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
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This archive was generated by hypermail 2b29 : Sat Nov 23 2002 - 22:00:34 EST