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How Are RAID Arrays Identified By Hardware?
Coward Anonymously Before Me asks: "This is more of a tech/hack question, but recently my highpoint controller forgot my disks were in a raid array. All the Disks still function, and have ZERO problems, aside from being not identified as still in RAID-0. All the data should still be there, but remains unaccessible to me, thus the question how and where would this kind of information be stored? On chip? MBR? and can the data be recovered without 3rd party interaction via free/open source toolkits? or even purchased software?"
...you ought to be able to just dd the data from the drive, and if the chip doesn't use a non-standard data layout, write a program or script to put it back together and back it up, then you recreate the array, and put your data back on it.
A solution to the problem with music today
Typically, there's a utility in the RAID configuration that stamps the drive as part of a set, marks the state (good, bad, rebuilding or hot-spare are most common) and some kind of versionig information.
I've ripped a few disks out of the array, mounted them as standard, reformatted and replaced the MBR, threw them back in the array, and still had them recognized as part of the RAID volume. The RAID card didn't like this much, however. :)
I think your best bet is to talk to one of the people who actually wrote the drivers for the card (you've got the Linux source, right :) or possibly see if you can get ahold of an engineer at the manufacturer and discuss ways of getting the information back.
Good luck!
There's so little difference between politics and jihad lately...
...I went to Google and found this:
"Where does the controller store its configuration? Disk, Ram, Rom ? Can it be saved or exported as a backup?
The config is in NVRAM on the controller, but there's also about a 4MB
"partition" (not really a partition, but config area) on each drive in the
array that stores information on things like position in the array, etc.
Alternately, try this link for the whole thread on the subject.
It literally took me 30 seconds to find it. Next time, try Google before posting, mmkay?
Cruising the internet on my TI-99/4A @ a whopping 300 baud!
Logical volume managers (AIX and Veritas anyway) store a unique ID on the disk, and then keeps track of what volumes are there, how they are configured, etc.
Hardware controllers generally reserve a small slice of disk to store configuration data. Sometimes this slice is marked unusable and can only be accessed by low-level hardware.
One of the big, unadvertised problems with RAID, particularly with new/buggy controllers, is that a controller failure can trash your data.
Unless you have the time & knowledge to reconstruct the data structures, a controller failure that screws up the configuration data on disk effectively destroys your data.
Conformity is the jailer of freedom and enemy of growth. -JFK
When questions like this come up in our daily tech life we don't just think "Oh! I'll goto google and get an answer!" Some of us are community conscience and think "This is an interest problem, I bet the /. community would be interested in the answer." Of course when we have these thoughts we forget how unforgiving some readers are *cough*
I have great faith in fools; My friends call it self-confidence. Edgar Allan Poe 1809-1845
I think he posted to the wrong topic, note the next story. However, he's a troll, so it doesnt matter either way.
-- 'The' Lord and Master Bitman On High, Master Of All
people get annoyed with me that I ask questions on IRC or message boards which are covered thoroughly in manuals. They respond with, of course, "RTFM"
Am I the only one who thinks that a Manual is a pretty lame source of information to reach for first-thing?
I have a few sources I go through, usually the manual is one of them, but I _Always_ first ask a person who might have the answer on hand. Manuals are not often things which lend themselves to answering typical questions such as "Can I blah?". The problem with "Can I blah" being looked up in a manual, among other things, is that often there are numerous synonyms for 'blah', and only one of them is ever used in the book, especially the index.
Perhaps they mean "Read the entire manual before even using the product". The obvious problem here is that manuals are getting longer every day. I've heard that some Linux Distro comes with a 2000 page manual just for getting it installed. Obviously, to read an entire manual before using a product would leave little time for using any products, and leave you more or less unknowledgeable about the product.
Then there's the problem of phrasing. Manuals may answer your question, but only burried in a lot of other information which isnt related to what you're actually working on. A person who knows already, however, can simply answer your question.
Slashdot, however, is far too public and non-specific. There's no reason to ask this kind of question on slashdot, get some friends or something.
-- 'The' Lord and Master Bitman On High, Master Of All
Unless I misunderstand - your system *is* broken without the controller anyways right? So why not just replace it?
.sig wanted: Must be concise, funny, and display my cleverness.
If everyone was like you, people who really needed help with issues that were *not* in the FM would never get it. Forums like usenet, irc, and even ask /. are there to discuss novel issues, not to re-hash old topics over and over. People who ask questions before they RTFM are a detriment to the online community. We are *all* fortunate that people put with the likes of you.
