When you fall in love with Spanned Volumes

In our company, our major productive servers are hosted in vSphere as Windows-based virtual machines. Some of them need very big disks. Through the largest disk space supported in vSphere is 16TB (or maybe more, i dunno), I’m not interested to create such a big file in VMFS. It will be really a pain your *** when you have to move such a big file among datastores, even among data facilities by using portable hard drives.

Creating smaller disks instead of a big one for every Windows-based VM, IMHO.

Fortunately, Windows support to merge small disks as a big one, using dynamic disk function. There are 4 kinds of volume can be supported in such a condition: Spanned, Striped, Mirrored and RAID-5. You can consider them like JBOD, RAID-0, RAID-1 and RAID-5 functions in a simple legacy storage device.

Because data protection is existed in the SAN, Mirrored and RAID-5 volumes are not considered at all. Striped will make it a little faster when lots of virtual disks fight for limited IOPS resources within one datastore. But there is no way to extend any stripped volume (https://technet.microsoft.com/en-us/library/cc770938.aspx).

So, the useless volume format in a traditional world, spanned volume, is the best solution, maybe the only one. Next time when you need to create big virtual disks for Windows in any virtualization environment, don’t forget to consider using Spanned Volumes.

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