Hi Hugo, For the use case I'm looking for I'm interested in having snapshot(s) open at all time. Imagine for example snapshot being created every hour and several of these snapshots kept at all time providing quick recovery points to the state of 1,2,3 hours ago. In such case (as I think you also describe) nodatacow does not provide any advantage.
I have not seen autodefrag helping much but I will try again. Is there any autodefrag documentation available about how is it expected to work and if it can be tuned in any way I noticed remounting already fragmented filesystem with autodefrag and putting workload which does more fragmentation does not seem to improve over time > Well, nodatacow will still allow snapshots to work, but it also > allows the data to fragment. Each snapshot made will cause subsequent > writes to shared areas to be CoWed once (and then it reverts to > unshared and nodatacow again). > > There's another approach which might be worth testing, which is to > use autodefrag. This will increase data write I/O, because where you > have one or more small writes in a region, it will also read and write > the data in a small neghbourhood around those writes, so the > fragmentation is reduced. This will improve subsequent read > performance. > > I could also suggest getting the latest kernel you can -- 16.04 is > already getting on for a year old, and there may be performance > improvements in upstream kernels which affect your workload. There's > an Ubuntu kernel PPA you can use to get the new kernels without too > much pain. -- Peter Zaitsev, CEO, Percona Tel: +1 888 401 3401 ext 7360 Skype: peter_zaitsev -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
