why should I "initialize" JBOD disks?

Hi,

I just installed an Adaptec SAS 4805 and plugged 8 disks previously used
"as is" (no raid) on an LSI adapter but none are recongnized as boot
disk ("no bios installed").

It seems I need to "initialize" (read: wipe) them in the Adaptec bios
menu before being able to use them as JBOD.

What the fuck?!

By my defintion JBOD should means "just get out of the way and let me
use my disks as they are".

Does that "initlialization" mean that disks become unusable when plugged
to an adapter of any other brand or model?

What is the underlying format of JBOD disks. Can they be read by a
straight, non-raid adapter?

These hardware raid cards suck on so many levels...


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Re: why should I "initialize" JBOD disks?

On Fri, 20 May 2011, Louis-David Mitterrand wrote:

> Hi,
>
> I just installed an Adaptec SAS 4805 and plugged 8 disks previously used
> "as is" (no raid) on an LSI adapter but none are recongnized as boot
> disk ("no bios installed").
>
> It seems I need to "initialize" (read: wipe) them in the Adaptec bios
> menu before being able to use them as JBOD.
>
> What the fuck?!
>
> By my defintion JBOD should means "just get out of the way and let me
> use my disks as they are".
>
> Does that "initlialization" mean that disks become unusable when plugged
> to an adapter of any other brand or model?
>
> What is the underlying format of JBOD disks. Can they be read by a
> straight, non-raid adapter?
>
> These hardware raid cards suck on so many levels...

Yup.

I don't know about that, but I had something similar with a Dell
controller - I wanted a box of 15 x 500GB drives - but the only way to get
it was to buy it with their PERC RAID controller cards, however I was
assured that I didn't need to use the card RAID functions and I could use
them "just as a box of disks" ...

It wasn't having it and in the end, I had to create 15 RAID-0 arrays of
one disk each, which I could them assemble as a RAID-6 drive underLinux
MD.

It worked fine, but would have been a PITA to anyone else changing a drive
(fortunately it never broke in it's lifetime) but the down-side was that
the controler hid all the SMART information from the host )-:

Bah!

Gordon
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Re: why should I "initialize" JBOD disks?

----- Message from vindex+lists-linux-raid@apartia.org ---------
Date: Fri, 20 May 2011 15:32:44 +0200
From: Louis-David Mitterrand
Subject: why should I "initialize" JBOD disks?
To: linux-raid@vger.kernel.org


> Hi,
>
> I just installed an Adaptec SAS 4805 and plugged 8 disks previously used
> "as is" (no raid) on an LSI adapter but none are recongnized as boot
> disk ("no bios installed").
>
> It seems I need to "initialize" (read: wipe) them in the Adaptec bios
> menu before being able to use them as JBOD.
>
> What the fuck?!

The controller puts the configuration details for the disk on the disk
itself. That way you can plug the disk into another port or controller
of the same brand and it will simply work.

> By my defintion JBOD should means "just get out of the way and let me
> use my disks as they are".
>
> Does that "initlialization" mean that disks become unusable when plugged
> to an adapter of any other brand or model?

It will show as uninitialized.

> What is the underlying format of JBOD disks. Can they be read by a
> straight, non-raid adapter?

The configuration needs to be stored somewhere on the disk. Either at
the beginning or at the end (or a combination of both).
Hence I would expect the start of the disk to be shifted a bit (what
used to be block 0 on the disk while plugged into the RAID controller
will be some higher block) or the disk will "end" a bit before the
actual end of the disk.
So I'm pretty sure you can dd such a disk onto another one to rescue
the data given the right seek offset.
Alex.

----- End message from vindex+lists-linux-raid@apartia.org -----



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