Snapshot Speed Problem

informant

Renowned Member
Jan 31, 2012
762
10
83
Hi all,

if we make a snapshot ov a VM/CT we have very slow speed.
PHP:
 Total bytes written: 1770199040 (1.7GiB, 12MiB/s)
If we do start a hdd speedtest, we have over 500mb/s. We have test it on a modular server and on a hp blade server. We have test it with small vm´s/ct´s and with big vm´s/ct´s -> smae issue. Do you have a idea to fix it or what we can do to have a faster speed on backup vm´s/ct´s?

Very thanks.

regards
 
Hello Dietmar,

we use auto-backup LVM snapshot
PHP:
creating lvm snapshot of /dev/mapper/pve-data ('/dev/pve/vzsnap-phoenix-0')

I hope, this is the info, if you need.

regards
 
we use auto-backup LVM snapshot

LVM snapshots are known for bad write performance. Our new KVM backup system does not use LVM snapshots anymore (will be available with version 2.3). If you use containers, you can also try suspend mode instead.
 
Hi Dietmar,

very thanks for your information.
Suspend mode is only for containe. For VM we must use lvm - right?
Is the container offline in backup time, if we use suspend mode?

i have test in suspend mode with 16mb/s. is this the fastest?
PHP:
INFO: starting new backup job: vzdump 5530 --remove 0 --mode suspend --compress gzip --storage backups --node phoenix
INFO: Starting Backup of VM 5530 (openvz)
INFO: CTID 5530 exist mounted running
INFO: status = running
INFO: backup mode: suspend
INFO: ionice priority: 7
INFO: starting first sync /var/lib/vz/private/5530/ to /backups/dump/vzdump-openvz-5530-2013_02_02-16_01_23.tmp
INFO: Number of files: 32982
INFO: Number of files transferred: 26590
INFO: Total file size: 1787929671 bytes
INFO: Total transferred file size: 1787279164 bytes
INFO: Literal data: 1787279164 bytes
INFO: Matched data: 0 bytes
INFO: File list size: 778932
INFO: File list generation time: 0.001 seconds
INFO: File list transfer time: 0.000 seconds
INFO: Total bytes sent: 1789424028
INFO: Total bytes received: 527083
INFO: sent 1789424028 bytes  received 527083 bytes  13308186.70 bytes/sec
INFO: total size is 1787929671  speedup is 1.00
INFO: first sync finished (135 seconds)
INFO: suspend vm
INFO: Setting up checkpoint...
INFO:     suspend...
INFO:     get context...
INFO: Checkpointing completed successfully
INFO: starting final sync /var/lib/vz/private/5530/ to /backups/dump/vzdump-openvz-5530-2013_02_02-16_01_23.tmp
INFO: Number of files: 32985
INFO: Number of files transferred: 14
INFO: Total file size: 1787942801 bytes
INFO: Total transferred file size: 237785725 bytes
INFO: Literal data: 30245 bytes
INFO: Matched data: 237755480 bytes
INFO: File list size: 778974
INFO: File list generation time: 0.001 seconds
INFO: File list transfer time: 0.000 seconds
INFO: Total bytes sent: 920711
INFO: Total bytes received: 185922
INFO: sent 920711 bytes  received 185922 bytes  316180.86 bytes/sec
INFO: total size is 1787942801  speedup is 1615.66
INFO: final sync finished (3 seconds)
INFO: resume vm
INFO: Resuming...
INFO: vm is online again after 3 seconds
INFO: creating archive '/backups/dump/vzdump-openvz-5530-2013_02_02-16_01_23.tar.gz'
INFO: Total bytes written: 1811261440 (1.7GiB, 16MiB/s)
INFO: archive file size: 633MB
INFO: Finished Backup of VM 5530 (00:04:09)
INFO: Backup job finished successfully
TASK OK

regards
 
Last edited:
Suspend mode is only for container. For VM we must use lvm - right?

yes.

Is the container offline in backup time, if we use suspend mode?

For a short time (3 seconds on the example you posted). It uses a two-phase rsync algorithm to keep that time short.

i have test in suspend mode with 16mb/s. is this the fastest?

That depends on the speed of your storage, and if you have many small files inside the container.
 

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