Open Stack

On 3 Mar 2016, at 13:32, Mark Kirkwood wrote:

> On 03/03/16 03:57, Peter Brouwer wrote:
>> Hello
>>
>> I am trying to find some information on the relationship of the ring
>> (builder) structure of swift and the size of disks used, i.e. how is
>> capacity of a disk managed.
>> I've seen many docs/blogs explaining the ring and partitions but I have
>> not seen any info on how available space per disk is managed, i.e. the
>> relationship between disk size and allocating ring partitions.
>>
>> Do all disks in a ring need to be of the same capacity? If not how is
>> swift handling the amount of free space?
>>
>> Any pointers to documentation on this?
>>
>
> You specify a weight for each device that is added to the ring, this
> lets you cope with different sized disks e.g:
>
> Suppose sdb is 1TB and sdc 500GB
>
> $ swift-ring-builder object.builder add r1z1-192.168.122.21:6000/sdb 1
> $ swift-ring-builder object.builder add r1z1-192.168.122.21:6000/sdc 0.5


One easy way to manage ring weights is to use the number of GB on the drive. So a 1TB drive is 1000, a 500Gb drive is 500, and an 8TB drive is 8000. Makes thinking about it easier, at least to me.

The actual weight doesn't matter by itself. It only matters compared to all the other weights in the ring.


--John




>
> Cheers
>
> Mark
>
>
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