Subject: Storage, Shows and Expos | September 9, 2014 - 04:51 PM | Allyn Malventano
Tagged: WDC< Western Digital, WD, idf 2014, idf, hdd, Cold, Archival, Ae
We talked about helium filled, shingled HDD's from HGST earlier today. Helium may give you reduced power demands, but at the added expensive of hermetically sealed enclosures over conventional HDD's. Shingling may give added capacity, but at the expense of being forced into specific writing methods. Now we know Western Digital's angle into archival / cold storage:
..so instead of going with higher cost newer technologies, WD is taking their consumer products and making them more robust. They are also getting rid of the conventional thinking of capacity increments and are moving to 100GB increments. The idea is that once a large company or distributor has qualified a specific HDD model on their hardware, that model will stick around for a while, but be continued at an increased capacity as platter density yields increase over time. WD has also told me that capacities may even be mixed an matched within a 20-box of drives, so long as the average capacity matches the box label. This works in the field of archival / cold storage for a few reasons:
- Archival storage systems generally do not use conventional RAID (where an entire array of matching capacity disks are spinning simultaneously). Drives are spun up and written to individually, or spun up individually to service the occasional read request. This saves power overall, and it also means the individual drives can vary in capacity with no ill effects.
- Allowing for variable capacity binning helps WD ship more usable platters/drives overall (i.e. not rejecting drives that can't meet 6TB). This should drive overall costs down.
- Increasing capacity by only a few hundred GB per drive turns into *huge* differences in cost when you scale that difference up to the number of drives you would need to handle a very large total capacity (i.e. Exabytes).
So the idea here is that WD is choosing to stick with what they do best, which they can potentially do for even cheaper than their consumer products. That said, this is really meant for enterprise use and not as a way for a home power user to save a few bucks on a half-dozen drives for their home NAS. You really need an infrastructure in place that can handle variable capacity drives seamlessly. While these drives do not employ SMR to get greater capacity, that may work out as a bonus, as writes can be performed in a way that all systems are currently compatible with (even though I suspect they will be tuned more for sequential write workloads).
Here's an illustration of this difference:
The 'old' method meant that drives on the left half of the above bell curve would have to be sold as 5TB units.
With the 'new' method, drives can be sold based on a spec closer to their actual capacity yield. For a given model, shipping capacities would increase as time goes on (top to bottom of the above graphic).
To further clarify what is meant by the term 'cold storage' - the data itself is cold, as in rarely if ever accessed:
Examples of this would be Facebook posts / images from months or years ago. That data may be rarely touched, but it needs to be accessible enough to be browsed to via the internet. The few second archival HDD spinup can handle this sort of thing, while a tape system would take far too long and would likely timeout that data request.