something that behaves like a local file system (without the gotchas of NFS like a lack of delete on close), but I don't have to snapshot and create new volumes and issue file system expansion commands to grow a volume. I want seamless and automatic growth.
Wouldn't EBS w/ thin provisioning get you most of this? Just create a massive volume, and you get billed for the space actually used. (and the volume size could also function as a limit on your bill.)
Yes, good point. This would provide effectively "infinite" backing storage. There might be some hurdles to overcome, though. For example, when you delete a file, will EBS know that the blocks are now free and thus can be decommissioned? This might mean the whole stack needs to support things like TRIM. I'm not sure the rest of the stack is smart enough yet. I'd love to hear from a storage/FS expert on this.
Edit: coincidentally, I just saw this article about XFS which observes the following:
"Over the next five or more years, XFS needs to have better integration with the block devices it sits on top of. Information needs to pass back and forth between XFS and the block device, [says Dave Chinner]. That will allow better support of thin provisioning."
https://lwn.net/Articles/638546/
The reason I suggested it is because thin volumes are well understood, so the issues are straightforward... and it's been implemented in many products (lvm; virtually every san; xenserver & vmware; etc). So there really shouldn't be many surprises if amazon were to implement it.
And yes, trim is used to mark blocks as free.
Honestly, it's so widespread, I would be surprised if Amazon weren't already using it to over-commit ebs.
Wouldn't EBS w/ thin provisioning get you most of this? Just create a massive volume, and you get billed for the space actually used. (and the volume size could also function as a limit on your bill.)