5.005: who said it couldn't be done?
They said "it" couldn't be done. They said nobody else's array could do "it" – that only their array architecture could handle "it." They said all kinds of things about how "it" was going to bring the demise of Symmetrix, because Symmetrix would never do "it." Even if we could do “it,” they said we wouldn’t – but they said we can’t.
But they were wrong. VERY wrong.
Today EMC announced "it" is now available on VMAX. And then EMC went one better than they ever imagined – EMC took "it" further than they have been able to, even after all the (8+) years they have been shipping "it."
And of course, they will try to undermine the fact that they now have DIRECT competition from another array vendor who has implemented "it" - highlighting the history of EMC bashing "it", as if that matters any more. As I have noted before, being "first" is only important until there is a second - then all that matters is which implementation is better. And so they will childishly act like first means best perpetually.
Have you guess what "it" is yet?
More importantly, do you know who “they” are?
Read on to see what they never expected…and should have feared...
Yup. THOSE guys tried to convince users that EMC would never implement what they call “array-based virtualization.” They made crazy videos featuring zombies and even Mr. T in their lame attempts to discredit EMC’s network-based virtualization approach instead of “it.” Humorous though they may have been, word is that these marketing shenanigans ultimately led to the replacement of at least one generation of their marketing organization.
But the news this week isn’t simply that EMC has introduced array-based VMAX Federated Tiered Storage (a descriptive name we prefer over simple “storage virtualization” for reasons I will explain in this post).
No, the news is that we’ve upped the ante on what it means to leverage external capacity “behind” an array, in several key ways:
- Federated Tiered Storage (FTS) is implemented as a native data service of Enginuity 5876, and is provided to customers to support basic I/O to external capacity at no extra charge. Licensed features like FAST VP, SRDF, TimeFinder (etc.) will include external capacity as if it were internal Nearline drives – that is, the license charge will be for only 50% of the external capacity. But if you just want to VLUN existing LUNs into VMAX, no additional licenses are required. None. Nada. Zip. (And this is true no matter who the vendor of the external storage).
- FTS Implements proactive data integrity validation for all data written to external arrays, so as to protect against possible silent data corruption within them. This is a feature that, to my knowledge, nobody else provides today.
- FTS adds significantly less than 1ms of latency to most I/O operations directed to external capacity. This averages around 0.5ms or so, depending upon request size and workload. Competitive solutions add 1ms of latency or more…once again demonstrating the superiority of the Symmetrix VMAX architecture.
- Unlike the other guys’ so-called “universal” storage virtualization, FTS is specifically designed to utilize external capacity as a tier within FAST VP – they strongly recommend against using external storage with their automated tiering.
- Also unlike the competitors, FTS does not require external arrays to present “Windows” personality LUNs only – the VMAX implementation is far more robust and agile, able to encapsulate pretty much any LUN personality currently in use.
And finally, while VMAX FTS has not yet been qualified with as many external arrays as they currently support, EMC innovation is already at work. EMC is encouraging users to self verify FTS interoperability with their external arrays and to submit the results to EMC’s eLab for ratification. The expectation is that FTS will “just work” with most storage – the product has been architected around common FC personality models. Working with our users, we expect to round out the support matrix quite rapidly over the coming months.
silent data corruption
Of this list of differentiated features, I assert that item #2 above is the most important.
Long the Prime Objective of Symmetrix, Data Integrity should never be taken for granted. This is why EMC implemented a more robust variant of T10DIF in the VMAX – to verify that the data blocks we get back from a disk or flash drive have not gotten corrupted (the VMAX DIF also verifies that the block actually comes from the specified location (LBA)).
As I have noted before, silent data corruption is a reality of modern disk drives that most people aren’t aware of. It can happen on any drive, at any time, and unless the array implements checks and validations, these drive errors can be passed on to applications totally without notice.
So, for FTS, VMAX calculates CRC checksums for the data blocks that we write, and we keep them with the global metadata maintained within the VMAX. Although we do not write additional bytes to the external array, the checksum implementation can detect a huge percentage of what would be otherwise overlooked errors. If the data read is bad, FTS will attempt to reread the data multiple times before returning the standard SCSI error code for a failed read.
Now, they have been known to argue that the FC spec includes a per-frame CRC that does the same thing, but that’s misleading. The FC frame CRC does in fact ensure that the data received from the source is in fact unmodified in transit. But if the drive returns bad data to the array and it goes undetected by the array, the FC frame CRC will serve to ensure that the bad data is still bad…it cannot correct for silent data corruption if it happens before it is transmitted.
why federated, and not virtualized?
“Storage Virtualization” is a very general term. Taken literally, it simply describes what is the foundation of all storage arrays – take the various storage components controlled by the array(disks, DRAM, NAND, etc.), and present them to hosts as LUNs that behave as if they were in fact real, physical SCSI drives. This is pretty much what EMC invented over 23 years ago with its first external storage array.
So, rather than co-opt the term for yet another variation of “storage component” (i.e., external arrays), EMC chose to name the feature descriptively. Federated Tiered Storage is what you get when you put storage arrays behind a VMAX. “Federated” because the arrays now are working together to support the storage needs of the hosts and “Tiered” because the external storage has different operational, performance and reliability characteristics from the internal storage – which is pretty much how the Flash SSD, Enterprise HDD and Nearline HDD are differentiated within the array.
This notion of Federation – the cooperation and aggregation of disparate resources towards a common objective (from the BG dictionary ) – this is the foundation of how EMC is tackling the demands of the hybrid cloud.
FTS joins Federated Live Migration (FLM), a feature introduced last year to enable seamless and non-disruptive migrations of LUNs during Symmetrix-to-Symmetrix tech refreshes. Prior to the introduction of FLM, they would try to position storage virtualization as the only non-disruptive answer to tech refresh – when in fact, it still requires a disruption to insert the virtualization layer in between the hosts and the “old” storage…not to mention the fact that an outage is also required to tech refresh their array-based virtualization implementation.
Fact is, FLM is currently a Symmetrix-to-Symmetrix solution; FTS may thus be attractive to some for heterogeneous environments, and it does in fact support non-disruptively moving LUNs between any arrays within the host VMAX’s domain of capacity. VPLEX is another solution that is non-disruptive after the initial insertion into the I/O stream.
Like FTS, VPLEX delivers far more than simple migrations. As the only solution that delivers a true high-availability active/active LUN presentation that remains HA through a site outage or failure. But more on that in another EMC World-week related post .
The immediate focus of FTS is not migrations, but to support the utilization of external storage as another tier under the control of VMAX. FTS can be a powerful component for improving both operational and capital efficiency in customer environments. Being able to standardize on the Symmetrix robust suite of industry-defining storage services is very attractive, especially given the tremendous improvements that have been made in simplicity and ease of use in the latest release of Enginuity 5876.
Oh, and there will be more value-add build upon the foundation of FTS coming in the future.
I just can’t talk about that quite yet.
Admittedly, FTS represents an expansion of the approach EMC took to integrating storage resources before. I think of it as transformational – an evolution of strategy towards a much broader objective than simple migration challenges. In fact, FLM and FTS present two of the first steps towards the seamless federation of storage assets into a coherent, scalable, distributed and manageable pool of information storage resources. We at EMC see this notion of federation to be the requisite foundation the hybrid cloud.
In closing, I must admit that my persona (the storage anarchist) has long argued against the very notion of storage virtualization. In retrospect, I disagreed mostly with the limited focus (migrations) and the lack of data integrity in most everyone’s implementation. FTS addresses these concerns and expands the use cases, so I now have to admit…
…I have been transformed.