What do the numbers on Western Digital drives mean?
The MDL number consists of the model and firmware,
MDL: WD5000BEKT-00KA9T0
Model: WD5000BEKT
Firmware: 00KA9T0
The model number itself is described extensively in this PDF if the drive was produced after 2005 which does not touch on Firmware. The Model number is a serialization of
- Initials WD
- Drive Capacity and Form Factor
- Business Unit/Brand
- RPM/Buffer Size or Attribute
- Interface Controller
The DCM is the (Drive Configuration Matrix) is used for matching head types, media, pre-amp etc. source There isn't much documented on this but here is a description from a form post
1- Motor (H)
2- Base (S)
3- Latch (E)
4- Bottom VCM (H)
5- Media (Y)
6- Headstack (V)
7- Actuator-Preamp (2)
8- Top VCM (A)
9- Separator (H)
Here's a July 2012 Western Digital document about how to interpret WDC model numbers, for drives produced since December 2005.
https://www.shoprbc.com/images/products/rbc_icecat/documents/058/mmo_31095058_1496050277_692_31784.pdf ("Model Number Format for OEM and Distribution Channels")
That appears to be the document which Matthew Williams cited in a comment above (and Evan Carroll cited shortly afterward in his answer), but the link which they gave has gone dead.
It's not quite up-to-date; here're some additions I've noticed.
2012 version:
3 Capacity Unit/Form Factor
K GB/2.5-inch (12.5 mm z-height)
...
5 RPM/Buffer Size or Attribute
A 5400 RPM with 2 MB cache
B 7200 RPM with 2 MB cache
should be:
3 Capacity Unit/Form Factor
K GB/2.5-inch 12.5mm (old), or 10+TB/3.5-inch (recent drives, like WD121KFBX)
...
5 RPM/Buffer Size or Attribute
A 5400 RPM with 2 MB cache (old), or 256 MB cache (recent drives, like WD20EFAX)
B 7200 RPM with 2 MB cache (old), or 256 MB cache (recent drives, like WD20FFBX)
...
W 7200 RPM with 128 MB cache (like WD4002FFWX)
Z 5400 RPM with 128 MB cache (like WD20SPZX)
Also, some of the larger "Purple Surveillance" drives break the rules. They all have model numbers ending in "PUR_" even though some models (like the WD121PURZ) spin at 7200 RPM instead of 5400, and/or have more than 64 MB of cache. (The "R" normally means 5400 RPM & 64 MB cache.)
Here's a similar document from 2009, which also included model numbers for external drives, and "product codes."
http://fibrevillage.com/files/Western_Digital_Model_Numbers.pdf ("Model Number Format for WD Products")
The following document is for older drives. ("WD internal drive model numbers issued prior to December 2005, retail channel model numbers issued between June 2005 and July 2009, and legacy order numbers issued prior to June 2005.")
https://geeksalive.com/WDC/Western_Digital_Legacy_model_numbers_18079990.pdf ("Legacy Model and Order Numbers / Retired Model and Order Number Formats for WD Products")