Very slow mounting & access of encrypted sparse bundles - unsupported Macbook

[cinergi]

Hello,

I upgraded my (officially unsupported) Macbook 5,1 from El Capitan to Sierra yesterday using dosdude1's excellent patch utility. All went well and Sierra seems to be working fine, except for one problem: mounting encrypted .sparsebundle disk images is now very slow - it required approximately 15 minutes for a ~10GB image before it was accessible in the Finder. During this time, the CPU was pegged at 100%.

After the image finally mounted, working with the files within it (loading, saving, etc.) also seems significantly slower than before. I never had any issues with spare bundles (including this specific one) in El Capitan. I don't know whether it has anything to do with Sierra not being officially supported on my Macbook, although everything else seems to be working perfectly.

Any ideas?

Thanks
cinergi

 

[cinergi]

In case anyone else runs into this problem, I traced it to my antivirus Sophos. It is misbehaving in Sierra: its scan process goes to 100% CPU usage whenever any sparse bundle is mounted. Even creating a new empty sparse bundle in Disk Utility triggers this issue.

I've switched to Avast, and the problem is gone.

cinergi