Having sat through numerous recent briefings about the relative benefits of fast storage, facts have been plentiful. This is about semiconductor based storage. In the following, I refer to this as SSD even though some implementations are not strictly speaking adhering to the SSD definition.

SSD Based Innovation

Those pesky old-fashioned spinning HDDs have the temerity to slow down transfer speeds due to seek and latency and the connection to the CPU. Fortunately, the IT industry is buzzing with vendors who can do transfers much faster than HDDs and much faster than their competitors’ SSD. The ingenuity in presenting servers with data on SSD is impressive:

  • on the server PCI bus
  • as a cache in the array
  • as tiers in the array
  • replacing entire arrays

But despite some of the convoluted claims I heard, HDD capacity remains cheaper than SSD. And the maximum possible number of flash based writes are limited. Then there are a list of technical issues such as wear levelling, write amplification, write cliffs etc.

These are generally common to all providers although there are ways of limiting the impact of those fundamentally inhibiting factors.

SSD is Not a Fad

However SSD is here for good. By injecting new layers or tampering with the existing layers of what used to be called the storage hierarchy (lots of cheap storage at the bottom, limiting the most expensive (fastest) storage at the top). A cynic might say that this serves as another reason for IT vendors selling more storage hardware to the IT data centres. But this spending is justified when it delivers true value. The extreme example is where IT latency is unacceptable to financial trading companies. The rest of the IT world needs to quantify just how valuable their various workloads are and add SSD where it is justified.

There is loads of exploring to do for IT professionals due to the many competing visions for SSD. This week EMC announced VFCache which interestingly goes outside EMC’s traditional storage realm, by putting flash in the server layer. As in the list of bullets above there are benefits to be reaped by each of the philosophies mentioned. Giving production environments the right performance edge at the right price is best explored by trialing the SSD philosophy that pass on to the customer shortlist.

Afterthought

The HDDs evolved into pretty impressive storage devices at affordable prices; or would someone beg to differ?