On Fri, 5 Dec 2014, Mike Snitzer wrote:
I do wonder what the performance impact is on this for dm. Have you tried a (worst case) test of writing blocks that are zero filled, but with the last byte not being a zero?
The additional overhead of worst-case should be (nearly) equal to the simplest test case of dd if=/dev/zero of=/dev/thinp/vol. In my testing that was 1.4GB/s within KVM on an Intel Xeon(R) CPU E3-1230 V2 @ 3.30GHz.
I could see where really fast storage that can obtain 1.4gb/s might notice a performance regression---but for most use cases that is quite fast.
-Eric
I haven't tested that yet, but I share your concern. Does fio offer the ability to slap down a specific pattern like this? If not is there a logical place to extend fio to enable this?
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