To make a long story short, I am wondering if it is unwise to use large thin .vmdk's for a nas VM? I am planning on backing up to external 2TB drives (very small business), keeping one offsite at all times.
I could use a poweredge 840, but the fileserver is so lightly used, it seems like a waste. The company has an ESXi server that could store the fileserver disks.
Regarding the backups, would I be better off using cron+rsync and passthrough to USB using the native disk, or should I make a datastore and backup the .vmdk files? Also, there isn't any budget for software.
Best Answer
In my opinion both the alternatives you present for backup are a bad idea. I highly doubt hot-plugging USB hard drives was in the design brief when VMware designed the datastore system. Yes you can dismount datastores, but I'm not sure ESXi supports using USB devices as datastores anyway (I think you'll find the embedded OS can't mount volumes from USB devices).
USB passthrough for storage devices is available in ESXi, but you have to shut down the VM to detach it cleanly. Again, using this mechanism for routine backup is a bad idea as it's highly inconvenient to do cleanly. I've also experienced data corruption while attaching a USB HDD to a CentOS 5.5 VM on ESXi 4.1 for a migration... I wouldn't trust it for backup.
A cheap NAS gets my vote.
Regarding using large VMDKs I'm not aware of any specific risks of that size, but it doesn't seem like a great idea to use a thin 1TB vmdk for a NAS, especially since there will presumably be a lot of writes.