I come not to praise the traditional legacy storage array (TLA), but to bury it. The architectural model that served it so well for so long, has reached the end of it’s useful lifespan. Killed ironically by the technology that it thought would prolong it, Flash.
Sadly for many customers, the end of the TLA will be more like a long slow death spiral, rather than an abrupt demise. Sad because those customers will spend money and time trying to make the wrong architecture work.
Why?
The traditional storage array is optimized for read operations. The array minimizes the amount of effort it has to do on a read by putting the disk block exactly where the client thinks it is. This means on a read, the array has to do a trivial lookup to get the disk block.
However, the downside is that the array makes the write operations more expensive.
When you factor in RAID and the impact of RAID on write performance, the TLA offers a poor value proposition.
But the poor write performance was okay as long as the read operations dominated.
Enter bigger memories
The problem with the TLA architecture was that it was designed in a pre-64 bit era, and in a pre-flash era. In that era, the servers connected to the storage array were memory starved. Because they were memory starved, the buffer cache on the server was quite small, resulting in more IO operations for reads.
In the new 64 bit era, and especially with the availability of Flash, the servers are no longer memory starved. You can now have more volatile memory than you ever had before. What that means is that the average server is rarely doing a read operation, but instead is mostly doing write operations.
The impact on the TLA is that the workload shifts from being dominated by read operations to a bigger mix of write operations.
The problem, then, is that the poorly optimized path is now a bigger piece of the overall workload mix.
Or more to the point, that poor write behavior around RAID-6, suddenly becomes a very big issue.
Which is why, after all, the TLA vendor is recommending RAID-10.
Their poor write performance is forcing them to throw more hardware at the problem.
And their poor write performance is forcing application administrators to look at alternative storage architectures.
Enter write optimized storage arrays
Write optimized storage arrays, like ONTAP, are designed for this new world order. The downside, of course, is that the read operations are more expensive, but if the mix shifts between read and write, then that’s a reasonable tradeoff.
And as I’ve said before you can solve the read performance problem …
And why do I pick this date?
Because it has been almost a year and a half since the time the Better Than Real Fibre Channel guys demonstrated that their architecture outperformed the TLA.
An architecture optimized for read was beaten by an architecture optimized for writes, and the response continues to be silence.
So goodbye TLA, you are so last decade…
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