When you *do* RTFM, not only do you get better at manual reading, but you also pick up additional information, so you may be less clueless the next time you have a problem
-BP
If your controller just spontaneously lost it's configuration, it's a problem with the card. Call the manufacturer and get a replacement. If they will configure it for you before they send it (which shouldn't be difficult for them), you should be able to just swap it in and go.
You'll need to do something like this, since you won't be able to get at the data on the drives unless you can hook them up to a RAID controller that will recognize the particular flare code etc of your setup.
If you can stomach losing the data (you backed up the important stuff, right?) then you could try starting over from scratch, but I would not trust your RAID controller if I were you. Replace it or don't use it.
Under capitalism man exploits man. Under communism it's the other way around.
I've worked quite a bit with AMI controllers and Adaptec. At work we looked at using an Adaptec ZCR card but chose not to for the following reason.
AMI Megaraid(and now LSI) write a bit of config info to each disk and to the controller. On these cards, you need to know the drive designations (which is drive1, which is drive 2, etc and the stripe size (how much data to write to the first disk before moving on to the second). On these controllers, if your card goes belly up you can usually put in a new card which will detect that your drives still have a configuration and use it. Otherwise, you can create a new configuration of the drives (same raid level, same stripe size, each drive with same designation) and it will access the data just fine on a reboot. (probably 75-85% of the time. The rest of the time you are just SOL and need to get out tape.)
Adaptec's ZCR card we were testing and going to ship had the unfortunate effect that when an array was created, it immediately initialized (format) all the data.
This is something you should check into. Perhaps the highpoint card will let you make a new array and reboot. Or it might automatically initialize and wipe out all your data before letting you use it.
Hope this helps
--
I had a very similar thing happen to me a while back. It was caused by a hardware problem (I was using a pair of IBM deskstar drives), so I never did recover quite all the data, but I did manage to get the RAID array back together. By a lucky coincidence, this happened shortly after drivers/ide/hptraid.h was added to the linux kernel, so I had somewhere to look for inspiration.
This file describes the structure of one sector somewhere near the start of each disk. (Sorry, I don't remember exactly which one.) The magic number had changed on one of the disks from HPT_MAGIC_OK to HPT_MAGIC_BAD. Editing it back again was sufficient to reconnect the drives.
I accidently deleted my first reply to this so I'll make this one brief. It seems there are just as many, if not more, hits on google that deal with Linux than Windows (about 54 vs 59 million for linux vs microsoft. accounting for windows pages not dealing with computers, I'd say they're about even). There are certainly more linux "answers" out there than windows, its just that most of the linux answers that you need are probably basic enough that most of the people running linux don't ask them. Windows is incredibly difficult to find information for. Once you get into hardcore networking and stuff like DCOM and intricate implimentations thereof, you're out of luck in the windows world.
"Nature doesn't care how smart you are. You can still be wrong." - Richard Feynman
1) Backup the drives manually just in case (copy the raw drive data off to tape after booting from CD or floppy).
2) Go into the hardware raid setup and set the array up exactl as before, but dont let it initialize. If your hardware raid controller always initializes new divces by writing over them with zeros or something, this might be undoable or tricky. If you end up initializing, it's not that big a deal.
3) If you did it without initializing, you're probably good to go. If you ahd to initialize in order to configure the array, now boto off of CD again and restore the raw drive images from tape.
Done
11*43+456^2
given that a large portion of the documentation for a distribution is available on the computer, one might try searching through the documentation with the computer, if the index is not sufficent.
man and info both support searching (with the / key in both, i believe)
most of the documentation for linux/unix that is not in man or info pages is in html, and most web browsers also support searching, although the key may vary
Need a Catering Connection
I explain to people how to burn cd's every day, some of them can't figure out something that technical on their own. Other's know that I can show them in 5min what would take them hours to figure out on their own. All of them know I'm busy and understand I'll get there whenever I can. Yes it's frustrating to answer simple questions, but there is a big difference between "how do I click a mouse?" and "how do I burn a cd?" The person who is asking how they burn a cd, has at least done enough looking around to find out that what they want to do is burn a cd.. maybe they are trying to reach a different end goal and burning a cd is one of the things they want to try along the way. Maybe their really trying to transfer files from one machine to another or find a reasonable way to share bulk files with friends and have just spent a few hours trying to research how to get to the point where they've got those bulk files (perhaps a family history album, this is recent real world example I helped someone at this point with). Just because the question they ask has a simple solution for someone who has already figured it out, or has another possible source of information, doesn't mean they haven't tried to figure something out for themselves.
