How to tell a difference between DM-SMR and non-SMR (CMR) drives (HDD) – compare

Your story on WD using SMR in some drives without mentioning it on the spec sheets was eye opening. The WD representative’s wording about the suitability of SMR for archival purposes brings up the question of the WD “White” drives that are included in external USB storage offerings. There are many YouTube videos that recommend shucking these white label drives as a cost effective way to obtain “real WD RED drives” masquerading as a cheaper drive. Is it likely/possible that the white label drives are actually DM-SMR drives?

The easiest way to detect whether it is a SMR drive is the cache size. Old drives (WDx0EFRX) had 64MB cache whereas new replaced drives (WDx0EFAX) feature 256MB.  You can also read the serial number on the disk itself and compare it to a table bellow.

If you have existing RAID with old 2TB/3TB/4TB/6TB EFRX CMR drives and you need a replacement drive or you want to expand your RAID with an extra drive make sure you get a right drive. You may want to get a spare drive before these old EFRX drive are not available any more.

Here are the codes for old CMR drives:

WD20EFRX – 2TB  –  Amazon  Ebay

WD30EFRX – 3TB –  Amazon  Ebay

WD40EFRX – 4TB –  Amazon  Ebay

WD60EFRX -6TB –  Amazon  Ebay

You might still get them in some places, but not for long.

 

I hope this helps.

 

Updated table : 23/10/2020

Now also Seagate Skyhawk have few SMR drives. Listed below:

ST8000VX002    ST8000VX008   SMR
ST6000VX011    ST6000VX010   SMR
ST4000VX005    ST4000VX013   SMR
ST3000VX017    ST3000VX016   SMR
ST2000VX012    ST2000VX015   SMR

 

Updated table : 25/04/2020

Model Series Capacity Type Platter
WD10EFRX Red 1TB CMR 3.5inch UK USA
WD20EFRX -old Red 2TB CMR 3.5inch UK USA
WD20EFAX Red 2TB SMR 3.5inch UK USA
WD30EFRX -old Red 3TB CMR 3.5inch UK USA
WD30EFAX Red 3TB SMR 3.5inch UK USA
WD40EFRX -old Red 4TB CMR 3.5inch UK USA
WD40EFAX Red 4TB SMR 3.5inch UK USA
WD60EFRX -old Red 6TB CMR 3.5inch UK USA
WD60EFAX Red 6TB SMR 3.5inch UK USA
WD80EFAX Red 8TB CMR 3.5inch UK USA
WD100EFAX Red 10TB CMR 3.5inch UK USA
WD101EFAX Red 10TB CMR 3.5inch UK USA
WD120EFAX Red 12TB CMR 3.5inch UK USA
WD140EFFX Red 14TB CMR 3.5inch UK USA
UK USA
WD20EZAZ Blue 2TB SMR 3.5inch UK USA
WD60EZAZ Blue 6TB SMR 3.5inch UK USA
UK USA
WD10SPZX Blue 1TB SMR 2.5inch UK USA
WD20SPZX Blue 2TB SMR 2.5inch UK USA
UK USA
WD10SPSX Black 1TB SMR 2.5inch UK USA
UK USA
WD2002FFSX Red Pro 2TB CMR 3.5inch UK USA
WD4003FFBX Red Pro 4TB CMR 3.5inch UK USA
WD6003FFBX Red Pro 6TB CMR 3.5inch UK USA
WD8003FFBX Red Pro 8TB CMR 3.5inch UK USA
WD101KFBX Red Pro 10TB CMR 3.5inch UK USA
WD102KFBX Red Pro 10TB CMR 3.5inch UK USA
WD121KFBX Red Pro 12TB CMR 3.5inch UK USA
WD141KFGX Red Pro 14TB CMR 3.5inch UK USA
WD161KFGX Red Pro 16TB CMR 3.5inch UK USA
WD181KFGX Red Pro 18TB CMR 3.5inch UK USA
UK USA
WD1005FBYZ Gold 1TB CMR 3.5inch UK USA
WD2005FBYZ Gold 2TB CMR 3.5inch UK USA
WD4002FYYZ Gold 4TB CMR 3.5inch UK USA
WD4003FRYZ Gold 4TB CMR 3.5inch UK USA
WD6002FRYZ Gold 6TB CMR 3.5inch UK USA
WD6003FRYZ Gold 6TB CMR 3.5inch UK USA
WD8003FRYZ Gold 8TB CMR 3.5inch UK USA
WD8004FRYZ Gold 8TB CMR 3.5inch UK USA
WD101KRYZ Gold 10TB CMR 3.5inch UK USA
WD102KRYZ Gold 10TB CMR 3.5inch UK USA
WD121KRYZ Gold 12TB CMR 3.5inch UK USA
WD121KRYZ Gold 12TB CMR 3.5inch UK USA
WD141KRYZ Gold 14TB CMR 3.5inch UK USA
UK USA
all models WD HGST alls sizes CMR 3.5inch UK USA

