Re: backup_calculate_cluster_size does not consider source

[Stefan Hajnoczi]

On Tue, Nov 05, 2019 at 11:02:44AM +0100, Dietmar Maurer wrote:
> Example: Backup from ceph disk (rbd_cache=false) to local disk:
> 
> backup_calculate_cluster_size returns 64K (correct for my local .raw image)
> 
> Then the backup job starts to read 64K blocks from ceph.
> 
> But ceph always reads 4M block, so this is incredibly slow and produces
> way too much network traffic.
> 
> Why does backup_calculate_cluster_size does not consider the block size from
> the source disk? 
> 
> cluster_size = MAX(block_size_source, block_size_target)

CCing block maintainers so they see your email and you get a response
more quickly.

Stefan

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