On Sun, Oct 23, 2016 at 10:45 PM, David Turner <david.turner@xxxxxxxxxxxxxxxx> wrote:
1/3 of your raw data on the osds will be deleted and then it move a bunch around. I haven't done it personally, but I would guess somewhere in the range of 50-70% data movement. It will depend on how many pgs you have, failure domains (hosts by default), etc.
Maybe I'm seriously misremembering how this works, but I would not expect any data movement solely as the result of a pool reducing its size (replica count). Everything will have to re-peer but otherwise it should just remove OSDs from the up/acting sets.
Obviously *increasing* the size means you'll have to re-replicate and that will do all kinds of things, but it still won't be a rebalance — just lots and lots of data being sent across the network to up the replica counts.
-Greg
Sent from my iPhone
> On Oct 23, 2016, at 9:56 AM, Sebastian Köhler <sk@xxxxxxxxx> wrote:
>
> Thanks for the help, is there any information available on how much data
> movement will happen when I reduce the size from 3 to 2? The min_size is
> already at 1.
>
>> On 10/23/2016 05:43 PM, David Turner wrote:
>> Make sure to also adjust your min_size. Having those be the same number
>> can cause issues if and when you lose an osd from your cluster.
>>
>> Like Wido said, you can change the size of a replica pool at any time,
>> it will just cause a lot of data to move.
>>
>> Sent from my iPhone
>>
>>> On Oct 23, 2016, at 4:30 AM, Wido den Hollander <wido@xxxxxxxx> wrote:
>>>
>>>
>>>> Op 23 oktober 2016 om 10:04 schreef Sebastian Köhler <sk@xxxxxxxxx>:
>>>>
>>>>
>>>> Hello,
>>>>
>>>> is it possible to reduce the replica count of a pool that already
>>>> contains data? If it is possible how much load will a change in the
>>>> replica size cause? I am guessing it will do a rebalance.
>>>>
>>>
>>> Yes, just change the 'size' parameter of the pool. Data will rebalance
>> indeed if you increase the number.
>>>
>>> Wido
>>>
>>>> Thanks
>>>>
>>>> Sebastian
>>>>
>>>>
>>
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