lkml.org 
[lkml]   [2002]   [Nov]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: RFC - new raid superblock layout for md driver
On Wednesday November 20, sdake@mvista.com wrote:
> Neil,
>
> I would suggest adding a 64 bit field called "unique_identifier" to the
> per-device structure. This would allow a RAID volume to be locked to a
> specific host, allowing the ability for true multihost operation.

You seem to want a uniq id in 'per device' which will identify the
'volume'.
That doesn't make sense to me so maybe I am missing something.
If you want to identify the 'volume', you put some sort of id in the
'per-volume' data structure.

This is what the 'name' field is for.

>
> For FibreChannel, we have a patch which places the host's FC WWN into
> the superblock structure, and only allows importing an array disk (via
> ioctl or autostart) if the superblock's WWN matches the target dev_t's
> host fibrechannel WWN. We also use this for environments where slots
> are used to house either CPU or disks and lock a RAID array to a
> specific cpu slot. WWNs are 64 bit, which is why I suggest such a large
> bitsize for this field. This really helps in hotswap environments where
> a CPU blade is replaced and should use the same disk, but the disk
> naming may have changed between reboots.
>
> This could be done without this field, but then the RAID arrays could be
> started unintentionally by the wrong host. Imagine a host starting the
> wrong RAID array while it has been already started by some other party
> (forcing a rebuild) ugh!

Put your 64 bit WWN in the 'name' field, and teach user-space to match
'name' to FC adapter.

Does that work for you?

NeilBrown
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:31    [W:0.341 / U:0.596 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site