Some more data points, observations, and questions. For each test, I'd --create the array, drop the caches, --grow, and then watch vmstat and also record the time between kernel: md: resuming resync of md99 from checkpoint. and kernel: md: md99: resync done. I found two things: 1. metadata version matters. Why? 2. VERY LITTLE I/O takes place (between 0 and 100KB/s, typically no I/O at all) according to vmstat. Why? If it takes 1m34s to "grow" the array, but no I/O is taking place, then what is actually taking so long? 3. I removed the bitmap for these tests. Having a bitmap meant that the overall speed was REALLY HORRIBLE. The results: metadata: time taken 0.9: 27s 1.0: 27s 1.1: 37s 1.2: 1m34s Questions (repeated): 1. Why does the metadata version matter so much? 2. If no I/O is taking place, why does it take so long? [ NOTE: I/O must be taking place but why doesn't vmstat show it? ] -- Jon -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
