Rich Freeman wrote: > On Mon, Aug 3, 2020 at 1:30 AM Dale <rdalek1...@gmail.com> wrote: >> Little update here. Rich, I think you mentioned it would slow down when it >> ran out of PMR space while trying to redo the shingled part. Up until now, >> I hadn't ran into that issue. It seems the PMR section for this drive is >> somewhere around 40 or 50GBs, maybe 60GBs. I hadn't had time for backups in >> over a week so it was a good bit larger than usual. It was around 70GBs, >> maybe 75. When it got close to the end of the rsync process, I noticed it >> slowed down quite a bit. I'd guess about half or so. Usually it runs at >> around 180 to 190MBs/sec for larger files. Pretty close to the end, rsync >> was showing around 100MBs/sec at best. It was a little over on some but >> mostly a little below that. Earlier in the process, it was the normal speed. > I doubt this particular drop is the result of SMR, assuming 100MB/s is > the instantaneous speed. 100MB/s is still reasonable for a hard drive > - on newer CMR drives I've seen the speed of dd drop from 200MB/s to > 100MB/s for sequential writes as the heads move from one end of the > drive to the other, and then it goes back up to 200MB/s if you start > over at the beginning (badblocks testing and so on). > > That level of drop is probably more likely to be due to filesystem > overhead and so on - fragmentation/etc. When SMR buffer overrun > occurs you REALLY hit a wall and the rates drop quite a bit more than > that. If it were a difference of only 50% most would probably > tolerate it. > > Now, if 100MB/s were an updating average across the entire run then > that would be a different matter, because that would mean that it was > running at 200MB/s for most of the run, and then probably dropping > much closer to 0 for a while so as to drive the overall average down > to 100MB/s. I'm not sure where you're getting those numbers from so I > don't know what period that 100MB/s reflects. For an instantaneous > speed I'd consider it a completely reasonable performance for a > typical hard drive when you're writing to a filesystem. If you were > using dd or maybe copies of very large files on an efficient > filesystem you would get better results. >
I use the --progress option with rsync. It shows the copy speed, elapsed time etc for each file. Some files are small and the speed it shows isn't accurate at all because the files are just to tiny to get a accurate measure. I ignore that info on the smaller files. Videos however are larger files and sometimes can take a lot longer to copy over. Those tend to be more accurate. Anyway, that is where the numbers came from. I wish I had saved the output but sadly I had finished my OS updates and needed to logout and back in again. In the past, I've never seen the drive on the larger files be that slow even toward the end. Generally, it stays pretty close to 180MBs/sec or so which is what I usually get with PMR drives. Of course, the PMR drives don't keep doing the bumpy thing for a while when it is done either. Maybe it is something else but it sure did the bumpy thing a lot longer this time. Either way, just wanted to update that a large copy made it slow down. Other than the initial copy, this is the largest rsync I've ever done to that drive. Most are around 20, maybe 25GBs. Dale :-) :-)