EFRX Price/TB Price Capacity read/write Watt cache Warranty
Western Digital WD Red WD10EFRX 3.5″ SATA 6Gb/s 1TB 5400rpm £54 £54 1TB 150/ 3.3 64 3yr non-SMR (CMR)
Western Digital WD Red WD20EFRX 3.5″ SATA 6Gb/s 2TB 5400rpm £35.5 £71 2TB 147/ 4.1 64 3yr non-SMR (CMR)
Western Digital WD Red WD30EFRX 3.5″ SATA 6Gb/s 3TB 5400rpm £29.33 £88 3TB 147/ 4.1 64 3yr non-SMR (CMR)
Western Digital WD Red WD40EFRX 3.5″ SATA 6Gb/s 4TB 5400rpm £26 £104 4TB 150/ 4.5 64 3yr non-SMR (CMR)
Western Digital WD Red WD60EFRX 3.5″ SATA 6Gb/s 6TB 5400rpm £28.17 £169 6TB 175/ 5.3 64 3yr non-SMR (CMR)
EFAX – SMR Price/TB Price Capacity read/write Watt cache Warranty
Western Digital WD Red WD20EFAX 3.5″ SATA 6Gb/s 2TB 5400rpm £35.5 £71 2TB 180/ 4.1 256 3yr SMR
Western Digital WD Red WD30EFAX 3.5″ SATA 6Gb/s 3TB 5400rpm £28.33 £85 3TB 180/ 4.8 256 3yr SMR
Western Digital WD Red WD40EFAX 3.5″ SATA 6Gb/s 4TB 5400rpm £24.25 £97 4TB 180/ 4.8 256 3yr SMR
Western Digital WD Red WD60EFAX 3.5″ SATA 6Gb/s 6TB 5400rpm £28 £168 6TB 180/ 4.8 256 3yr SMR
Western Digital WD Red WD80EFAX 3.5″ SATA 6Gb/s 8TB 5400rpm £26.88 £215 8TB 210/ 8.8 256 3yr non-SMR (CMR)
Western Digital WD Red WD101EFAX 3.5″ SATA 6Gb/s 10TB 5400rpm £27 £270 10TB 210/ 5.7 256 3yr non-SMR (CMR)
Western Digital WD Red WD100EFAX 3.5″ SATA 6Gb/s 10TB 5400rpm £28.8 £288 10TB 210/ 5.7 256 3yr non-SMR (CMR)
Western Digital WD Red WD120EFAX 3.5″ SATA 6Gb/s 12TB 5400rpm £29.25 £351 12TB 196/ 6.3 256 3yr non-SMR (CMR)

 

What are PMR and SMR hard disk drives?

source: https://www.synology.com/en-us/knowledgebase/DSM/tutorial/Storage/PMR_SMR_hard_disk_drives

Perpendicular magnetic recording (PMR) and shingled magnetic recording (SMR) are technologies used to physically store bits of data onto a hard disk drive (HDD). For HDD manufacturers, one of the most important concerns is areal density, which is the number of bits of data that can be recorded onto a magnetic disk. Areal density is measured by the number of bits or gigabits per square inch, with the higher values allowing for greater storage using the same amount of disk space. SMR offers larger drive capacity than the traditional PMR because SMR technology achieves greater areal density.

This article will give a quick overview of PMR and SMR technologies and highlight key differences between them.

Perpendicular Magnetic Recording (PMR)

PMR, also known as conventional magnetic recording (CMR), works by aligning the poles of the magnetic elements, which represent bits of data, perpendicularly to the surface of the disk. Magnetic tracks are written side-by-side, without overlapping. Because the write head is normally larger than the read head, HDD manufacturers try to shrink the size of the write head as much as possible.

PMR

Shingled Magnetic Recording (SMR)

SMR is an extension of PMR and offers improved areal density. Rather than writing each magnetic track without overlapping, SMR overlaps each new track with part of the previously written track, much like shingles on a roof. By overlapping the tracks, write heads become thinner, thus expanding areal density.

SMR

Differences between PMR and SMR

Regardless of whether an HDD uses PMR or SMR, the read head only requires a small portion of the written magnetic track. When new data is written on an SMR drive, the tracks are fully readable without impacting performance.

However, when the data on an SMR drive is edited or overwritten, the write head will not overwrite the data onto the existing magnetic track. Instead, the new data will be written onto an empty area of the disk, while the original track with the old data will temporarily remain. When the HDD becomes idle, it will enter a reorganization mode where the old bits of data on the original track will be erased and made fully available for future use.

This reorganization mode must occur to completely delete tracks, making the idle time essential for an SMR drive. If an SMR drive is being used heavily for read and writes, it will not have enough time to reorganize the magnetic tracks, causing the tracks with the old data to remain temporarily. As a result, the SMR drive may need to write new data and reorganize the old track at the same time, resulting in a negative impact on the overall read/write performance. To combat this, SMR drive manufacturers have developed firmware that optimizes the read/write performance while data is being overwritten.

Note:

  • We recommend establishing a RAID on either all PMR drives or all SMR drives. If a RAID is established on both PMR and SMR drives, the overall read/write performance may be affected by the SMR ones during overwriting tasks. For details on RAID, please check out this article.

 

Seagate list

  • Barracuda 2TB – 7,200rpm – SATA 6gig – model name – ST2000DM008
  • Barracuda 4TB – 5,400rpm – SATA 6gig – ST4000DM004
  • Barracuda 8TB – 5,400rpm – SATA 6gig – ST8000DM004
  • Desktop HDD 5TB – 5,900rpm – SATA 6gig – ST5000DM000
  • Exos 8TB – 5900rpm – SATA 6gig – ST8000AS0003
  • Archive v2 6TB – 5,900rpm – SATA 6gig – ST6000AS0002
  • Archive v2 8TB – 5,900rpm – SATA 6gig – ST8000AS0002

 

 

List of WD CMR and SMR hard drives (HDD)

 

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