Case sensitive volume on Mac is very slow

Question

I created a case sensitive volume on my Macbook Pro with this command:

hdiutil create -type UDIF -fs 'Case-sensitive Journaled HFS+' -size 200g -volname Unix ~/Unix

I see that volume performance is much worse than writing to the disk directly, see:

9801a7953161% sync; /bin/dd if=/dev/zero of=/Volumes/Unix/some_file bs=1m count=10240; sync
10240+0 records in
10240+0 records out
10737418240 bytes transferred in 63.777882 secs (168356457 bytes/sec)
9801a7953161% sync; /bin/dd if=/dev/zero of=/Users/XXX/some_file bs=1m count=10240; sync
10240+0 records in
10240+0 records out
10737418240 bytes transferred in 8.968688 secs (1197211702 bytes/sec)

Any idea what's wrong here? I ran first aid on my disk - no issues found.

Answer 1

I’ve seen some performance improvements by turning off access time on the volume. The command to do that:

mount -vuwo noatime /Volumes/[volume name]

More details can be found in this article titled, “OS X - Setting No-Access-Time on OS X SSD Volumes.”

And when you partition a volume as APFS, you can add a new partition to the existing disk that is case sensitive. There is little to no performance impact.