Most people know hard disk drives (HDD) as the form of data storage that uses mechanical parts rather than a solid-state drive that utilizes flash memory. What people may not know is that there are different forms of magnetic recording that take place within the hard drive. Both conventional magnetic recording (CMR) and shingled magnetic recording (SMR) are technologies used to physically store data on an HDD.
While there are benefits to each, Western Digital made the mistake of not telling customers which technology was used in their HDD, causing RAID failures. Drive manufacturers must ensure customers understand which type of hard drive technology is used so they can determine what will work best for their storage needs and device configuration.
Breaking Down CMR and SMR
CMR aligns poles of the magnetic elements perpendicularly to the surface of the disk in the hard drive. The magnetic elements in this technology represent bits of data. The magnetic tracks are written side-by-side and do not overlap. In general, the write head is larger than the read head, so manufacturers attempt to make the write head smaller in production.
SMR offers great areal density, which is how many bots of data can be recorded onto a magnetic disk. This technology overlaps each new track with part of the previously written track. That is why it is referred to as “shingled” technology because the recording is done like adding shingles to a roof. As the tracks overlap, the write heads become thinner and the areal density increases.
There are a few differences in each of these types of technologies and choosing the right one depends on what your individual use case is. The biggest difference is in the writing abilities of each technology. The CMR is the more common type of recording in hard drives today. The SMR, on the other hand, has a unique writing process. New data that is written will be added to an empty area on the disk while the file that would normally be re-written remains on the drive temporarily.
When the HDD is not being used for reading or writing, it will play a game of “catchup” where the old bits of data will be erased and there will be more room for new data to be written. This process can take time and only takes place when a hard drive is idle, making it ideal for archiving rather than constant use in a RAID. This is the issue that some users had with their Western Digital drives.
Western Digital Releases the Truth
Earlier this month, it was discovered that Western Digital, Toshiba, and Samsung were all shipping hard drives that used SMR technology in their product lines but did not tell the customers. Due to the extensive writing process for SMRs, those who purchased a drive from WD’s “Red Line” were experiencing difficulties when implementing the drive into their RAID array. In some cases, a RAID controller may refuse to repair the array of an SMR drive is used instead of a CMR.
In WD’s red product line, SMR technology was used in drives between 2TB and 6TB while the blue line had SMR in drives ranging from 1TB to 6TB. Finally, their black product line was using SMR in their 1TB drives. While SMR technology is cheaper, it also has lower performance for those who read and write files regularly, like consumers with RAID systems. WD addressed the issue by including a table on their website of what technology is used in which drives, so people know what they are buying.
Data Recovery for All Hard Drives
When it comes to buying a hard disk drive, the recording technology inside needs to match your needs as a tech user. No matter what type of drive you choose, there is always a chance for device failure. That’s why Secure Data Recovery is available with 24/7 customer support.
Our engineers have decades of experience recovering data from all makes and models of hard drive. The Research and Development team continues to find new recovery methods for existing media and devices that may soon come to market. We have an overall 96% rate in retrieving files from failed hard drives in PCs, laptops, Macs, and RAIDS. Call to start your case today at 800-388-1266.
