I've got a Dell Poweredge server with Esxi 4.1 installed and 3 virtual machines running Windows Server 2008 R2. One of the VMs which is running Exchange 2010 and is running out of disk space. I have consequently added additional hard disks with RAID1 giving me another 930Gb. The existing Datastore is 900Gb made up of 3 hard disks on RAID5. My question is, should I extend the existing datastore's capacity with the new drives or is it best to create a new 930Gb datastore to create the new virtual disks for the Exchange Server? Also, if I create a new Datastore, should it be with a 1Mb or 2Mb Block Size?
Any help and advice would be greatly appreciated.
Thanks in advance.
Extents - if at all - should only be used with same storage tiers, i.e. you shouldn't extend a RAID5 datastore with RAID1 volume. I'd suggest you create a new datastore. The required block size depends on the maximum virtual disk size. Anyway, in the past I usually used either the 1MB block size, or the 8MB block size to keep things simple.
Best option is to create a new datastore , and if you want you can migrate the VM to the newly created DS,
Block size depends upon your serve usage and performance
Usually as per best recommendations for Virtualizing Exchange Server it is best to provide better parallelism of storage I/O, equally distribute storage devices among the available disks using SCSI controllers. I would recommend to create a new datastore and present a new disk to the Exchange server VM. The block size would depend on the maximum file size that will be created, for 1 MB it is 256 GB of maximum file size or and for 2 MB it is 512 GB of maximum file size. As per your current configuration, you may use format the datastore with 2 MB block size.
Thank you for all your replies and feedback which is very helpful indeed. I will create an additional datastore and add another hard disk to the Exchange VM. Will this increase the file size of the VM on the original datastore which is with 1Mb Block Size? Or will it just create a new file on the new Datastore.? I'm worried about space issues on the original datastore.
Adding the virtual disk will not require additional space on the original datastore (maybe a few Bytes). However, if you are going to add a virtual disk larger than 256GB to the VM, you will not be able to create snapshots anymore, because ESXi 4.1 creates the snapshots in the VM's "home" folder by default. What I would suggest is to completely move/migrate the Exchange VM to the new datastore, which will allow you to either add an additional virtual disk to the VM, and/or increase the current virtual disk's size.
Thanks for your advice André. In that case I think I'll go for 1Mb block size and 250Gb virtual disks on the new datastore so that I can use the snapshot facility. To be honest with you, I'm a bit scared of moving VMs around.
Your advice has been a great help.