Maybe they don't know there are such things as search engines yet, maybe what they really need help with finding that information out, perhaps along with the answer to their original question you could explain search engines, I'm sure they would really appreciate that.
People often have different reasons, they may just have a different knowledge set than you. They may not be as intelligent, and where you were able to interpret the information you found during a google search easily, they need someone to translate it into something a little more user friendly before they will understand it. Perhaps as I said earlier, they are frustrated and need a simple answer before they can move back to tackling their real issue.
I don't know about you, but I work in a tech shop, all day long we ask each other questions, a great deal of them simple, it's only when someone else isn't available or the others don't know that you resort to a web search that takes more time. I'll evaluate how important it was for you to spend 5 minutes to answer a question I would have had to spend 2hrs figuring out on my own when you need to know something that I have experience with and could answer in 5mins and will save you 12...
Volunteers can do whatever they wish, be as friendly or not friendly as they wish, they can cater to whatever technical degree they wish on a given subject... but they certainly have no reason to flame those who have simpler questions, if you tired of it, or would rather help with more difficult things, so be it but that's an excuse for not answering it's no excuse for "RTFM".
I will say this though, I've spent a great deal of time on help channels.. both giving and recieving information. One, if you give information where you can, your more likely to get the information you need without a hassle. And two, if you tried to find the information and couldn't, someone will usually point you to it, even if they do so in the form of a flame. And three, if you did find the information, are bright enough to mention what you weren't clear on, someone will usually phrase it in another way or otherwise clarify even if it is in a exclamation that ends in "you fucking n00b".
The real question you should be asking yourself is, of course, "Where are my backups?"
Anyone know where I can find information on the Rockridge standard? I can't find it anywhere and I heard it can burn files to CD including permissions information, I need to get specification though since I need to have each .iso generated by a script.. :D
What? I figure we're off-topic enough already as it is
Though it does bring up an interesting point that some people really just need to know where a manual is, or if one exists. Manpages often tell everything you could ask for regaurding command line switches, but doesnt talk at all about the interface, or even what it is the program does. The most helpful source of information could be burried in a seemingly unrelated HOWTO which you'd never know to search for without knowing the program's intended function in the first place [you just found it in some error report from cron]
I get the feeling that a lot of people who say "RTFM" havent actually read the specific manual in question, they've learned from others, and through experience with related things. I hate being told to RTFM after I just went through the entire thing and have found nothing even related to my problem.
-- 'The' Lord and Master Bitman On High, Master Of All
14 hours of searching I can consider an exhausting search.
So it's really a question of 14 hours vs near instantaneous.
If you dont pick instantaneous you're merely a fucking idiot.
-- 'The' Lord and Master Bitman On High, Master Of All
I have a *far* easier time trying to find answers for linux. If a google search doesn't do it for me, there's almost always a mailing list I can join and talk ***directly to the developers*** There is nothing like that in the Windows world. I've also had much better luck finding code/programming examples for Linux. I recently was trying to work with Audio APIs in both OS's and had much better luck with Linux until I found some open source cross-platform code to use w/windows.
I'm not familar with the consumer IDE raid stuff although I've worked quite a bit with Compaq SmartArray controllers.
Infact, I have a Compaq Smart array SCSI RAID controller in both my PC's at home (desktop and server). They're available on ebay for very nice prices and are well supported by Linux.
The reason I mention it, is that I can pull all the disks out from one machine and pop them into the other - I don't even have to keep them in the same order! - and the controller is able to read the array configuration data from the disks and the logical volume(s) are immediately accessible. It's pretty sweet.
If it's just your RAID controller that's failed, try putting the disks into another machine with the same type of controller, or try replacing the controller. I'm not making any promises, but if it's a decent controller it should read the saved config data from the disks and make your logical volume available.
Have you tried the manufacturers tech support line? I'm sure they've delt with this situation before. I'm not trying to be a wiseass, but sometimes contacting the manufacturer is going to get you in touch with the folks who are most knowlegable about the product.
I'd rather be a conservative nutjob than a liberal with no nuts and no job.