New Disk Utility apparently not using rdisk when saving / restoring partitions
New Disk Utility apparently not using rdisk when saving / restoring partitions
- Subject: New Disk Utility apparently not using rdisk when saving / restoring partitions
- From: Thomas Tempelmann <email@hidden>
- Date: Fri, 31 Mar 2017 23:51:18 +0200
Not relly a file system related thing, but since I'm tired of filing bug with Apple's bugreporter and mostly just getting red tape thrown at me, I thought I bring it up here in case someone listens and wants to take reponsibility:
I found that, when using the new DU, using the Restore operation to copy a partition from one drive to another, it's unusually slow. Comparing similar operations in Terminal using the "dd" command makes me believe that DU is using /dev/diskN to read and write, whereas it should be using /dev/rdisk.
The speed difference is substantial: I had wanted to copy a 750 GB SSD from one MacBook Pro, connected via Thunderbolt Target Disk Mode to another MBP with a 1 TB SDD. With Sierra's DU (loaded from the Recovery partition) as well as with "dd" using "disk", this went along at about with less than 40 MB/s. Performing the same with "dd" and "rdisk", I got to the maximum, which was about 200 MB/s. That's more than five times slower than it should be.
I'm going to write a blog article about this over the weekend, too.
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