Hu Yoshida, CTO of Hitachi Data Systems and long time legend of the storage industry is a person I respect a lot. Hu and I recently engaged in a discussion around the validity of architectures like VSP and their designation as Tier 1, which Hu summarised in a recent blog post he
cut and pasted wrote. Hu has asked that I summarise my thoughts on the topic in a blog post so that he can fully digest and potentially answer. Here goes.
NOTE: Although the discussion Hu and I had was over Twitter, I should point out that I have met Hu many times in person and he is an absolute legend and despite being over 70 years old would kick my rear in a fist fight!
Tier 1 Shmear 1 Zzzzzzzz
We’ve been here a million times before and I wont drag it out. Although there is no strict definition of what Tier 1 is, most people have a good idea…. usually VMAX, VSP (and P9500 OEM’d by HP) and occasionally DS8x00 from IBM. Enough on that.
My point is that traditional definitions of Tier 1, and hence the platforms that cling to this accolade, are becoming less and less relevant by the day. And the reason is clear….. SSD!
SSD Has Changed Everything
Before the rise of SSD, it was accepted that Tier 1 storage sucked in performance compared to RAM in a server, often by several orders of magnitude. Those were hideous days!
Fortunately those days are drawing to an end. Application owners, and even some business folks, are becoming savvy to the delights of SSD. The cat is out o the bag so to speak, the horse has bolted. And once the horse has bolted there is no reigning it back. Beleive me this is a good thing!
While I’m a fan of much of the architecture behind VMAX and VSP (especially VSP/P9500 as I’m a sucker for customised designs) there is no getting away from the fact that the way VSP/P9500 and VMAX implement SSD is a bit of a fudge. They have basically lashed 3.5-inch and 2.5-inch SSD drives onto their existing back-ends. Back ends that were designed for rotating rust, not SSD.
And its not just back ends, these so called intelligent controllers have been designed and honed over the years for spinning media, again, not SSD. What am I saying….?
Well…Take the spec sheet numbers for a ZeusIOPS SSD from STEC. We’re talking 120,000 read IOPS and 75,000 write IOPS. Say what you will about vendor spec sheet numbers, these are crazy figures compared to 15K FC/SAS spinning disk.
The question then begs…. how many of these bad-boys can a traditional controller architecture like VSP/P9500 or VMAX drive across its back end? Let me cut the suspense, not many! In fact I might challenge whether a VSP/P9500 or VMAX can even drive a single one of these drives across its back end! Correct me if I’m wrong, but I wont be holding my breath for a corrective response.
And of course, none of the above stops any of the vendors from selling them to you, at a cracking price too.
Do They Need to be Driven?
While I appreciate that there is some foundation for a counter argument that traditional controllers do not necessarily need to drive SSD hard due to auto-tiering technologies such as FAST VP, Hitachi Dynamic Provisioning/HP Smart Tiers. However, then why not sell something more suited to the controller and back end architecture. Say something more like Mach16, Mach8IOPS etc also from STEC. They seem cheaper and more suited toward the specks of traditional T1 controllers.
So What’s the Answer
I’m certainly not a planet sized brain guy that works for a vendor, but I’ve seen some stuff that looks like it will fit the bill nicely….
Technologies such as SCSI Express and NVM Express look like cracking candidates. Technologies/protocols designed especially for SSD.
Keep the SSD closer to the controller.
There is absolutely place for SSD in the server, but also in the shared storage array… just not hidden away on the back end loop of a shared storage array like some unwanted child.
Keep it closer to the controller where it can be accessed faster and driven better. From here it can be used as a 2nd level cache (as in FAST Cache, only not starved on a back end loop like existing FAST Cache implementations) or as a LUN or extent of a LUN, as in FAST VP or HDP/Smart Tiers.
Hell ,we wouldn’t dream of exiling VSP or VMAX DRAM on a back end loop. Why do the same with SSD!?
Sure I appreciate that it was done as a quick fix, “get SSD in their no matter how you do it”, and disk drive form factor on a back end loop was the simplest and path of least resistance. But it’s ugly!
Todays Gen1 Implementations Are Not All Bad
While I admit that todays SSD implementations in VSP/P9500 and VMAX do serve some customer requirements. They do not do it very efficiently. And I also admit that the vendors have done some work to smooth the road to SSD in their existing T1 architectures such as tuning caching algorithms and making sure that SSD access doesn’t hog the loop (pun intended).
However, existing implementations are somewhat like driving a Ferrari around central London. Build a freeway!
If things don’t get better, the rising generation of arrays bearing the mark “Designed for SSD” such as WhipTail, Kaminario, Violin Memory etc will start to crop up in traditional Tier 1 accounts. These guys are working hard at implementing many of the traditional Tier 1 features into their products, features like NDU code upgrades, replication…. oh and cloud integration.
Yes, Tier 1 is about robust replication, caching, N+1 or higher…. but its also about performance. High performance storage is still a bit nichey today, but it wont be tomorrow. Oh and it’s getting late!
UPDATE: (3rd April 2012) It seems I need to add a clarification to this post.
I am absolutely not saying that performance is the numero uno characteristic of Tier 1 storage systems. What I am saying is it is one characteristic. No high performance, no Tier 1 badge.
My point being that the rise of SSD is redefining everybody's performance expectations – massively. To the point where if the traditional Tier 1 vendors dont keep pace, they will no longer be considered performant. No high performance, no Tier 1 badge.
Also. Im not saying the current crop of SSD vendors are better than the current crop of Tier 1 vendors. I am saying that the current crop of SSD vendors are disrupting the industry and that disruption will only increase as each day passes. The current crop of tier 1 guys need to up the ante or risk becoming dinosaurs of the industry.
Oh and Im not bashing Hitachi or EMC, hopefully that came across early on in the post when I stated that Im a fan of the architectures, especially VSP/P9500