One Mac client very slow. Fusion drive the cause?

[pjreagan]

Two very similar client computers, backing up to the same Retrospect Server on the same network, have very different backup performance rates.  So far the only apparent difference is that the slow one has a Fusion drive.  Could this be causing the slowness?

                           "AG-04"                        "DD-13"
From Script Log of completed backups...
copy                   1,483 MB/min               607 MB/min
compare            2,742 MB/min            1,364 MB/min

Machine Comparison...
drive type            HD                               Fusion
macOS                10.13.6 High Sierra  10.13.6 High Sierra
format                 Apple_HFS                 Apple_HFS
network               1 Gb/sec                    1 Gb/sec
Instant Scan       enabled                      enabled
client version      16.5.1 (104)              16.5.1 (104)

From Retrospect Server v16.6.0 (114), my "DD-14"...
ping to                  0.496 ms                   0.459 ms

Script...
security                password only           password only
block level inc.    off                                off
byte-by-byte         off                                off
data comp.          off                                 off
bup started          with script                   with script

 

 

[DavidHertzberg]

pjreagan,

How about the comparative number of files backed up, vs. the total bytes?  Lots of smaller files means a slower backup and compare than fewer larger files.

If there's a significant difference in the processor speeds between "AG-04" and "DD-13", that will also affect the Retrospect "client" backup speeds. 

This post in a 2017 thread, especially the first two paragraphs (the P.S. mostly rules out speed of the "backup server" for "client" files), covers the first part of experiments I ended up doing that have a bearing on this.  This post in that same thread,  and the one following, covers the rest.   This post near the end of the same thread discusses my hypothesis on slowness of "client" backups.

P.S.: This ArsTechnica Mac forum post says "My 2012 Era iMac with 1Tb Fusion Drive is starting to really slow down. It seems like when the drive is nearly full, the physical drive doesn't like to spin up anymore. ugh."