[dm-devel] dm-thin
Zdenek Kabelac
zkabelac at redhat.com
Tue Oct 21 09:32:54 UTC 2014
Dne 21.10.2014 v 03:36 lilofile napsal(a):
> In dm-thin.c,
> /*
> * The block size of the device holding pool data must be
> * between 64KB and 1GB.
> */
> #define DATA_DEV_BLOCK_SIZE_MIN_SECTORS (64 * 1024 >> SECTOR_SHIFT)
> #define DATA_DEV_BLOCK_SIZE_MAX_SECTORS (1024 * 1024 * 1024 >> SECTOR_SHIFT)
>
> why the block size must be between 64KB and 1GB, can I change the value of DATA_DEV_BLOCK_SIZE_MIN_SECTORS? what effect if the value of DATA_DEV_BLOCK_SIZE_MIN_SECTORS<128?
Performance reasons mainly - updating metadata much more frequently is
lowering the throughput considerable.
The other issue is you would also scale up required metadata size.
Zdenek
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