Shingled Magnetic Recording

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Shingled Magnetic Recording with overlapping tracks

Shingled magnetic recording ( SMR ) ( English shingle : (roof) Schindel) is a technique for data storage on magnetic media , which in hard disk is used (HDDs) to the storage density and the total storage capacity of a drive in relation to the conventional recording method Perpendicular Recording (PMR, also known as Conventional Magnetic Recording CMR). Previous methods store data by creating separate magnetic trackswritten side by side; With shingled recording, on the other hand, a track is written in such a way that it overlaps part of the adjacent track, making the adjacent track thinner - this allows a higher track density. The overlap is similar to that of roof shingles , which is why the process is named. This procedural approach was chosen because physical restrictions prevent the electromagnetic write head of a hard disk from being as small as the read head - with shingled recording it can be larger.

Overlap propagation

Writing a track leaves a narrow but sufficient strip of the previous track, but overwrites the following track (s) so that the following track, if it contains data, must also be written again; so the need to refresh the data continues in the direction of the following lanes. In order to avoid that the entire SMR area of ​​the hard disk has to be renewed (from the point of change), a gap is provided at regular intervals, at which the overlap propagation stops.

Speed ​​and management

The necessary refreshing of neighboring tracks generally reduces the writing speed . Therefore, SMR hard drives have an area (mostly in the fast outer zone) that is written to in a non-overlapping manner and serves as a cache ; the data temporarily stored there are only transferred to the SMR area when there is a break. Hard disks that manage this SMR recording internally ( device-managed ) hide these complex processes and handle them themselves using their firmware  - they offer the same standard interface as all other common hard disks. In the case of ( host-managed ) SMR hard disks, on the other hand, the operating system or its device driver must act accordingly and may only write to a track if no existing subsequent data is affected.

distribution

Seagate has been supplying SMR hard drives since September 2013, for example the ST8000AS0003 drive (2018, 8 TB) designed for server applications . The first drives in 2013 achieved an increase in storage capacity of around 25% compared to hard drives with other storage methods. In September 2014, HGST announced a 10TB drive filled with helium that also uses Shingled Magnetic Recording.

In addition, research in specialist journals in April 2020 showed that all major manufacturers sell hard drives with SMR without marking it. Due to the reduced write performance and possible incompatibilities in the RAID network with other hard drives without SMR technology (the controller suspects a defect due to the low speed), the lack of identification has been criticized. In the following product series, the use of SMR could be verified without labeling:

  • Toshiba
    • DT02: 4 TB and 6 TB
    • P300: 4 TB and 6 TB
    • MQ04: 1 TB and 2 TB
    • L200: 1 TB and 2 TB
  • Western Digital
    • WD * 0EFAX: 2 TB, 3 TB, 4 TB and 6 TB
  • Seagate
    • Barracuda ST2000DM008 (2 TB)
    • Barracuda ST4000DM004 (4 TB)
    • Barracuda ST8000DM004 (8 TB)
    • Desktop HDD ST5000DM000 (5 TB)

Alternative developments

Other approaches to increasing the storage density of hard disks are, for example, (bit) patterned media or filling the hard disk with helium in order to allow the heads to be kept closer to the surface.

See also

Web links

Individual evidence

  1. ↑ a b Anand Lal Shimpi: Seagate to Ship 5TB HDD in 2014 using Shingled Magnetic Recording . AnandTech . September 9, 2013. Accessed February 9, 2015.
  2. ↑ Roger Wood: Shingled Magnetic Recording and Two-Dimensional Magnetic Recording (PDF) October 19, 2010. Retrieved December 14, 2014.
  3. ↑ What is Shingled Magnetic Recording (SMR)? . January 30, 2015. Accessed February 9, 2015.
  4. ^ A b Mary Dunn, Timothy Feldman: Shingled Magnetic Recording: Models, Standardization, and Applications (PDF) Storage Networking Industry Association . September 22, 2014. Accessed February 9, 2015.
  5. ↑ Seagate Support: Seagate's Shingle Magnetic Recording tears down capacity limits. . Retrieved July 14, 2019.
  6. ↑ Jake Edge: Support for shingled magnetic recording devices . LWN.net . March 26, 2014. Retrieved December 14, 2014.
  7. ↑ Datasheet: ST8000AS0003. Seagate, accessed November 8, 2018 .
  8. ↑ Geoff Gasior: Shingled platters breathe helium inside HGST's 10TB hard drive . In: The Tech Report , September 9, 2014. Retrieved February 9, 2015. 
  9. ↑ Lutz Labs: Specifications? No matter ... - NAS problems due to SMR hard drives in c't 11/2020, p. 146.
  10. ↑ Michael Günsch: WD Red: Some hard drives use SMR without identification. Retrieved April 18, 2020 .
  11. ↑ Michael Günsch: Hard drives: Seagate also has SMR as a surprise. Retrieved April 18, 2020 .
  12. ↑ Michael Günsch: Without exception: With Toshiba, all HDD manufacturers keep silent about SMR technology. Retrieved April 18, 2020 .