Cloning to nfs storage take long time


New Member
Aug 19, 2023
Hi, i have a local testvm with 14G, so i will clone them to a new one but with shared storage nfs.
The shared storage server is a truenas.
now i can see the networkbandwith is only 2Mib
but the net and the storage server has 1GiB net

on my old system it uses the same storage server i have a bandwith with +100MiB and more

why is this so slow,

create full clone of drive scsi0 (vmdata:vm-100-disk-0)
Formatting '/mnt/pve/nfs-pool2/images/101/vm-101-disk-0.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off preallocation=metadata compression_type=zlib size=15032385536 lazy_refcounts=off refcount_bits=16
transferred 0.0 B of 14.0 GiB (0.00%)
transferred 143.4 MiB of 14.0 GiB (1.00%)
transferred 288.2 MiB of 14.0 GiB (2.01%)
transferred 431.5 MiB of 14.0 GiB (3.01%)
transferred 576.3 MiB of 14.0 GiB (4.02%)
transferred 719.7 MiB of 14.0 GiB (5.02%)

is this the convertation from .img to .qcow2 what takes so long?

Bildschirmfoto 2023-08-19 um 19.52.00.png
Last edited:
is this the convertation from .img to .qcow2 what takes so long?
user iPerf to test your network between the hosts - can you achieve expected bandwidth when there is no disk or application involved?
use fio to test the disk access - are you seeing expected IOPS throughput when the sole purpose of application is to write to disk?

If the two above work as expected, then possibly the conversion (or rather slow CPU (due to contention?)) could play a role. May be its all 3. Or may be its jus a bad cable.
The only way to be sure is to reduce the number of problem participants to minimum and isolate various parts.

Good luck

Blockbridge : Ultra low latency all-NVME shared storage for Proxmox -
when i copy the image back from the nsf to local storage ist over 100MiB, there is no bad cable, the server is a smaal supermicro
i think its because the conversion and the cpu 4 x Intel(R) Atom(TM) CPU C2550, its only a test machine.

can i also use qcow2 for local storage? or is this only for sharad storage?
ok thanks for the answares, i am almost done with the testsetup :)
so the next step is backe a production setup.


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