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Old 02-06-2019, 07:03 AM
d.r.h. d.r.h. is offline
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Join Date: Apr 2010
Location: NW Pennsylvania
Posts: 7
Some questions about backups on APFS formatted SSDs. Background: My main computer is a 3.6 GHz Intel Core i7 iMac with 32GB RAM and a 1TB SSD. I used to backup to two HFS+ formatted drives (a 750GB WD Scorpio Black, 7200 RPM - Daily, and a 500GB Hitachi, 5400 RPM - weekly). Both connected via USB3. I use a similar 500GB Hitachi for periodic backups on my Macbook pro (which has a 500GB internal SSD). I recently replaced the Hitachis with Otherworld Computing Electra 6G SSDs (a 1TB for the iMac and a 500GB for the MBP). Formatted both of these new SSDs APFS. After formatting, ran SD to do an erase and copy to the SSDs.

What confuses me is that my daily iMac smart backup to the new SSD ( going from SSD to SSD) is really not that much faster than to the WD Scorpio (maybe a minute faster ... in the 6 minute vs 7 minute range). I thought it would be much faster. This is not a big problem, as I would have still bought the SSDS. However, would really like to understand this.

Prior to doing a comparison test, I did a smart update on both so that they each would have a current clone of my iMac. I then used the computer for a while and then redid a smart update on each.

I did immediately notice one thing that was different when the backups started. When smart updating to the SSD, it took 30 seconds to create and mount a snapshot of the iMac ... where creating and mounting a snapshot smart updating the Scorpio is pretty much instantaneous. Here are snippets from my logs (backed up Scorpio first then immediately backed up the SSD):

Scorpio:

07:00:30 PM | Info | ...ACTION: Preparing NachalnikiMac snapshot
| 07:00:30 PM | Info | ......COMMAND => Creating Snapshot of NachalnikiMac
| 07:00:31 PM | Info | ......COMMAND => Mounting Snapshot for NachalnikiMac

SSD:

07:11:07 PM | Info | ...ACTION: Preparing NachalnikiMac snapshot
| 07:11:07 PM | Info | ......COMMAND => Creating Snapshot of NachalnikiMac
| 07:11:37 PM | Info | ......COMMAND => Mounting Snapshot for NachalnikiMac

I also ran a smart update on the Macbook Pro to check the time it took to create and mount a snapshot to the new SSD I use for that computer. It took 61 seconds:

10:52:53 AM | Info | ...ACTION: Preparing Nachalnik_MBP snapshot
| 10:52:53 AM | Info | ......COMMAND => Creating Snapshot of Nachalnik_MBP
| 10:53:54 AM | Info | ......COMMAND => Mounting Snapshot for Nachalnik_MBP


Here are the pertinent snippets from the logs showing the actual data evaluated and copied/cloned info:

Scorpio:

07:06:03 PM | Info | Evaluated 1077918 items occupying 151.85 GB (182758 directories, 875744 files, 19416 symlinks)
| 07:06:03 PM | Info | Copied 5341 items totaling 0.56 GB (180767 directories, 5325 files, 16 symlinks)
| 07:06:03 PM | Info | Cloned 146.05 GB of data in 331 seconds at an effective transfer rate of 441.23

SSD:

07:17:09 PM | Info | Evaluated 1077929 items occupying 151.85 GB (182763 directories, 875750 files, 19416 symlinks)
| 07:17:09 PM | Info | Copied 5222 items totaling 0.56 GB (710 directories, 5206 files, 16 symlinks)
| 07:17:09 PM | Info | Cloned 146.05 GB of data in 331 seconds at an effective transfer rate of 441.24

The time actually performing cloning on each and the effective transfer rate is just about the same, 331 seconds at around a 441 MB/s effective transfer rate.

Looking at the complete logs shows a very large number of actions performed by SD when copying to the SSD vs Scorpio which I assume are because of the format difference between the two. I assume this (along with the increased time to create and mount the snapshot) attributes to the overall amount of time SD takes to create the backup to the SSD. Also, not quite sure I understand the difference in the directories copied data info on the SSD vs Scorpio as recorded above:

Scorpio:

Copied 5341 items totaling 0.56 GB (180767 directories, 5325 files, 16 symlinks)

SSD:

Copied 5222 items totaling 0.56 GB (710 directories, 5206 files, 16 symlinks)

While this is all probably normal ... hoping you have some info that would help me understand why the overall time it takes to back up to a much faster SSD formatted to APFS is not that much different than to a somewhat fast regular HD formatted HFS+

Thanks.
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