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RAID levels not intuitive in anaconda GUI



Based on recommendation moving discussion from bug https://bugzilla.redhat.com/show_bug.cgi?id=874068 to anaconda-devel-list. Initial posts can be found in that bug.

If you are willing to discuss my notes, please keep me on cc list as I am not subscribed in anaconda-devel list. Thank you.

>To address the concerns you specifically wanted explicit addressing:
>
>> * multiple usage of term redundancy/redundant for few checkboxes.
>
>The term 'Redundancy' is used once on the RAID configuration screen, I'm looking at the screen now. It is used once, not multiple times. If that isn't what you meant, please clarify.

On this screenshot (attached to original bug):
https://bugzilla.redhat.com/attachment.cgi?id=640017

First checkbox has label 'Redundancy', last checkbox has label 'Redundant'. In my understanding same terms. Additonally they aren't different by any means, just two equivalent checkboxes for 'redundancy' in same group.
Btw that 'RAID6' label visible on the screenshot does not bring any light to selected configuration.

>> * error detection is feature of all RAIDs but RAID0, levels can't be 
>> differentiated
>
>This is incorrect, Marian. Neither RAID0 or RAID1 have error detection. 
>
>https://en.wikipedia.org/wiki/RAID#Standard_levels

Linked section does not seem to mention error detection for any RAID level at all (maybe following table, however that clearly states RAID1 is able to detect/tolerate failure of n-1 drives which is far away best error detection/correction from all other levels).

Contrary last sentence of top-level initial paragraph of same wiki page clearly states:

  RAID levels > 0 provide protection against unrecoverable (sector) read errors, as well as whole disk failure.

Additionally md manual page (try man md or read http://linux.die.net/man/4/md ) states exactly same in section RECOVERY:

  If the md driver detects a write error on a device in a RAID1, RAID4, RAID5,
  RAID6, or RAID10 array, it immediately disables that device (marking it as
  faulty) and continues operation on the remaining devices.

Marian is right, wiki as well as man md agree with him, all RAID levels except of RAID0 do error detection.

Therefore I say that usage of term 'error detection' is highly confusing as it actually counts wide range of RAID levels, RAID is error detecting redundant composition of disks by definition (once more, many professionals do not count RAID0 to RAID family).

>> * concern that 'common terminology' used in anaconda is not used anywhere else.
>
>If you read comment #10 again, you will see I wrote the following:
>
>in the RAID # format ("common terminology").
>
>I was referring to the RAID # format (RAID ), RAID 5, RAID10, etc) as the "common terminology" as that was what Martin called it in comment #0.

This confusion is caused by insufficient description of my intention, that's my fault sorry for that. I'll try to correct it. I absolutely agree with initial reporter of reffered bug, Martin Banas, that common terminology is crucial for easy adoption of new RAID handling. In my opinion it is absolutely necessary to bring similar naming as other products providing RAID capability such as BIOS RAID, full featured RAID controllers or other operating systems. I am afraid that terminology introduced in new anaconda isn't used by any similar product and as such it tends to be highly confusing (it is highly confusing to me for all expressed reasons). Therefore I asked to show usage of approach also in other products. I hope it is much clearer now.

Well, this is it. Last but not least initial message of bug https://bugzilla.redhat.com/show_bug.cgi?id=874068 describes issue with current implemetation of RAID definition in really specific comments as is and it does not deserve to be closed/rejected without further discussion/research.

As the anaconda implements creation of MD devices it would be really nice to have it aligned with MD terminology as expressed in relevant man pages.

Thank you very much for audience.

Regards, 

Marian 


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