zfs discuss - Nov 2007 - Expanding a Harware RAID 5 Array vdev in ZFS?

I have searched high and low and cannot find the answer. I read about how zfs
uses a Device ID for identification, usually provided by the firmware of the
device. So if an controller presents an (array) lun w/a unique device ID, what
would happen if I onlined the pool, and suddenly that lun was twice the size? Or
would the controller present a different ID because the array characteristics
have changed? All the same data would be contained within the vdev, including
pool metadata, just spread across more drives... It may be a dealbreaker, and I
REALLY would like to use zfs. Can it be done?

Thanks!!
 
 
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On Nov 28, 2007 12:58 AM, Justin Tuttle <kill_bill_gates8 at hotmail.com>
wrote:
> I have searched high and low and cannot find the answer. I read about how
zfs uses a Device ID for identification, usually provided by the firmware of the
device. So if an controller presents an (array) lun w/a unique device ID, what
would happen if I onlined the pool, and suddenly that lun was twice the size? Or
would the controller present a different ID because the array characteristics
have changed? All the same data would be contained within the vdev, including
pool metadata, just spread across more drives... It may be a dealbreaker, and I
REALLY would like to use zfs. Can it be done?
Your array should keep on using the same HW ID, since you would rather
"grow" the LUN, than re-create a bigger one.

Many months ago I tried to get Solaris to recognize a bigger LUN after
the initial branding... but I couldn''t get it to work correctly.

I do know that there has been work done in this area of "auto LUN
resizing" ... but I don''t know what the status is.

Thanks for the response. I don''t know enough about the symantics of the
device IDs, I hope it does not change, and that maybe zfs will see that the lun
has grown. Seeing if you can use use a file system or file as a vdev (and
can''t they change sizes?) then you''d figure it could do the
same with an array vdev. Especially since zfs is touted as
''dynamic'' everything (unless, of course, you want to shrink a
pool)...I will try to test it see what happens, I just have to find somewhere to
stash another 400GB to clear off another drive in the mean time. If anyone has
definitive knowledge and can save me the trouble, please chime in. Thanks.
 
 
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