Talk:RAID

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Former good article nominee RAID was a Engineering and technology good articles nominee, but did not meet the good article criteria at the time. There are suggestions below for improving the article. Once these issues have been addressed, the article can be renominated. Editors may also seek a reassessment of the decision if they believe there was a mistake.
May 22, 2006 Good article nominee Not listed
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Merger proposal[edit]

The following discussion is closed. Please do not modify it. Subsequent comments should be made in a new section. A summary of the conclusions reached follows.
The result of this discussion was to not merge. – voidxor (talk | contrib) 03:37, 3 February 2015 (UTC)

I propose that Standard RAID levels be merged into RAID. I think that the content in the Standard RAID levels article can easily be explained in the context of RAID, if it is not already. I cannot justify the duplication of effort when it comes to listing RAID levels. One example is the recent addition of a table of levels to the Standard RAID levels article, when a much more established table of differences already exists in the RAID article. Listing basic RAID levels in two places is redundant, so I removed it. I felt bad when doing so because an editor worked hard on the new table, having not seen the existing one. It's easy to see how one would land on Standard RAID levels and assume they are on Wikipedia's one-and-only RAID article. – voidxor (talk | contrib) 06:49, 23 January 2014 (UTC)

  • Oppose: From one side, that totally makes sense, as that way some content would be deduplicated. Though, if we do that, then merging Nested RAID levels and Non-standard RAID levels is also on its way, what would simply make RAID article too large. Also, there's more room for improvements to the Standard RAID levels article, in form of more content to be added, what additionally supports the counterargument of RAID article becoming too large. — Dsimic (talk) 14:53, 23 January 2014 (UTC)
    I disagree that this merge would be a gateway to merge Nested RAID levels and Non-standard RAID levels; those topics aren't nearly as duplicated on RAID as the standard levels. Also, while your recent edits to RAID help to clarify that it is not the authoritative article on the levels, perhaps you should have waited until this discussion was closed before you changed the status quo! – voidxor (talk | contrib) 06:48, 24 January 2014 (UTC)
    I apologize, doing that edit was too much of "going ahead" from my side. Sorry! :( At least, I hope you agree that it made the layout of RAID article much cleaner.
    How about, maybe, a different approach – moving the content of RAID § Comparison section into the Standard RAID levels article? That would be another approach to deduplication of the content, while keeping (and improving) current relation between these four articles. Also, we could add a hatnote to the "Standard RAID levels" article (and to "Nested RAID levels" and "Non-standard RAID levels" as well), pointing out the existence of an important "umbrella" article to anyone landing there.
    Another reason behind opposing your proposal is that the merge would make "Nested RAID levels" and "Non-standard RAID levels" articles (and their summary sections) visibly much less valuable, thus more likely to be skipped by the readers. On the other hand, if we move the "Comparison" section as I just proposed, the "umbrella" article would provide an equal treatment to all categories of RAID configurations, achieving the content deduplication at the same time.
    Thoughts? Once again, I apologize for running too fast. — Dsimic (talk) 19:44, 24 January 2014 (UTC)
    I agree that your edits made it cleaner (which is normally a good thing), but I hope it does not affect the balance of this debate. Otherwise, apology accepted. Relocating the Comparison section into the Standard RAID levels article is another option for voters, but I am the nominator and thus recuse myself from commenting on it. Again, I would not worry about Nested RAID levels and Non-standard RAID levels right now as the majority of readers are here for levels 0–6. – voidxor (talk | contrib) 07:01, 25 January 2014 (UTC)
    Thank you. Let's see what the other editors are going to say. — Dsimic (talk) 17:18, 25 January 2014 (UTC)
  • Oppose: This is used by people in the workplace who want a quick reference. It works well and I refer to it 2 times a week. — Preceding unsigned comment added by Lkshoe (talkcontribs) 17:01, 14 February 2014 (UTC)
    This discussion is debating whether the information from both articles should be merged into one; nobody is suggesting deleting the reference information. – voidxor (talk | contrib) 00:24, 20 April 2014 (UTC)
  • Oppose: The article's overly-long as it is; arguably more of it should be split to sub-articles. Chris Cunningham (user:thumperward) (talk) 13:06, 8 April 2014 (UTC)

The above discussion is closed. Please do not modify it. Subsequent comments should be made in a new section.

Reliable single disks[edit]

A recent edit by Snori describes super-expensive SLED devices as “super-reliable” and the smaller, less expensive disks as “comparability unreliable”. That's not actually true, and I think it skews the description of the basic idea behind RAID.

