Hi I've got the same problem. Very slow restore process, it's take almost 11 hours. Please suggest.
restore vma archive: zstd -q -d -c /var/lib/vz/dump/vzdump-qemu-100-2020_09_21-20_16_08.vma.zst | vma extract -v -r /var/tmp/vzdumptmp5015.fifo - /var/tmp/vzdumptmp5015
CFG: size: 577 name: qemu-server.conf
DEV: dev_id=1 size: 214748364800 devname: drive-scsi0
DEV: dev_id=2 size: 322122547200 devname: drive-scsi1
CTIME: Mon Sep 21 20:16:09 2020
Logical volume "vm-100-disk-0" created.
new volume ID is 'local-lvm:vm-100-disk-0'
Logical volume "vm-100-disk-1" created.
new volume ID is 'local-lvm:vm-100-disk-1'
map 'drive-scsi0' to '/dev/pve/vm-100-disk-0' (write zeros = 0)
map 'drive-scsi1' to '/dev/pve/vm-100-disk-1' (write zeros = 0)
progress 1% (read 5368709120 bytes, duration 589 sec)
progress 2% (read 10737418240 bytes, duration 2100 sec)
progress 3% (read 16106127360 bytes, duration 2761 sec)
progress 4% (read 21474836480 bytes, duration 2811 sec)
progress 5% (read 26843545600 bytes, duration 2811 sec)
progress 6% (read 32212254720 bytes, duration 2812 sec)
progress 7% (read 37580963840 bytes, duration 2812 sec)
progress 8% (read 42949672960 bytes, duration 2833 sec)
progress 9% (read 48318382080 bytes, duration 2949 sec)
progress 10% (read 53687091200 bytes, duration 2949 sec)
progress 11% (read 59055800320 bytes, duration 2984 sec)
progress 12% (read 64424509440 bytes, duration 2984 sec)
progress 13% (read 69793218560 bytes, duration 2984 sec)
progress 14% (read 75161927680 bytes, duration 2984 sec)
progress 15% (read 80530636800 bytes, duration 2985 sec)
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progress 22% (read 118111600640 bytes, duration 3675 sec)
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progress 25% (read 134217728000 bytes, duration 3927 sec)
progress 26% (read 139586437120 bytes, duration 6700 sec)
progress 27% (read 144955146240 bytes, duration 9380 sec)
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progress 30% (read 161061273600 bytes, duration 16850 sec)
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progress 35% (read 187904819200 bytes, duration 19253 sec)
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progress 45% (read 241591910400 bytes, duration 31937 sec)
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progress 47% (read 252329328640 bytes, duration 32696 sec)
progress 48% (read 257698037760 bytes, duration 32696 sec)
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progress 50% (read 268435456000 bytes, duration 32704 sec)
progress 51% (read 273804165120 bytes, duration 32749 sec)
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progress 53% (read 284541583360 bytes, duration 32750 sec)
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progress 59% (read 316753838080 bytes, duration 32824 sec)
progress 60% (read 322122547200 bytes, duration 32863 sec)
progress 61% (read 327491256320 bytes, duration 32908 sec)
progress 62% (read 332859965440 bytes, duration 33216 sec)
progress 63% (read 338228674560 bytes, duration 33354 sec)
progress 64% (read 343597383680 bytes, duration 33375 sec)
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progress 72% (read 386547056640 bytes, duration 33911 sec)
progress 73% (read 391915765760 bytes, duration 33917 sec)
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progress 76% (read 408021893120 bytes, duration 34090 sec)
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progress 86% (read 461708984320 bytes, duration 34093 sec)
progress 87% (read 467077693440 bytes, duration 34129 sec)
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progress 91% (read 488552529920 bytes, duration 34290 sec)
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progress 95% (read 510027366400 bytes, duration 34296 sec)
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progress 97% (read 520764784640 bytes, duration 34319 sec)
progress 98% (read 526133493760 bytes, duration 34319 sec)
progress 99% (read 531502202880 bytes, duration 34319 sec)
progress 100% (read 536870912000 bytes, duration 34319 sec)
total bytes read 536870912000, sparse bytes 468128428032 (87.2%)
space reduction due to 4K zero blocks 1.33%
rescan volumes...
TASK OK