Dne 15.7.2016 v 14:40 Navin P.S napsal(a):
On Fri, Jul 15, 2016 at 6:05 PM, Zdenek Kabelac <zkabelac@xxxxxxxxxx> wrote:
Dne 15.7.2016 v 14:15 Navin P.S napsal(a):
On Fri, Jul 15, 2016 at 5:21 PM, Mikulas Patocka <mpatocka@xxxxxxxxxx>
wrote:
On Fri, 15 Jul 2016, Navin P.S wrote:
Resend ..
On Thu, Jul 14, 2016 at 7:55 PM, Navin P.S <navinp1912@xxxxxxxxx> wrote:
Hi,
Can i do dd if=/dev/zero of=/dev/mapper/dmo count=20 ? where dmo is
a dm snapshot origin created through dmsetup command. Instead of
/dev/zero i can write valid devices.
I could create the dmo through some lvm2 commands.
lvcreate -s
Is direct write
with 4k (page size values ) allowed when it is mapped to 2 block
devices in linear mode ?
Regards,
-- Navin
I'm seeing OOM followed by reboot of host machine.
Does this mean this device cannot to exported to containers for writing
?
The snapshot driver requires 32 bytes of memory for one chunk (the chunk
size is selected with the "-c" switch to lvcreate). You should set system
memory according to that.
Mikulas
-- Navin
Are origin devices readonly ?
When i do dd if=/dev/zero of=/dev/mapper/ff count=10, it kills all the
process says OOM.
How do you go about debugging this ? I'm running 4.7.0-rc7+ .
root@vm-xenial-foo:~# dmsetup info
Name: cryptie4-ff
State: ACTIVE
Read Ahead: 256
Tables present: LIVE
Open count: 0
Event number: 0
Major, minor: 251, 0
Number of targets: 2
Name: ff
State: ACTIVE
Read Ahead: 256
Tables present: LIVE
Open count: 0
Event number: 0
Major, minor: 251, 1
Number of targets: 1
root@vm-xenial-foo:~# dmsetup status
cryptie4-ff: 0 102400 linear
cryptie4-ff: 102400 122880 linear
ff: 0 102400 snapshot-origin
root@vm-xenial-foo:~#
Hi
Maybe you should have started with reading documenation for snapshot target
?
linux/Documentation/device-mapper/snapshot.txt
It nowhere mentions that origin device is readonly. It says writes go
to COW device
and then you can merge it back.
Can you please paste the snippet ?
1) a device containing the original mapping table of the source volume;
2) a device used as the <COW device>;
3) a "snapshot" device, combining #1 and #2, which is the visible snapshot
volume;
4) the "original" volume (which uses the device number used by the original
source volume), whose table is replaced by a "snapshot-origin" mapping
from device #1.
Regards
Zdenek
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