  1. No one in 1987 thought the reliability of disk storage was a big problem. Although rotating disks, as moving parts, are more likely to wear out under normal use than purely electronic parts, that failure rate was still not very high.
  2. The original RAID paper by Patterson et al. cites about the same mean-time-to-failure rating for all of the disk drives mentioned, tens of thousands of hours of operation; in fact, the biggest-and-most-expensive mainframe disk (IBM 3380) and the smallest-and-least-expensive PC disk (Conner CP 3100) have exactly the same MTTF rating (30,000 hours).
  3. The emphasis on redundancy in RAID is because the overall reliability of an array drops by a factor of the number of drives involved. One small drive may have a MTTF of three or four years, but an array of 100 small drives might be expected to have a drive failure within two weeks. That's why redundancy was necessary, not because the individual drives were unreliable.

The leading motiviation to develop RAID was the higher performance which could be realized; associated benefits include larger and more flexible storage capacity, and reductions in equipment cost, size, and power consumption. Single disk reliability wasn't a big factor.  Unician   07:52, 1 September 2014 (UTC)

Well spotted! I suspect that they *suspected* that the inexpensive drives were less reliable (despite having the same stated MTTF figures), but the key issue re of an array of inexpensive disks is not that the drives themselves are less reliable, but that the array *itself* is less and less reliable the more drives it contains.Snori (talk) 01:53, 2 September 2014 (UTC)

Early RAID 2[edit]

@Dsimic:The 3330, actually the 3830 storage control used a Fire code appended to the end of each block for error correction. It was not a Hamming code as used in RAID-2. More significantly, the Hamming code works in real time while the appended Fire Code works after a block has been buffered; so the reference to the 3330 should be deleted, regardless.

I am very certain that the 353 did use a Hamming code so it that sense it was similar to RAID-2. It was actually a Redundant Array of "Independent" Heads, 40 heads transferred in parallel, 32 data, 7 Hamming code and 1 parity. That's why the term "similar approach" is used in the article. I'd have to dig a bit to find a reference if this is disputed, but I am sure i can find one. Tom94022 (talk) 01:55, 15 January 2015 (UTC)

e.g., see page 157 of IBM 7030 Data Processing System Reference Manual; it discloses 32 data bits plus 7 ECC bits in the "high speed disk storage unit" which I am pretty sure is the IBM 353. Tom94022 (talk) 18:27, 15 January 2015 (UTC)

If you cannot find a clear and credible source that states what the article states, it doesn’t belong. Personal interpretations of technical material isn’t suitable. Strebe (talk) 07:33, 16 January 2015 (UTC)
There is at least one reliable source that the 353 was the disk file on the 7030. Tom94022 (talk) 08:27, 16 January 2015 (UTC)
That has nothing to do with it. The question is what any of this has to do with the article. Unless the source specifically notes the similarity of the 353 to RAID, then what you have is unverifiable WP:SYNTH and WP:OR. The debate going on above clearly demonstrates this. Strebe (talk) 11:00, 16 January 2015 (UTC)
What is left to debate? It is well established that both the TM and the 353 had 32 bit data words with parallel real time 7 bit ECC. It is also well established the 3330 used a serial (Fire code) ECC. 17:47, 16 January 2015 (UTC)
That entire list claiming “each of the five levels of RAID named in the paper were well established” has to go. The Wikipedia article is creating an account of history, and that is not allowed. Strebe (talk) 07:01, 17 January 2015 (UTC)
Hello, and sorry for my delayed response.
Regarding the "well established in the art" sentence, it's pretty much fine as it explains that the technology behind different RAID levels already existed in various products before "RAID" itself was coined as a term and the RAID levels were defined. Speaking of Wikipedia's history collection role, that sentence actually supports it by providing a more detailed timeline description.
Thank you very much, Tom94022, for clarifying the whole thing! I've added two references into the RAID § History section that confirm that IBM 353, as part of IBM 7030, used ECC codes. — Dsimic (talk | contribs) 16:18, 17 January 2015 (UTC)
This article expresses research done by editors (WP:OR) in the form of collecting information about certainly early computers. Then it draws connections (WP:SYNTH) between the topic (RAID) and the computers that those editors believe express RAID characteristics. Those connections have to be drawn by credible sources, not by Wikipedia editors. Please read those policies so that you understand what I mean and why the practice is not appropriate. Strebe (talk) 22:39, 17 January 2015 (UTC)
Finding reliable sources is not original research and synthesizing from them is permitted. Tom94022 (talk) 23:53, 17 January 2015 (UTC)
Yeah, otherwise we'd be just copying and pasting from sources, what wouldn't make much sense. In the end, even rephrasing the sources could be seen as some kind of a synthesis. — Dsimic (talk | contribs) 02:15, 18 January 2015 (UTC)
I don’t know how to be more plain, particularly if you are unwilling to even try to understand the policies. Have you read them? These edits draw conclusions beyond those found in the sources. I do not dispute the sources, but the sources say nothing about RAID. Tying RAID to the sources is WP:SYNTH. It is not allowed. What •is• allowed is for you to research sources that describe the historical background of RAID, and to state the conclusions of those sources. Whether rephrasing could be seen as some kind of synthesis is irrelevant; I’m not interested in debating Wikipedia policy. Policy is as clear as feasible, and it contains answers to such questions. Instead, I’m interested in the article having reliable sources. The synthesis of editors is not a reliable source. Please find sources that state these connections between the listed computing devices and RAID. Strebe (talk) 03:12, 18 January 2015 (UTC)
Yes, I've read the guidelines long time ago, and I still know them. Long story short, I'll try to find more references to additionally tie everything together. Please, just give me some time. — Dsimic (talk | contribs) 03:38, 18 January 2015 (UTC)
Ok, found and added a really nice reference in which Randy H. Katz, one of the authors of the RAID publication described in RAID § History section, clearly confirms it:
We were not the first to think of the idea of replacing what Patterson described as a slow large expensive disk (SLED) with an array of inexpensive disks. For example, the concept of disk mirroring, pioneered by Tandem, was well known, and some storage products had already been constructed around arrays of small disks.
This clearly takes WP:SYNTH out of the equation. Hope you agree. — Dsimic (talk | contribs) 05:10, 18 January 2015 (UTC)

