I install new VM KVM Debian 6. Installation without a graphic environment. Made the schedule for backup. After backup the size of the file of a backup copy makes 20Gb!!! Why so? There is a similar empty VM with Centos 6.2 and there the backup copy occupies 3Gb.
Too large size of a backup copy. Why?
- Thread starter Static
- Start date
Yes!
System:
# uname -a
Linux ais-mfc 2.6.32-5-amd64 #1 SMP Thu Mar 22 17:26:33 UTC 2012 x86_64 GNU/Linux
# df -h
/dev/mapper/ais--mfc-root
66G 763M 62G 2% /
tmpfs 4,0G 0 4,0G 0% /lib/init/rw
udev 4,0G 120K 4,0G 1% /dev
tmpfs 4,0G 0 4,0G 0% /dev/shm
/dev/vda1 228M 16M 201M 8% /boot
After backup VM size = 20,3Gb, file format = tar.lzo
The first time such I see
System:
# uname -a
Linux ais-mfc 2.6.32-5-amd64 #1 SMP Thu Mar 22 17:26:33 UTC 2012 x86_64 GNU/Linux
# df -h
/dev/mapper/ais--mfc-root
66G 763M 62G 2% /
tmpfs 4,0G 0 4,0G 0% /lib/init/rw
udev 4,0G 120K 4,0G 1% /dev
tmpfs 4,0G 0 4,0G 0% /dev/shm
/dev/vda1 228M 16M 201M 8% /boot
After backup VM size = 20,3Gb, file format = tar.lzo
The first time such I see
try to zero out the free space inside the vm and you'll get very small backup archive:
dd if=/dev/zero of=zero.small.file bs=1024 count=102400
dd if=/dev/zero of=zero.file bs=1024
rm zero.small.file
sync ; sleep 60 ; sync
rm zero.file
in a windows vm you can use sdelete:
sdelete.exe -z c::
dd if=/dev/zero of=zero.small.file bs=1024 count=102400
dd if=/dev/zero of=zero.file bs=1024
rm zero.small.file
sync ; sleep 60 ; sync
rm zero.file
in a windows vm you can use sdelete:
sdelete.exe -z c::
[root@antispam ~]# dd if=/dev/zero of=zero.small.file bs=1024 count=102400
102400+0 records in
102400+0 records out
104857600 bytes (105 MB) copied, 6.50482 seconds, 16.1 MB/s
[root@antispam ~]# dd if=/dev/zero of=zero.file bs=1024
dd: writing `zero.file': No space left on device
28806481+0 records in
28806480+0 records out
29497835520 bytes (29 GB) copied, 1268.94 seconds, 23.2 MB/s
[root@antispam ~]# rm zero.small.file
rm: remove regular file `zero.small.file'? yes
Total size is 32 GB and about %80 of it was emtpy. I will need to run it on some other linux machine which has only %30 of total disk size empty. I will probably have no space left on device. Why is that ? Sorry I am not a linux expert.
102400+0 records in
102400+0 records out
104857600 bytes (105 MB) copied, 6.50482 seconds, 16.1 MB/s
[root@antispam ~]# dd if=/dev/zero of=zero.file bs=1024
dd: writing `zero.file': No space left on device
28806481+0 records in
28806480+0 records out
29497835520 bytes (29 GB) copied, 1268.94 seconds, 23.2 MB/s
[root@antispam ~]# rm zero.small.file
rm: remove regular file `zero.small.file'? yes
Total size is 32 GB and about %80 of it was emtpy. I will need to run it on some other linux machine which has only %30 of total disk size empty. I will probably have no space left on device. Why is that ? Sorry I am not a linux expert.
Zeroing out is ok maybe for a one-time. But in general, you should be using VirtIO-SCSI with "discard" enabled and run a periodic fstrim inside the guest. That will mark unused blocks and is much faster. With the dd method, those zeroes are actually written out to disk.
The fstrim we run daily is:
The fstrim we run daily is:
Code:
/sbin/fstrim -a -v -m 16m