"Disk is the new Tape" - Not Quite Right. Disks are CD's

Jim Gray, in recognising that Flash Memory was redefining the world of Storage, famously developed between 2002 and 2006 the view that:

Tape is Dead

Disk is Tape

Flash is Disk

RAM Locality is King

My view is that: Disk is the new CD.

Jim Gray was obviously intending that Disk had replaced Tape as the new backup storage media, with Flash Memory being used for "high performance" tasks. In this he was completely correct. Seeing this clearly and annunciating it a decade ago was remarkably insightful.

Disks do both the Sequential Access of Tapes and Random I/O.
In the New World Order of Storage, they can be considered functionally identical to Read-Write Optical disks or WORM (Write Once, Read-only Memory).

As the ratios between access time (seek or latency) and sequential transfer rate, or throughput, continues to change in favour of capacity and throughput, managing disks becomes more about running them in "Seek and Stream" mode than doing Random I/O.

With current 1TB disks, the sequential scan time (capacity ÷ sustained transfer rate) [1,000GB/ 1Gbps] is 2-3 hours. However, to read a disk with 4KB random I/O's at ~250/sec (4msec avg. seek), the type of workload a filesystem causes, gives an effective through put of around 1MB/sec, or 128 times slower than a sequential read.

It behoves system designers to treat disks as faster RW Optical Disk, not as primary Random IO media, and as Jim Gray observed, "Flash is the New Disk".