[dm-devel] Writes going to source device in write-back mode

[BK, GirishKumar]

Hi,

I have observed (via iostat) dm-cache is writing to source device also in write back mode (equivalent to IOS going to cache device) even though cache is filled with 25% cache size.

Any explanation as to why this behavior when it is expected that none of the IOS (random 4 K writes) should be going to source device in write back mode?

Thanks,
#Girish_BK

Here are test parameters:
RHEL: 7.0 (3.19 kernel)
Dm-cache policy set to 'write back' and cache block size set to 32K.

0 16384000 cache 8 637/2048000 64 17/256000 189 84 84 524204 0 17 0 1 writeback 2 migration_threshold 2048 mq 10 random_threshold 4 sequential_threshold 512 discard_promote_adjustment 1 read_promote_adjustment 4 write_promote_adjustment 8

Test run was with fio: Random 4K write (100%)



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