──────────────────────────────────────────────────────────────────────────────────────────────────── Dsimic nice find with the Katz quote. I believe I heard him say the same thing at some point but didn't bother to look for it because Strebe mis-states what the article says and then mis-applied WP:SYNTH. The RAID paper defines RAID-1 as disk mirroring. The literature of the far earlier DEC product discloses disk mirroring. It is no violation to then say disk mirroring existed before the term RAID-1 was defined. Ditto for each of the other RAID levels and for the introductory sentence. But that is moot now, thanks to yr great work. Tom94022 (talk) 07:46, 18 January 2015 (UTC)

Thank you very much. The whole thing clearly wasn't a case of WP:SYNTH or WP:OR even before this additional reference, but hey, now we know for sure that the sky is usually blue. :) — Dsimic (talk | contribs) 08:02, 18 January 2015 (UTC)
That’s considerably better. Technically it’s still not sufficient, but I doubt you’ll get too much blowback, though it would not surprise me if some “cite” templates sprouted somewhere along the line on individual examples. I’m afraid your opinions about WP:OR and WP:SYNTH do not reflect policy. In order for that section to be up to snuff, a credible reference must state that all the elements (not some) of RAID were already in place by the time the concept was formalized, and the specific examples in the list would have to appear in some reference as examples of RAID, not as examples of disks that Wikipedia editors have themselves deemed meet RAID characteristics. Without those qualifications being met, anyone can come along and question whether the edits comprise WP:NOTABLE material by pointing out that, if Wikipedia editors had to make those associations (WP:SYNTH), it means the material is not WP:NOTABLE. I’m not going to spend more time on this topic, but again, I urge you to hone your understanding of the policies and their purpose since any similar edits you make are likely to be challenged eventually. Strebe (talk) 02:27, 19 January 2015 (UTC)
Please don't get me wrong, but I see that as unproductive nitpicking. While the RAID § History section is very well covered by references, there are numerous other not-so-short articles with very few or even zero inline references, and nobody questions them. If we'd go strictly by the guidelines, such articles would be giant WP:SYNTHs or WP:ORs and should be immediately deleted. — Dsimic (talk | contribs) 03:53, 19 January 2015 (UTC)

RAID 10 is a nested (hybrid) level[edit]

Hello, 67.6.185.65! As I've noted in my edit summary, RAID 10 is a nested (hybrid) level, not one of the standard RAID levels. Thus, it is wrong to add RAID 10 into the RAID § Standard levels section; please see RAID § Nested (hybrid) RAID section for further information. — Dsimic (talk | contribs) 20:01, 14 April 2015 (UTC)

Reference websites and other stuff[edit]

Hello, A876! Regarding your edit comment, there are three things:

  • Nobody owns anything, as you've described it for some reason; what I've done is called peer review and articles actually benefit from it. Moreover, it would be great if many more articles had active peer reviewers.
  • Article-level consistency should be more important than using all of the possible variants, and almost all references in this article have domains or hostnames for the values of their |website= parameters (where applicable, of course).
  • Wording can always be better, and small mistakes or typos should be discussed or corrected in a friendly manner instead of beind called "cruft" that's "proudly" put into an article. If there's anything causing a disagreement, we're here to discuss it.

With all that in mind, I've restored the references and improved the wording a bit further. Hope you agree. — Dsimic (talk | contribs) 22:30, 20 April 2015 (UTC)