocated and how much is available.
The new v7000 also allows for alerting to be set up so that when your storage is close to capacity you are able to simply add more disks or another draw.