For those not in the know, Dell recently released a new firmware version for the MD32xx and MD36xx series. The two big features are VAAI support and Dynamic Disk Pools.
VAAI is the VMWare hardware-acceleration API. The MD’s support hardware accelerated locking, which is a huge freakin’ deal. This means that locking operations only lock the needed blocks during a VM operation, and not the whole LUN. This means that you can create and manage a few big LUNs with a lot of VM’s per datastore, instead of a bunch of tiny LUNs.
Here’s a great article on VAAI: Why VAAI?
Dynamic Disk Pools
DDP is an interesting concept. It’s kinda like RAID 6, but instead of choosing a specific hot spare, you choose how many physical disk failures you want to tolerate. The system pools all the disks together, and uses all the spindles, but reserves a small amount of space on each disk in the pool to tolerate failures.
- You get to use all your spindles instead of reserving a hot spare.
- You can create larger disk pools than would be safe with RAID6.
- You can tolerate n-number of failures, where n is the amount of disk space you’re willing to reserve.
- Rebuilds are about 4 times faster.
- DDP’s are not as fast as RAID6 for fully-sequential writes.
- It’s new, and that might freak people out.
Here’s a video from Dell on the new feature:
- (youtube) Introducing Dynamic Disk Pools from Dell
- (youtube) Dynamic Disk Pools on Dell’s PowerVault MD
- (pdf) Dynamic Disk Pools Technical Report
I’m using both features now; they’re sweet.