Since upgrading to MacOS Sequoia I noticed backups of my machines that had a lot of small files were either taking an age or failing. I also noticed that large transfers would slow down significantly after a while.
After thinking this was an issue with my networking…and finding it wasn’t, I managed to narrow it down to Sequoia – the issue wasn’t experienced on previous versions of MacOS or Windows. How odd.
Anyway, this setting on the Synology NAS seems to resolve the issue:
Do not reserve disk space when creating files
To configure it, go into ‘Control Panel’ on the Synology, and select ‘File Services’:
From the ‘Advanced Settings’ menu, you want to select ‘Others’ at the top, and turn on ‘Do not reserve disk space when creating files’:
NOTE: This will reset the SMB Service so if you have any active connections they may disconnect and re-connect.
Anyway, after I’ve done that, those weird little problems seem to have gone away. For the more technically minded, there’s a description of what this does below:
strict allocate (S)
This is a boolean that controls the handling of disk space allocation in the server. When this is set to yes the server will change from UNIX behaviour of not committing real disk storage blocks when a file is extended to the Windows behaviour of actually forcing the disk system to allocate real storage blocks when a file is created or extended to be a given size. In UNIX terminology this means that Samba will stop creating sparse files.
This option is really designed for file systems that support fast allocation of large numbers of blocks such as extent-based file systems. On file systems that don’t support extents (most notably ext3) this can make Samba slower. When you work with large files over >100MB on file systems without extents you may even run into problems with clients running into timeouts.
When you have an extent based filesystem it’s likely that we can make use of unwritten extents which allows Samba to allocate even large amounts of space very fast and you will not see any timeout problems caused by strict allocate. With strict allocate in use you will also get much better out of quota messages in case you use quotas. Another advantage of activating this setting is that it will help to reduce file fragmentation.
To give you an idea on which filesystems this setting might currently be a good option for you: XFS, ext4, btrfs, ocfs2 on Linux and JFS2 on AIX support unwritten extents. On Filesystems that do not support it, preallocation is probably an expensive operation where you will see reduced performance and risk to let clients run into timeouts when creating large files. Examples are ext3, ZFS, HFS+ and most others, so be aware if you activate this setting on those filesystems.
Default: strict allocate = no
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