On Fri, Apr 30, 2021 at 7:56 PM Roger Heflin <rogerhef...@gmail.com> wrote:
> 388217 * 10ms = about 3800 seconds to read that file or about > 26MB/sec, but with all of the seeks most of that time will be idle > time waiting on disk (iowait), and it is very possible that parts of > the file have large extents and other parts of the file are horribly > fragmented. And that ignores any time to do any other work related to > the rsync and file io. How long does it take to copy the file? > Not sure, I don't make a habit of moving 100GB files around too often :) > btrfs has an autodefrag mount option, no idea how good or bad it > works, but it might be able to reduce the extents given enough time to > a reasonable number and keep it under control. > Doing a forced defragment now specifically on the file and it's taking a while. so long as you are using rsync to read the file the fact that the db > is cow is probably not an issue (since from rsync's point of view it > is just one big file). if you have small writes to the file and > btrfs was set to cow that would make a mess. Not sure for a db btrfs > is a good filesystem choice on a spinning disk, disabling cow might > have mostly fixed this. it not clear to me that if you set the defrag > option now if it will fix the already fragmented parts of the file or > not. And if you turned off cow later the file may have already been > heavily fragemented. I'm not specifically accessing the file, the Monero daemon is so no rsync involved as far as I know. I have already set the directory containing the file as nodatacow and moved the file to ensure it was set previously. Thanks, Richard
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