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Category: Flash

I started working with flash in 2006 — fortunate timing as flash was just starting to take hold in the enterprise. I started asking customers I’d visit about flash. I’ll always remember the response from an early adopter when I asked about how he planned on using the new, expensive storage, “We just bought it, and we have no idea.” It was a solution in search of a problem — the garbage can model at play.

Flash has evolved significantly since then from a raw material used on its own to a component in systems of increasing complexity. I wrote recently about the various techniques being employed to get the most out of flash; all share the basic idea of trading compute and IOPS (abundant commodities) for capacity (still more expensive for flash than hard drives). The ideal use cases are the ones that benefit most from that trade-off, ones where compression and dedup consume cheap compute cycles rather than expensive space on the NAND flash. Flash storage is best with data that contains high degrees of redundancy that clever software can squeeze out. With those loose criteria, it’s been amazing to me how flash storage vendors have flocked to the VDI use case. It’s certainly well-suited — big on IOPS with nearly identical data from different Windows installs that’s easily compressed and deduped — but seemingly every flash vendor has decided that it’s one part — if not the part — of the market they want to address. Take a look at the information on VDI from various flash storage vendors: Fusion, Nimble, Pure Storage, Tegile, Tintri, Violin, Virident, Whiptailthe list goes on and on.

I worked extensively with flash until leaving Oracle in 2010 when I decided to leave for a start up. I ended up not sticking with flash precisely because it was — and is — such a crowded space. I’d happily bet on the space, but it was harder to pick one winner. One of the things that drew me to Delphix though was precisely its compatibility with flash. At Delphix we create virtual database copies by sharing blocks; think of it as dedup before the fact, or dedup but without the runtime tax. Creating a virtual copy happens almost instantaneously saving tremendous amounts of administration time, unblocking developers, and accelerating projects — hence our credo of agile data. Unlike storage-based snapshots, Delphix virtual copies are database aware, provisioning is fully integrated and automated. Those virtual copies also take up much less physical space, but with as many or more IOPS hitting the aggregate of those virtual copies. Sound familiar yet? One tenth the capacity with the same workload — let’s call it 10x greater IOPS intensity — is ideally suited for flash storage.

Flash storage is best when clever software can squeeze out redundancies; Delphix is that clever software for databases. Delphix customers are starting to combine our product with their flash storage purchases. An all-flash array that’s 5x the $/TB as disk storage suddenly becomes half the price of disk storage when combined with Delphix — with substantially better performance. We as an industry still haven’t realized the full potential of flash storage. Agile data through Delphix fills in another big piece of the flash picture.

For a short while, I ran the flash memory strategy at Sun and then Oracle, so I still keep my ear to the ground regarding flash news. That news is often frustratingly light — journalists in the space who are fully capable of providing analysis end up brushing the surface. With a tip of the hat to the FJM crew, here’s my commentary on a recent article.
NetApp has Hybrid Aggregate drives coming, with data moved automatically in real time between flash located next to the spinning disks. The company now says that this is a better technology than PCIe flash approaches.
Sounds interesting. NetApp had previously stacked its chips on a PCIe approach for flash called the performance acceleration module (PAM); I read about it in the same publication. This apparent change of strategy is significant, and I wish that the article would have explored the issue, but it was never mentioned.
NetApp, presenting at an Analyst Day event in New York on 30 June, said that having networked storage move as it were into the host server environment was disadvantageous. This was according to Stifel Nicolaus analyst Aaron Rakers.
1. So is this a quote from NetApp or a quote from an analyst or a quote from NetApp quoting an analyst? I’m confused.
2. This is a dense and interesting statement so allow me to unpack it. Moving storage to the host server is code for Fusion-io. These guys make a flash-laden PCIe card that you put in your compute node for super-fast local data access, and they connect a bunch of them together with an IB backplane to share the contents of different cards between hosts. They recently went public, and customers love the performance they offer over traditional SANs. I assume the term “disadvantageous” was left intentionally vague as those being disadvantaged may be NTAP shareholders rather than customers implementing such a solution.
Manish Goel, NetApp’s product ops EVP, said SSDs used as hard disk drive replacements were not as interesting as using flash at the disk layer in a Hybrid Aggregate drive approach – and this was coming.
An Aggregate is the term NetApp uses for a collection of drives. A Hybrid Aggregate — presumably — is some new thing that mixes HDDs and SSDs. Maybe it’s like Sun’s hybrid storage pool. I would have liked to see Manish Goel’s statement vetted or explained, but that’s all we get.
Flash Cache in the controller is a straightforward array read I/O accelerator. PCIe flash in host servers is a complementary technology but will not decentralise the storage market and move networked storage back into the host servers.
Is this still the NetApp announcement or is this back to the journalism? It’s a new paragraph so I guess it’s the latter. Fusion-io will be happy to learn that it only took a couple of lines to be upgraded from “disadvantageous” to “complementary”. And you may be interested to know why NetApp says that host-based flash is complementary. There’s a vendor out there working with NetApp on a host-based flash PCIe card that NetApp will treat as part of its caching tier, pushing data to the card for fast access by the host. I’d need to dig up my notes from the many vendor roadmaps I saw to recall who is building this, but in the context of a public blog post it’s probably better that I don’t.
NetApp has a patent in this Hybrid Aggregate disk drive area called “Mechanisms for moving data in a Hybrid Aggregate”.
I won’t bore you by reposting the except from the patent, but the broad language of the patent does recall to mind the many recent invalidated NetApp patents…
Surely this is what we all understand as auto-placement of data in a virtual storage pool comprising SSD and fast disk tiers, such as Compellent’s block-level Data Progression? Not so, according to a person close to the situation: “It’s much more automatic, real-time and granular. Compellent needs policies and is not real-time. [NetApp] will be automatic and always move data real-time, rather than retroactively.”
What could have followed this — but didn’t — was a response from a representative from Compellent or someone familiar with their technology. Compellent, EMC, Oracle, and others all have strategies that involve mixing flash memory with conventional hard drives. It’s the rare article that discusses those types of connections. Oracle’s ZFSproducts uses flash as a caching tier, automatically populating it with useful data. Compellent has a clever technique of moving data between storage tiers seamlessly — and customers seem to love it. EMC just hucks a bunch of SSDs into an array — and customers seem to grin and bear it. NetApp’s approach? It’s hard to decipher what it would mean to “move data in real-time, rather than retroactively.” Does that mean that data is moved when it’s written and then never moved again? That doesn’t sound better. My guess is that NetApp’s approach is very much like Compellent’s — something they should be touting rather than parrying. And I’d love to read that article.

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