Talk:Fixed-block architecture

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The content of Storage block was merged into Fixed-block architecture on August 7, 2014. The former page's history now serves to provide attribution for that content in the latter page, and it must not be deleted as long as the latter page exists. For the discussion at that location, see its talk page.

CKD versus CHR/CTR

The article mistakes terminology:

IBM mainframe systems' disk layout had traditionally been count-key-data (CKD)…

In fact, the physical layout of the first FBA devices remained precisely the same; it was in the disc controllers that the differences occurred.

CKD had implications for the channel programmer, in that it was possible for a record to be located not solely by its location, but by a key. However, the actual architecture was CHR (cylinder-head-record), also called CTR (cyl-trk-rec). See DASD article.

--UnicornTapestry (talk) 01:06, 7 January 2009 (UTC)[reply]

What is FBA

the article was a mess and I have tried to start to fix it. Is there any substantive difference between FBA and LBA

The RAMAC used fixed sector sizes but I am not sure how the file system accessed it nor how the storage stack was layered. Most of every other early computer that I know of used fixed sector sizes and again i am ignorant of their storage stacks. IBM abandoned fixed sector sizes in most mainframe models with the S/360 beginning 1964. The notable S/360 M20 used a fixed sector size but addressed them with the standard IBM CHR channel commands so it was not an FBA system or drive unless FBA means fixed sector sizes.

To the best of my recollection Fixed Block Architecture is a term invented by IBM with the introduction of the IBM 3310 and a small system (s/34??) sometime in the mid-70s to describe a fixed sector sizes in its HDDs. At that time and into the 1990s IBM used CKD, a variable record length architecture on virtually all of its mainframe HDDs. The rest of the world and I think IBM's small systems used fixed sector sizes.

I know of no other usage of "Fixed Block Architecture" prior to the 3310. To the best of my recollection and search, IBMs other products that used fixed sector (or block) sizes called them just that and did not use the term FBA. I may be wrong and would appreciate other editors input on the origins of this specific term as applied to storage.

The other aspect of FBA is the addressing as a linear contiguous set of blocks. This really isn't a drive issue since drives today still have cylinders and heads and now a variable number of blocks per zone. With fixed blocks, someplace in the storage stack a file name has to be translated into a list or lists of blocks. I really don't know enough about file systems of any of the mainframe any mini computers to know whether the systems went thru a layer where the storage medium was viewed as a linear contiguous set of blocks to be resolved to CHS at a lower level. So it maybe that IBM was first in the 70s, but I doubt it. Again input from other editors would be appreciated.

I really think this is a controller issue, when what was the first controller that presented the device as a contiguous series of fixed blocks. I know this wss a part of the ANSI proposal in the late 70s and was a key feature of SASI. So the earliest FBA/LBA drive that I know of was likely the embedded ANSI drives or maybe the embedded SASI drives.

Comments Tom94022 (talk) 05:41, 9 August 2014 (UTC)[reply]