Update 5:08 pm ET: Prices
Ars asked a senior Western Digital executive about the prices of the new Red and Red Plus lines. The initial response was “overall we expect WD Red drives to be priced lower than WD Red Plus drives.” When asked to comment on how the prices of existing EFRX and EFAX models will change to make Red less expensive than Red Plus, the only response was “I can only comment on the [preceding] At this time, “followed by” WD Red Plus will be available in the August period. “
Original story 7:34 am ET
Last night, a Western Digital executive contacted Ars to inform us of a blog post about his controversial red impulses.
The company is taking a new branding initiative to clarify the technology used in its NAS drives: in the near future, “WD Red” will exclusively mean discs with Shingled Magnetic Recording technology and “WD Red Plus” will mean discs with conventional magnetic recording. .
This report is the latest in a series on hard drive manufacturers incorporating SMR technology into existing disk lines, with little or no notification to customers.
In summary (very), SMR disks generally perform well enough on light storage workloads, with a lot of downtime between storage requests, but they can catastrophically fall on their faces when faced with more demanding workloads. The ZFS file system, in particular, tends to present SMR disks with challenges that they have difficulty handling.
Although the three main remaining providers of hard drives: Western Digital, Toshiba and Seagate, have “underwater” SMR drives on existing channels without doing much to notify customers about it, only Western Digital has done so with drives designed specifically for NAS. o Network Storage attached, use.
Unfortunately for Western Digital, NAS users tend to be significantly more technical than consumers in general, and they often hit their drives with much more difficult workloads than Western Digital apparently tried or planned.
From red to red more
The use of SMR technology in Western Digital Red will not disappear, but in the future, “Red” will. exclusively medium SMR disks. Existing SMR models —WD 20/30/40/60 EFAX — will retain their existing model numbers and retain their existing WD Red brand. Meanwhile, CMR drives formerly known as WD Red, in sizes from 1TB to 14TB, get a new brand and label “WD Red Plus”, although their model numbers also remain the same.
Western Digital’s new marketing for SMR-equipped red disks labels them for SOHO use only and clarifies that this means low intensity operations with a lot of downtime in the media, and no ZFS. For small, “intensive” or ZFS workloads, there is the Red Plus line, which effectively only means the previous models, pre-SMR for now.
There is also a Red Pro line aimed at maximum performance applications. This line has not changed: it existed under the same brand before the SMR fiasco, and it still exists under the same brand and same models today.
Understand the limitations of SMR
There is a fairly large CMR cache area on SMR disks otherwise, as well as a 256MiB volatile cache (RAM). Western Digital does not publish details about the CMR cache area in its product data sheets, unfortunately, but typical estimates, such as what was shown in this block and file interview, range from 1GiB to 100GiB, depending in part on size. of the disk.
The CMR cache area on the disk will function in the same way as a full CMR disk, and if you have “downtime” between storage requests, the unit’s firmware may spend that time reading CMR cache data and greatly reducing it . Limited primary SMR storage area. Once permanently stored in SMR zones, data can be read at approximately the same speed as an equivalent CMR disk – SMR performance limitations are strictly tied to writes.
If you never committed enough write operations at once to overflow the large CMR cache area, and gave the disk a prolonged amount of downtime to “breathe”, you wouldn’t see any performance difference between CMR and SMR disks, though As some NAS users have commented, “You can hear them running all the time.” This refers to the garbage collection process that migrates CMR cache data to SMR zones that occur during long downtimes between operations.
Even if you commit enough large write operations at once to overwhelm the CMR cache, in our tests, Western Digital’s SMR firmware generally does a surprisingly good job of committing writes directly to SMR zones. However, this good work is based on the fact that these writes are large and contiguous writes, and that they are new writes, not rewrites of existing data. To modify a single 4KiB sector in a 256MiB SMR zone, the firmware must read over the entire 256MiB zone, then modify that sector, and then rewrite the entire 256MiB zone.
Is the new brand enough?
The new brand is certainly a big step forward for more informed consumers who already know they don’t want SMR: all they need to know is “Red” means SMR, and “Red Plus” and “Red Pro” mean CMR. The new brand replaces long tables filled with internal model numbers, which may not be accurately reflected on reseller sites, even if consumers know which ones to use.
However, we are not sure whether the easier new brand will satisfy the ongoing lawsuits against Western Digital. A US class action lawsuit alleges that marketing any SMR disc as “NAS” discs amounts to actionable false advertising. The new brand is a great help to consumers who already know what SMR means and what its limitations are, but it is unlikely that it will do much to educate consumers who are not yet aware.
Our use case analysis shows that SOHO workloads are generally based on short periods of drive access. This results in extremely low average throughput (compared to available disk performance) and provides plenty of downtime for the DMSMR disk to perform the necessary background operations, making it ideal for this application.
Broadly speaking, we agree with the above quote from the Western Digital blog post announcing the new brand. Most consumers who buy Synology, Netgear, or other specially designed small NAS devices are likely to use them on and off, with a small number of users overall, and primarily for large files like digital photos, movies, and music. For those consumers, an SMR-equipped Network will probably be fine: They are unlikely to go through the CMR cache, and even if they do, the SMR management firmware can probably handle direct writes quite well.
The real question to move forward is how well the Western Digital blog post announcing the new brand will tie in with the actual product details seen on reseller sites. If there isn’t a prominent disambiguation between Red, Red Plus, and Red Pro on the product pages, the new brand may not reach many of the people who need to see it.