NAND memory is used in solid state drives (SSDs). It is the “solid” part as opposed to spinning magnetized platters in a hard drive.
Larry O'Conner of OWC writes:
The NAND shortage has really impacted a wide variety of SSD availability... will get a bit better by next week - and will be much improved by the 2nd week of January.
Been frustrating for all - but on the bright side we have caught most backorders up or will have caught up to within last 5-7 days at worst by end of this week on items still not in stock for immediate ship out.
MPG: this also explains why SSD prices have held stable or gone up slightly. It will be nice to see a conventional downward price trend resume, so that my favorite SSDs and my big Time Machine backup SSD become more accessible to more people.
A 960GB SSD is a Good Thing for any Mac, and enough lightning fast storage for any need. The 960GB is actually much faster than most any 3G SSD because it is a RAID-0 stripe internally.