uot;
À: "Alexandre DERUMIER"
Cc: "Dietmar Maurer" , qemu-devel@nongnu.org
Envoyé: Vendredi 23 Novembre 2012 15:58:09
Objet: Re: [Qemu-devel] qcow2: slow internal snapshot creation
Am 23.11.2012 15:17, schrieb Alexandre DERUMIER:
>>> Preallocation doesn't matter much
Am 23.11.2012 08:26, schrieb Dietmar Maurer:
> qcow2 snapshot on newly created files are fast:
>
> # qemu-img create -f qcow2 test.img 200G
> # time qemu-img snapshot -c snap1 test.img
> real 0m0.014s
>
> but if metadata is allocated it gets very slow:
>
> # qemu-img create -f qcow2 -o "p
Am 23.11.2012 15:17, schrieb Alexandre DERUMIER:
>>> Preallocation doesn't matter much these days.
>
> I have done benchmark through nfs on a netapp san, (with directio),
>
> I got 300 iops without preallocation, and 6000 iops with preallocation
This doesn't sound right, even for writethrou
t;
Cc: "Dietmar Maurer" , qemu-devel@nongnu.org
Envoyé: Vendredi 23 Novembre 2012 15:09:15
Objet: Re: [Qemu-devel] qcow2: slow internal snapshot creation
Am 23.11.2012 15:03, schrieb Alexandre DERUMIER:
> performance is also reduced when snapshot exist. (like if they are no
> preall
Am 23.11.2012 15:03, schrieb Alexandre DERUMIER:
> performance is also reduced when snapshot exist. (like if they are no
> preallocated metadatas)
Preallocation doesn't matter much these days.
> see initial git commit
>
> http://git.qemu.org/?p=qemu.git;a=commit;h=a35e1c177debb01240243bd656caca
g
Cc: "Kevin Wolf (kw...@redhat.com)"
Envoyé: Vendredi 23 Novembre 2012 08:26:13
Objet: [Qemu-devel] qcow2: slow internal snapshot creation
qcow2 snapshot on newly created files are fast:
# qemu-img create -f qcow2 test.img 200G
# time qemu-img snapshot -c snap1 test.img
real 0m0.014s
b
qcow2 snapshot on newly created files are fast:
# qemu-img create -f qcow2 test.img 200G
# time qemu-img snapshot -c snap1 test.img
real 0m0.014s
but if metadata is allocated it gets very slow:
# qemu-img create -f qcow2 -o "preallocation=metadata" test.img 200G
# time qemu-img snapshot -
