Future storage technologies and Linux [LWN.net]

Future storage technologies and Linux

Posted Apr 8, 2011 23:10 UTC (Fri) by giraffedata (subscriber, #1954)
In reply to: Future storage technologies and Linux by pr1268
Parent article: Future storage technologies and Linux

While some may say that disk drives - rotating storage - are on their way out, the fact of the matter is that the industry shipped a record 650 million drives last year and is on track to ship one billion drives in 2015.

Doesn't the concept of a "drive" include any persistent storage medium, including SSDs?

In this case, it is extremely clear, to me, that "drive" is an abbreviation referenced back to "disk drives - rotating storage" in the previous sentence.

Exactly what a "disk drive" is depends on what level you're considering. The characteristics of a disk drive depend on the level at which you look. At one level, a disk drive is a volume of storage, so e.g. a ramfs filesystem shows up in a desktop GUI as a "drive." At a lower level, it's something that behaves like a block device, so the ramfs filesystem doesn't make the cut, but soldered-on flash memory with a block driver does. Going lower, it's something with an ATA or SCSI interface, so the soldered on flash isn't a disk drive, but a logical volume on a RAID array is. At another level, a disk drive is something you plug into a disk drive slot, so a logical RAID volume isn't, but a 2.5" Seagate SATA SSD is. And finally, if you're a disk drive developer, a disk drive is something with rotating disks in it.

I don't know Blackberry, but my pocket computer has no disk drive legacy (never uses the word "drive"), so the SD card in it is not a disk drive, but if I put the same card into my Ubuntu netbook, it could be one.

The "D" is SSD was originally "disk" and SSD was intended to be the oxymoron it is, to make the point that its a disk drive for every purpose except actually being one. Now, people often say "device" or "drive" to avoid the contradiction, but it doesn't work, because a storage device that doesn't emulate a disk drive -- at some level -- isn't an SSD. And by the way, there isn't anything to "drive" in an SSD, so that's still an oxymoron.

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