Huawei’s in-house development of Magneto-Electric Disk (MED) archive storage technology combines an SSD with a Huawei-developed tape drive to provide warm (nearline) and cold data storage.
MED technology was first revealed back in March. We were told that, facing potential disk supply disruption due to US technology export restrictions, Huawei was working on its own warm and cold data storage device by combining an SSD, tape cartridge, and drive in a single enclosure. Its storage portfolio could then run from fast (SSD) for hot data and MED for warm and cold data, skipping disk drives entirely.
Presentation images of the MED now show a seven-inch device:
The MED is a sealed unit presenting a disk-like, block storage interface to the outside world, not a streaming tape interface. Inside the enclosure there are two separate storage media devices: a solid-state drive with NAND, and a tape system, including a tape motor for moving the tape ribbon, a read-write head, and tape spools.
This is unlike current tape cartridges, which contain a single reel of tape, approximately 1,000 meters long, and have to be loaded into a separate drive for the tape to be read and have data written to it. A tape autoloader contains the motor and spare reel with tape cartridges loaded into it and moved to the drive by a robotic mover. Much bigger tape libraries also have robotics to select cartridges from the hundreds or thousands stored inside them, and transport them to and from the tape drives.
The MED contains an internal motor to move the tape and an empty reel on which to rewind the tape from the full reel after it is pulled out and moved through the read and write heads. A conceptual diagram of the device illustrates its design:
The MED contains a full reel of tape, about half the length of an LTO tape, motor, read-write heads and an empty reel to hold the used tape. Huawei engineers could choose to have the tape ribbon positioned by default with half on one reel and half on the other so that the read-write heads are at the midpoint of the ribbon, shortening the time to get to either end of the tape.
The system is designed to be a combined archive for cold data and nearline store for warm data. Data flows into the MED through the SSD at NAND speed, from where it is written to the tape in sequentially streamed blocks. Warm data can be read from the SSD at NAND speed. Cold data is read from the MED more slowly as it has to be located on the tape and the tape ribbon moved to the right position before reading can begin. This can take up to two minutes.
The MED has a disk-like, block interface, with the SSD logically having a flash translation layer (FTL) in its controller that takes in incoming data and stores it in NAND cell blocks. From there, a logical second tape translation layer assembles them into a sequential stream and writes them to the tape.
When the MED receives a data read request, the controller system locates the requisite blocks using a metadata map, stored and maintained in the NAND, and then fetches the data either from the NAND, or from the tape, streaming it out through the MED’s IO ports.
Huawei and its Chinese suppliers have developed their tape media and the read-write technology, not using IBM LTO tape drive technology or LTO tape media, which is made by Fujifilm and Sony. The tape media ribbon is about half the length of an LTO tape and has a much higher areal density. The MED NAND is produced in China as well. Huawei is open to using NAND from other suppliers should US technology export restrictions allow it.
The MED system and its components are protected by patents. The first-generation MED should arrive sometime in 2025. A second-generation MED, with a 3.5-inch disk bay slot size, with a shorter and much higher density tape ribbon, has a 2026/2027 position on the MED roadmap:
- A gen 1 MED will store 72 TB, and draw just 10 percent of the electricity needed by a disk drive.
- It should have a 20 percent lower total cost of ownership than an equivalent capacity tape system.
- A gen 1 MED rack will deliver 8 GBps, hold more than 10 PB, and need less than 2 kW of electricity
- We don’t know if the 72 TB capacity is based on raw or compressed data.
The MEDs won’t run hot as they store mostly archive data. A MED chassis has no need of robots and can be filled with MEDs like a dense JBOD. It will function like a better-than-tape archive system, providing much faster data access, both for reads and writes, draw less electricity, and occupy less datacenter rack space.
It is simple to envisage MED variants with more or less NAND storage, pitched at applications needing more or warm storage compared to cold, archival data storage in the future, squeezing the disk market somewhat. In effect, Huawei is compressing the storage hierarchy from three elements to two. From “SSD-to-HDD-to-Tape” to “SSD-to-MED.”
Such two-element hierarchies could be easier to manage, more power efficient and enable faster cold data access. They could become popular in regions with constrained disk supply through US restrictions, and elsewhere as well, because they will make on-premises datacenter and tier 1, 2, and 3 public cloud archival storage more practicable. Chinese public cloud suppliers are having conversations with Huawei about using the technology, we’re told.
It is possible that MEDs could have a profound effect on the robotics-using tape autoloader and library systems markets, prompting suppliers of such systems to look at developing their own MED-like technology. MEDs might also add to the pressure on disk drives from NAND by moving some nearline data to MEDs, squeezing the disk drive market from two sides.
It’s notable that Huawei has only developed its MED technology because of US disk tech export restrictions, and that MED technology could end up threatening Western Digital and Seagate because of Huawei’s inventive response to those restrictions.
Bootnote
Huawei is said to be developing its own 60 TB capacity SSD, using QLC NAND with an SLC cache.
