Western Digital Release 22TB Hard Drive in WD Red Pro, WD Gold and WD Purple
That’s Right! WD has now officially released their 22TB series of HDDs to the WD Gold, WD Red Pro and WD Purple Pro series of hard disks. So, why is this such a big deal? Well, anyone who has been watching the development of hard drives over at Western Digital will have surely noticed a tremendous change in strategy by one of (if not THE) biggest brand in hard drives in the last couple of years. For a long time, WD had been a little more cautious in it’s releasing of larger capacities (especially compared with their biggest rival Seagate) and was rarely the first to commercially release the biggest capacities into the consumer and business market. However, the last 24 months have seen WD change this development/release method dramatically and we have seen them release a wide variety of extremely high capacity HDDs into their respect ranges (we only JUST reviewed their 20TB WD Red Pro on YouTube and Western Digital Ultrastar HC560 20TB HDDs here on NASCompares shortly after release). Add to this that these larger capacity HDDs are getting added to each of the brand’s highest-profile product ranges (as well as the 26TB Ultrastar UltraSMR drives being released now in July ’22) and we are seeing a very, VERY different WD to one we saw back in 2019/2020. So, let’s take a closer look at these three new 22TB Hard Drives, what they are designed for and what separates them from one another!
Hardware Specifications of the WD Red Pro, WD Purple and WD Gold 22TB Hard Drives
The first thing to note is that these three 22TB hard drives is that they are designed very similarity in terms of standard hardware architecture. They are all 7200 RPM (rotations per min) and data is spread across 10 internal platters that are comprised of 2.2TB per platter. Despite it’s remarkable capacity, the drive uses traditional CMR/PMR, but is improved upon with the use of energy-assisted magnetic recording too. These amply internal physical storage spacing in accompanied with a huge 512MB of on board cache to keep things moving and each drive also features a small flash module on board known as OptiNAND (we will go into more detail on that in a moment). All three 2TB Hard drives are available in SATA/6Gb (and SAS options available in other model IDs), but thanks to small differences in the gearing of each drive to be better suited to their end user, the WD Red Pro and WD Purple Pro have a maximum reported 265MB/s Sustained Sequential Read and the WD Gold has a much higher and possibly industry winning (for SATA in traditional platter-arm design) 291MB/s Performance, almost half way saturating SATA 6Gb/s. Herre is a breakdown of the specifications of each of the WD 22TB Hard Disks:
|Drive Family||GOLD||RED PRO||PURPLE PRO / AI|
|Price||£639.99 / $769 (Est on Conversion)||£601.99 / $729 (Est on Conversion)||£539.99 / $649 (Est on Conversion)|
|Designed Use||Data-Center||Large Scale NAS||NAS Surveillance / NVR|
|RPM (Rotations per Minute)||7200RPM||7200RPM||7200RPM|
|Platter Density/Frequency||10 Platters (2.2TB each)||10 Platters (2.2TB each)||10 Platters (2.2TB each)|
|Max Performance (aka Transfer||291||265||265|
|Workload Rating (TB per Year)||550||300||550|
|Load / Unload Cycle Rtaing||600K||600K||600K|
|Unrecoverable Read Errors||1 in 10E15||1 in 10E13||1 in 10E15|
|MTBF (Mean Time Between Failure Hrs)||2.5M||1M||2.5M|
|Power Usage (Idle / Active) (W)||5.7 / 9.3||3.4 / 6.8||5.6 / 6.9|
What is the Difference Between the 22TB WD Red Pro vs WD Gold vs WD Purple Pro HDD?
The WD Red Pro series of HDDs are designed for use in 24×7 NAS servers that are used in Medium-large businesses (recommended for any system in desktop or rackmount above 8 bays). The WD Gold series is designed for Enterprise, Data Center and/or Hyper-scale deployment, as they are geared towards a much faster spin up and spin down, whilst also ensuring high sustained speeds over time and can endure larger scales of write-delete-re-write throughout their lifespan (something very common in enterprise hot-warm-cold storage systems that use different media types at each tier). Finally, there is the WD Purple Por series, a range of drives specifically geared towards surveillance (cameras and data recording instruments generally) and although similar in deployment to the WD Red Pro series (ie small-medium-large business and above 8 bays of storage per system), the main difference is that WD Purple is significant;y geared more towards Write than read, as NVR/Surveillance-servers will spend 95%+ of there operations time WRITING data from recording cameras etc , whilst 5% or less will be spent retrieving/viewing those recordings.
