Facilitate the conversation: say what you mean and don’t make assumptions

We all work with words every day. Words that can cause confusion if used incorrectly, but words can also make the conversation smoothless … if used correctly.

I’d like to name a few of these possible confusion from my daily experience in the IT Storage business.


  • Network versus fileserver

How many of you store their data on the network? The network connects clients to servers (or other clients). The network consists of network devices like switches, routers, bridges, firewalls and the cables to connect all these devices together. I store my data on a file server and the network helps me getting it there.

  • SAN vs Storage (Array)

SAN = Storage Area Network = the network that connects devices who need to talk to each other (examples for these end nodes are HBAs, tape libraries and storage arrays).

Storage Array = the device that provides storage capacity to hosts using some protocol using a SAN to get the bits and bytes transported.


  • Hyper / Slice / split versus device

In the (EMC) enterprise class storage arrays Symmetrix and VMAX devices (symdev, tdev) group disks together like Raid Groups. Each maskable device (which a host sees as a LUN) is made up out of data and parity information (or 2 data pieces if you’re using RAID1). Each data or parity piece comes from a single disk (spindle). So in a way each disk is eventually sliced up into slices and for example a 3RAID5 devices is made up out of 4 slices, 3 data slices and a parity slice. A slice is also called a hyper. So if you say slice, you actually mean a non maskable piece of a single disk. Several of these slices form a maskable device called a LUN (as seen from a host).


  • Gigabyte versus Gibibyte

Back in the old IT days we used to call 2^10 bytes a kilobyte, because the 1024 was almost the same as 1,000 which is kilo. Then we got the MB and GB (and on and on and on) and the deviation from the original number became significant. In the year 2000 the IEE adopted the IEC recommendation to use a different presentation for the binary counts. Giga still means a billion, but 1024x1024x1024 is now called a binary Gigabyte, a Gibibyte. The binary equivalents are kibi (binary kilo), mebi (binary mega), gibi (binary giga), tebi (binary tera) and so on. Wikipedia has a nice table on this subject: http://en.wikipedia.org/wiki/Gigabyte. Please note that 1 binary kiloytes is spelled as 1 KiB, not kiB. The “Ki” was introduced to match the use of the capital M in MiB, the capital G in GiB and so on.

Even the IEC wrote an article on the “new” binary prefixes in … 1999 !!!!!! –> http://www.iec.ch/tcnews/archives/pdf/tclet6.pdf

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