cross-posted from: https://beehaw.org/post/24650125
Because nothing says “fun” quite like having to restore a RAID that just saw 140TB fail.
Western Digital this week outlined its near-term and mid-term plans to increase hard drive capacities to around 60TB and beyond with optimizations that significantly increase HDD performance for the AI and cloud era. In addition, the company outlined its longer-term vision for hard disk drives’ evolution that includes a new laser technology for heat-assisted magnetic recording (HAMR), new platters with higher areal density, and HDD assemblies with up to 14 platters. As a result, WD will be able to offer drives beyond 140 TB in the 2030s.
Western Digital plans to volume produce its inaugural commercial hard drives featuring HAMR technology next year, with capacities rising from 40TB (CMR) or 44TB (SMR) in late 2026, with production ramping in 2027. These drives will use the company’s proven 11-platter platform with high-density media as well as HAMR heads with edge-emitting lasers that heat iron-platinum alloy (FePt) on top of platters to its Curie temperature — the point at which its magnetic properties change — and reducing its magnetic coercivity before writing data.
Question: Are failures due to issues on a specific platter? Meaning, could a ZRAID theoretically use specific platters as a way to replicate data and not require 140TB of resilvering on a failure?
@Fmstrat @veeesix Since there’s two very diffrent questions there… The first, “where do the failures happen?”: anywhere. It could be the controller dying (in which case the platters themselves are fine if you replace the board, but otherwise the whole thing is toast). It could be the head breaking. It could be issues with a specific platter. It could be something that affects _all_ the platters (like dust getting inside the sealed area). So basically, it very much depends.
@Fmstrat @veeesix The second, could you do raid across specific platters - yes and no. The drive firmware specifically hides the details of the underlying platter layout. But if you targeted a specific model, you could probably hack something together that would do raid across the platters. But given the answer to the first question, why would you?
Great answers, thank you.
IIRC, HDDs have some reserved sectors in case some go bad. But in practice, once you start having faulty sectors it’s usually a sign that the drive is dying and you should replace it ASAP.
I think if you know drive topology you can technically create partitions on platter level, but I don’t really see a reason why you’d do it. If the drive is dying you need to resilver the entire drive’s content to a new disk anyway.