Why WAFL is at the core of unified storage

A while ago, in part a reaction to the baffling claims made by EMC about Celerra NX4, I explored what is unified storage. And in particular, I tried to expose the fact that EMC had redefined he value proposition of unified storage from:

A storage manager who wants a single device to support all protocols should not have to buy or setup more than one device, should not have to learn different tools to perform the same task, and should not have to understand different replication mechanisms to do DR or backup should buy a unified storage device.

to:

So if you are a storage manager who wants a storage device that requires multiple distinct devices to be configured, that management for common tasks involves multiple distinct tools, that has multiple protocol and device specific replication strategies, then the Celerra NX4 is that storage device.

Because of this EMC distortion, NetApp has decided to take back the definition to mean what we know it means.

When I wrote up that series, I concluded there were two definitions of unified storage, a unified storage device and a unified storage architecture.

And to remind folks a unified storage device has the following attributes:

1. A piece of hardware that has CPU, Memory and disk
2. That supports FC, iSCSI, CIFS and NFS
3. That has a common management console for all storage functions that are not protocol specific
4. Has a single replication mechanism that is independent of protocol

And a unified architecture has the followed attributes:

• Each device is a unified storage device
• Each device may have different amounts and kind of CPU and Memory and Disk but components must be interchangeable.
• The management model for each device is the same.
• Any device can replicate storage to any other device

And I drew this picture for what a unified storage device should look like:

But I never really explained what enables NetApp to deliver this value.

If you read my series on WAFL, you'll find this picture:

And the answer is fairly obvious: WAFL.

Because of the way we layered the protocols on top of WAFL, and implemented RAID as a software layer below WAFL we offer a single hardware and software stack for all kinds of data access enabling us to have a single piece of hardware (1) that supports all protocols (2).

Because all space management is done in WAFL ,we have a consistent way to manage space across every protocol. You provision and manage storage space in the same way. Because of the way RAID is layered below WAFL all of your disk management is done in the same way. We can, therefore, offer a common management console for all storage functions (3).

Because all reads and writes go through WAFL and because all space is managed through WAFL we can have a single replication mechanism for all protocols (4).

And finally because all of our hardware platforms run the same software, we offer a unified storage architecture for our FAS systems.

If there is a point to this blog post, it is that a unified storage device and architecture are not bolted on features, or marketing spin, but fundamental architectural decisions about how storage systems are built.