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Yes, that's true. If Swift can't find the primary location for data on a write, it will put the data on a handoff node. Later, when the primary is available (or in this case, the IP is updated in the ring), the data will be moved back. To be explicit, this is new data put during the window between the change in IP and the ring update.

This window is another reason dynamic IPs are much harder to use in a Swift cluster.

--John





On Aug 18, 2014, at 12:10 PM, Luse, Paul E <paul.e.luse at intel.com> wrote:

> Don't you also have the issue of having those nodes unavailable during the time when their IP changes and someone gets around to updating and re-propagating those rings right?  Depending on the size of that window and how much traffic is going on at the time you may very well end up with a lot of extra data movement as incoming data makes it to handoffs (assuming their  addresses didn't change) and then back again after the rings reflect the new addresses of the primary(ies).  
> 
> -Paul
> 
> -----Original Message-----
> From: John Dickinson [mailto:me at not.mn] 
> Sent: Monday, August 18, 2014 11:54 AM
> To: Jyoti Ranjan
> Cc: openstack at lists.openstack.org
> Subject: Re: [Openstack] [Swift] IP address of Swift nodes : need help
> 
> If the IP for a storage node changes, you'll need to update the rings where that server's drives are. You can update the IP with the `swift-ring-builder set_info ...` command and then use "write_ring" to serialize it. Doing this will not cause any data movement in the cluster. Removing the server and re-adding it to the ring will cause data movement.
> 
> So, no, it's not strictly necessary to use static IPs. You'll be saving yourself some management overhead if you do, though.
> 
> --John
> 
> 
> 
> 
> On Aug 18, 2014, at 11:42 AM, Jyoti Ranjan <jranjan at gmail.com> wrote:
> 
>> Hi,
>> 
>> We are deploying Swift clusters where we do have IP addresses assigned to Swift nodes via DHCP. Curious to know, what will happen if IP address of a give node change that node is made part of Swift cluster. For e.g. let us assume that Swift object node got IP 192.168.10.2 and later it changes to 192.168.10.9 because of DHCP. Will running Swift cluster get affected?
>> 
>> In other words, is it necessary to use static IP for Swift nodes?
>> 
>> 
>> Regards,
>> Jyoti Ranjan
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