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Hi John, 

Thanks a lot for your response. I was looking at two specific use cases- 1) Volume attached to an instance 2) Volume not attached to any instance. I am assuming in both cases Cinder creates a new volume at the target and copies data from the source volume to the target volume. In the second case, re-mounting, re-attaching to the instance is manual since the target volume gets a different id..  correct? 

Thanks!
Narendra

-----Original Message-----
From: John Griffith [mailto:john.griffith at solidfire.com] 
Sent: Tuesday, November 12, 2013 11:48 AM
To: Trivedi, Narendra
Cc: openstack at lists.openstack.org
Subject: Re: [Openstack] Cinde muti-backend feature

On Tue, Nov 12, 2013 at 10:24 AM, Trivedi, Narendra <Narendra.Trivedi at savvis.com> wrote:
> Hi All,
>
>
>
> Could someone please explain the Cinder multi-backends feature (as of 
> Havana)? Specifically, I had the following questions:
>
>
>
> 1)      Can I attach multiple physical storage backends (let's say one all
> SSD, another all SATA for instance) to a single host?
>
> 2)      How does migration between different multiple backends work? Let's
> say the an SSD volume is attached to a VM I want to migrate all the 
> data in the SSD volume to a SATA volume without bringing down the 
> interface. Do I have to manually mount/un-mount the persistent volume 
> to the instance- how do paths are maintained? For instance, let's say 
> the persistent volume was /dev/vdx mounted to /mnt/vol0 , how does it re-appear ?
>
>
>
> Thanks a lot in advance!
>
> Narendra
>
>
>
>
>
>
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Hi Narendra,

Yes, the whole point is in fact that you can have multiple physical backends controlled by a single host.  Of course it still needs to be a cinder supported backend/driver.  To configure this you can check out the following link [1].

With respect to the migration, you should be able to run "migrate <volume-id> <host>", where host is the hostname of the backend you want to migrate too.

John

[1] https://wiki.openstack.org/wiki/Cinder-multi-backend

This message contains information which may be confidential and/or privileged. Unless you are the intended recipient (or authorized to receive for the intended recipient), you may not read, use, copy or disclose to anyone the message or any information contained in the message. If you have received the message in error, please advise the sender by reply e-mail and delete the message and any attachment(s) thereto without retaining any copies.