Mailinglist Archive: opensuse (1606 mails)

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Re: [opensuse] Recover md RAID-1.

----- Original Message -----
From: "Andrew Joakimsen" <joakimsen@xxxxxxxxx>
To: "Lars Marowsky-Bree" <lmb@xxxxxxx>
Cc: <opensuse@xxxxxxxxxxxx>
Sent: Monday, September 01, 2008 10:13 AM
Subject: Re: [opensuse] Recover md RAID-1.


* Reinstall OS on first drive drive (screw this md raid stuff... no
--force does not work... obviously md RAID is worthless)

Funny it works great for me and I have run into hairier problems than you
Involving for instance raid0 arrays with one or more bad drives, raid5 arrays
with more than one bad drive, and was able to reasssemble and mount at least
well enough to recover data. Sometimes it meant actually destroying and
re-creating the raid metadata to mak the payload data _appear_ uncorrupt again,
where I just had to realize that some of the data was in fact corrupt or maybe
it wasn't, in one case the disk had a physically bad spot, but it was on spot
that was actually unused by any files, just it was within an array and within a
filesystem, causing both to be broken, but, cloning the disk with dd_rescue
onto a new disk that was physically all good, allowed me to re-create a new
raid structure and repair the filesystem while managing to preserve the files.

I could not have done that purely by the info provided in the man page for
mdadm, and no easy magic front-end exists either that I know of (unless you
count paying a consultant), but, googling for other peoples experiences, and
mostly a lot of experimentation on test disks and test data showed me in more
detail what exactly some of the things really mean that are mentioned but not
explained in the man pages, and showed me what exactly certain commands &
actions would do in certain situations. After *that* I was able to make md raid
do not only anything I wanted, but even more than what the expensive and easy
to use hardware raid cards can do (except for the one unavoidable particular
hardware feature of making an array appear to be a plain disk to the
motherboard bios). Rather the opposite of worthless. For starters, it's worth
far more than the time & effort it takes to learn how to use it.

So, if you don't want to put in that time learning how to use something, then
yes indeed you should not use it.

Brian K. White brian@xxxxxxxxx
filePro BBx Linux SCO FreeBSD #callahans Satriani Filk!

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