Am Sonntag, 7. Februar 2016, 21:07:13 CET schrieb Kai Krakow: > Am Sun, 07 Feb 2016 11:06:58 -0800 > > schrieb Nikolaus Rath <nikol...@rath.org>: > > Hello, > > > > I have a large home directory on a spinning disk that I regularly > > synchronize between different computers using unison. That takes ages, > > even though the amount of changed files is typically small. I suspect > > most if the time is spend walking through the file system and checking > > mtimes. > > > > So I was wondering if I could possibly speed-up this operation by > > storing all btrfs metadata on a fast, SSD drive. It seems that > > mkfs.btrfs allows me to put the metadata in raid1 or dup mode, and the > > file contents in single mode. However, I could not find a way to tell > > btrfs to use a device *only* for metadata. Is there a way to do that? > > > > Also, what is the difference between using "dup" and "raid1" for the > > metadata? > > You may want to try bcache. It will speedup random access which is > probably the main cause for your slow sync. Unfortunately it requires > you to reformat your btrfs partitions to add a bcache superblock. But > it's worth the efforts. > > I use a nightly rsync to USB3 disk, and bcache reduced it from 5+ hours > to typically 1.5-3 depending on how much data changed.
An alternative is using dm-cache, I think it doesn´t need to recreate the filesystem. I wonder what happened to the VFS hot data tracking stuff patchset floating around here quite some time ago. -- Martin -- 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
