Slow backup, probably slow disk?

Virtualmin
1
SYSTEM INFORMATION
OS type and version rocky linux 9 amd64
Webmin version 2.105
Virtualmin version 7.9.0
Related packages scheduled backups

Hello, i changed my server with a new server.
works all good with migration of virtual server from old to new.
problem is only backup duration…

i try to backup about 400GB,
i have a remote server with 200mbps dedicated.
if i try to upload a single file with ssh i can reach 200mbps every time…

if i plan a scheduled backup with default tar+gzip , take about 21 hours to complete…
if i plan zip , take about 9 hours
if i plan tar, take about 4 hours 30 minutes…
i try to upload and mount sshfs to backup direct to remote server (same behaviour)

so i’m sure is not bandwith because i have dedicated band and with tar works fine.

may be a speed of disk? to zip/bzip/compress file is slow to read or write???

i test my storage with
dd if=/dev/zero of=/dd_test bs=1MB count=64 conv=fdatasync
64000000 bytes (64 MB, 61 MiB) copied, 0.13984 s, 458 MB/s
(it seems good to me)

dd if=/dev/urandom of=/dd_test bs=1MB count=64 conv=fdatasync
64000000 bytes (64 MB, 61 MiB) copied, 0.681825 s, 93.9 MB/s

dd if=/dev/urandom of=/dd_test bs=1MB count=1024 conv=fdatasync
1024000000 bytes (1.0 GB, 977 MiB) copied, 8.17487 s, 125 MB/s
(It doesn’t seem bad to me)

can you help me?
if for you is slow disk , i know and i can not do anything about it . ok i accept my server limit

thank you in advance

2

Is it any quicker to backup to file locally then do the transfer and delete the local copy?
I have no idea if this is what actually happens using Virtualmin backup.
[my thoughts are the backup is depending on the partial write at the remote - 400G seems like a lot to do in one go]

3

ok, but on old server (another provider) i mount same remote sshfs and write directly without issue at 200mps.
and was ever 400gb to transfer…

in other words, if i check with iftop / vnstat during backup when i use
default gzip = about 50mbps
zip = 80/85 mbps
tar = 200 mbps
try more days same speed…

so i tend to exclude bandwith
cpu is not used at 100% during backup

so only thing i can suppose is speed of read/write of disk.
i know that new server is hosted on a proxmox cluster with ceph…
maybe ceph have some delay for backup?

but i hosted mail and works very quickly, also a VM with mysql have nice performance…
is only backup i can’t understand …

thank you again

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