For many years traditional storage array vendors have claimed that their platforms are superior for block storage than NetApp FAS because they do not have the overhead of a Pointer-based Architecture – let’s explore this in more detail:
What do we mean by “pure” block storage?
Uses a Fixed Block Architecture whereby data is always read from and written to a fixed location (i.e. each block has its own Logical Block Address) – in reality most block storage arrays provide the option to use pages (ranging from 5 MB to 1 GB) where the LBA is fixed within the page, but the page can be moved to facilitate tiering.
The advantages of this architecture are:
The disadvantages of this architecture are:
How does NetApp FAS compare?
FAS uses a Pointer-based Architecture, utilising 4K blocks which can be located anywhere, called WAFL therefore we have to reverse the above list of advantages and disadvantages. NAS based file systems are delivered along with block storage on top of WAFL – block protocols do not sit on top of the NAS protocols instead they interact directly with WAFL.
The good news is that WAFL has been around since 1993 so it is a very mature and highly optimised technology – retrofitting advanced data services to a “pure” block storage array is not straight forward and requires major re-engineering work.
So which is best?
Well we can debate this endlessly and clearly depending on your use case one may be a better choice than the other – 5 years ago this was a valid debate, but to be honest it is a moot point as today all storage platforms have to support the advanced data services listed above and therefore need a Pointer-based rather than Fixed Block Architecture.
Let’s explore some examples of this:
It is also worth pointing out that all of the start-up storage vendors that have come onto the market in the last 5 years do not have “pure” block storage platforms – it would just not make sense if they did.
What is interesting is that NetApp do have a “pure” block storage array – the E-Series which provides excellent price/performance, but it lacks the advanced data services enabled by WAFL – also VVOLs support is not expected for some time.
So for me “pure” block storage is no longer sustainable and dismissing products like NetApp FAS because they are not “pure” block no longer makes sense. Moving forward the issue is not that your storage platform has a ground-up all-flash design, but does it have a ground-up Pointer-based Architecture.
“Pure” block storage is dead – long live WAFL and the like.