The main difference between all three in terms of actual use is:
- The WD Purple 22TB is an HDD that will allow a tremendously sustainable Write Speed over time but not at the expense of durability, thanks to a high 2.5M MTBF and 550TB annual workload. Therefore ensuring that surveillance recordings are consistent and the drive will have sufficient robust hardware to endure repeated write actions over and over. That heavier focus on write-over-read results in the drive arriving noticeably lower in price than the WD Red Pro or WD Gold.
- The WD Red Pro 22TB HDD on the other hand has a much better Read/Write balance and although is not quite as high in it’s durability upon repeated/recycled writing, it makes up for it by being much better than the Purple Pro when it comes to mixed and sporadic access patterns, as a 24×7 large scale NAS server is likely to do
- The WD Gold 22TB is the premium Hard Drive of the three, with it’s excellent sustained read AND write, as well as high durability of 550TB per year workload, 2.5M MTBF hours and it’s suitability of deployment in hyperscale (12-24-48+ bay) rack environments of NAS or SAN. The only real downside compared with WD Red Pro and WD Purple Pro is that the drive is noisier and consumes more power in use to maintain those speeds and durability over time. The price tag of the WD Gold (at least at the time of writing) is higher than the WD Red Pro and WD Purple Pro too – though that can change later as larger capacities arrive and the RRP becomes increasingly flexible.
That is the core difference between all three 22TB HDDs that WD have released. But what about OptiNAND? Why is that a big deal?
What is OptiNAND and Why is it so Important on a big drive like the WD 22TB?
Of course, users who have been following the developments of WD in their roadmaps and reveals of larger-scale drive media will be aware that the WD Red Pro, Purple and Gold 22TB also features a new technological design being rolled out in these bigger drives to merge existing storage technologies into something even better – OptiNAND. This is a new approach to an old idea that never really took off, where the benefits of small areas of faster NAND storage (more typically associated with SSD media) and affords a small area of NAND to a larger scale hard drive to be used for metadata and for storing data in the event of power failure. Flash is also interesting from a persistence standpoint. DRAM gets flushed on power loss, but NAND is non-volatile and can continue to keep metadata information without having to re-hydrate after a boot sequence, be removed from the system for some reason, or any other event where power drops. The newer gen 18, 20 and 22TB hard drives arrives with a portion of 64-layer/64GB BICS3 (3D TLC)
WD states that OptiNAND drives can secure more than 100MB of write cache data in the event of an unplanned power loss, a 50X improvement over standard drives that can flush about 2MB. Hybrid Drive media is not new, but whereas older generation hybrid drives were more parallel in architecture, this is far more intertwined. It also brings enhancements to the firmware algorithm and system-on-a-chip (SoC). Once again, to be clear, OptiNAND and its iNAND isn’t flash cache (such as the 512MB this drive also features). Rather, it’s a portion of flash memory used to store metadata–or data about existing data–so they can be managed more efficiently.
The slice of iNAND has its own dedicated controller, much like an SSD. While metadata management itself doesn’t help to increase platter density, it enables a range of benefits that do. As one can imagine, the higher the density of the HDD, the more metadata it generates. Moving metadata to a fast, dense and scalable storage area gives more freedom for manufacturers to create higher capacity drives.
But why choose NAND over DRAM? Western Digital explained back in August 2021 that modern high-density HDDs generate gigabytes of metadata and it’s too costly to include sufficient DRAM to hold it. In addition, moving metadata to their own dedicated area will free up more space on the platters themselves to store user data. There’s more to it than capacity increases, though; using OptiNAND also helps with reliability, specifically with the repeatable runout (RRO) and adjacent track interference (ATI).