WD Elements SE 4TB

The Western Digital Elements SE is a 2.5″ inch portable external hard disk, available in multiple capacities. It has the traditional "rounded" shape of WD portable external hard disks, unlike the recent models of WD My Passport disks which have transitioned to a sharp-cornered rectangular enclosure; this makes it a natural fit for the fabled WD Nomad rugged disk cases of old.

• Dimensions: 110 × 81.5 × 21 mm for the 2TB and 4TB variants; the 1TB variant is only 12.8 mm thick.
• Weight: about 250 g (4TB), down to about 130 g (1TB).
• Model: WDBJRT0040BBK-WESN (4TB), or WDBJRT0020BBK-WESN (2TB), or WDBJRT0010BBK-WESN (1TB).

The 4TB WD Elements SE has physical sectors of 4 KiB, but presents to the host system logical sectors of 512 bytes; this makes it a 512e Advanced Format disk, which helps with compatibility with more simple-minded operating systems; because the disk presents 512 byte logical sectors, it must be formatted with the GPT partitioning scheme. The disk has 7,813,969,920 logical sectors, which means that its capacity is 4,000,752,599,040 bytes (3.64 TiB). Crystal Dew World's CrystalDiskInfo says that the disk spins at 5400 rpm.

C:\> fsutil fsinfo ntfsinfo A:
...
Number Sectors :                  0x00000001d1bfa7ff
Total Clusters :                  0x000000003a37f4ff
Free Clusters  :                  0x0000000027ae5d79
Total Reserved :                  0x0000000000000000
Bytes Per Sector  :               512
Bytes Per Physical Sector :       4096
...

The performances as measured CrystalDiskMark are consistent with a 5400 rpm disk with an USB 3.0 connection. Sequential read speed is about 87 MB/sec (or about 83 MiB/sec in binary units); for small random accesses the read speed drops to about 0.5 MB/sec, corresponding to a respectable 133 IOPS. (The write speed as measured by CrystalDiskMark for small random accesses is unrealistic and should not be taken into account.)

In a practical test, reading 2000 photos totalling 15 GB (13.9 GiB) took 236 seconds, coming to 63.6 MB/sec or 60.6 MiB/sec.