12:57 p.m.
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Hi,
we have some really large snapshots left from a migration. Since our
store is almost full now we have to delete them now.
Some snapshots are around 1TB already.
The last time we tried to delete a ~500GB snapshot the delete task
blocked the whole diskstore's IO and the whole cluster and all hosts
became unavailable.
Is there a way to delete large snapshots in a "humane" way that will not
block everything?
Cheers,
Stefan
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1:08 p.m.
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Do you see swapping on the SPM? If yes a regular echo 3 > drop_caches could=
help.
Markus
Am 27.10.2014 10:57 schrieb Stefan Wendler <stefan.wendler(a)tngtech.com>:
Hi,
we have some really large snapshots left from a migration. Since our
store is almost full now we have to delete them now.
Some snapshots are around 1TB already.
The last time we tried to delete a ~500GB snapshot the delete task
blocked the whole diskstore's IO and the whole cluster and all hosts
became unavailable.
Is there a way to delete large snapshots in a "humane" way that will not
block everything?
Cheers,
Stefan
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<html <head <meta http-equiv=3D"Content-Type"
content=3D"text/html; charset=3Dus-ascii"=
<meta name=3D"Generator" content=3D"Microsoft
Exchange Server" <!-- converted from text
--><style><!-- .EmailQuote { margin-left: 1pt; pad=
ding-left: 4pt; border-left: #800000 2px solid; } --></style </head
<body <div <p
dir=3D"ltr">Do you see swapping on the SPM? If yes a regular echo 3
>=
drop_caches could help.</p <p
dir=3D"ltr">Markus</p <div
class=3D"x_quote">Am 27.10.2014 10:57 schrieb Stefan Wendler <stefa=
n.wendler@tngtech.com>:<br type=3D"attribution" </div
</div <font
size=3D"2"><span style=3D"font-size:10pt;" <div class=3D"PlainText">Hi,<br <br we have some really large snapshots
left from a migration. Since our<br store is
almost full now we have to delete them now.<br
<br Some snapshots are around 1TB
already.<br <br The last
time we tried to delete a ~500GB snapshot the delete task<br blocked the whole diskstore's IO and the whole cluster and
all hosts<br became unavailable.<br <br Is there a way to delete large
snapshots in a "humane" way that w=
ill not<br block everything?<br <br Cheers,<br Stefan<br
<br </div </span></font
</body </html
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Hi,
do you mean during snapshot deletion or in general?
In general we do not have any swap usage at all. On none of the 4 hosts.
We had some swap I/O on the host that is SPM most of the time. But not
during that period where we tried to delete the snapshot.
Cheers,
Stefan
On 10/27/14 11:08, Markus Stockhausen wrote:
Do you see swapping on the SPM? If yes a regular echo 3 >
drop_caches c=
ould help.
=20
Markus
=20
Am 27.10.2014 10:57 schrieb Stefan Wendler <stefan.wendler(a)tngtech.com>=
:
Hi,
=20
we have some really large snapshots left from a migration. Since our
store is almost full now we have to delete them now.
=20
Some snapshots are around 1TB already.
=20
The last time we tried to delete a ~500GB snapshot the delete task
blocked the whole diskstore's IO and the whole cluster and all hosts
became unavailable.
=20
Is there a way to delete large snapshots in a "humane" way that will no=
t
block everything?
=20
Cheers,
Stefan
=20
=20
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3:07 p.m.
This is a multi-part message in MIME format.
------=_NextPartTM-000-a0780f88-f591-414a-acb9-ba0b16afdc8d
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
Von: Stefan Wendler [stefan.wendler(a)tngtech.com]=0A=
Gesendet: Montag, 27. Oktober 2014 11:39=0A=
An: Markus Stockhausen=0A=
Cc: users(a)ovirt.org=0A=
Betreff: Re: [ovirt-users] Deleting large snapshots blocks the whole clus=
ter=0A=
=0A=
Hi,=0A=
=0A=
do you mean during snapshot deletion or in general?=0A=
=0A=
In general we do not have any swap usage at all. On none of the 4 hosts.=
=0A=
=0A=
We had some swap I/O on the host that is SPM most of the time. But not=0A=
during that period where we tried to delete the snapshot.=0A=
=0A=
=0A=
I thought of the bug described in RH bugzilla 1138690 "[SCALE] snapshot del=
etion -> =0A=
heavy swapping on SPM". In case you have no access to it (as it is RHEV tag=
ged): =0A=
=0A=
qemu-img reads through pagecache during snapshot deletion. A new flag has b=
een =0A=
intrduced in August this year that allows to avoid page cache. This flag mu=
st be=0A=
provided by OVirt/RHEV. Target release is 3.6. =0A=
=0A=
Until then the only bugfix is to drop pagecache manually on regular interva=
ls on the =0A=
hypversior and especially the SPM node.=0A=
=0A=
Markus=0A=
=0A=
=0A=
Cheers,=0A=
Stefan=0A=
=0A=
On 10/27/14 11:08, Markus Stockhausen wrote:=0A=
> Do you see swapping on the SPM? If yes a regular echo 3 > drop_caches c=
ould help.=0A=
>=0A=
> Markus=0A=
>=0A=
> Am 27.10.2014 10:57 schrieb Stefan Wendler <stefan.wendler(a)tngtech.com>=
:=0A=
> Hi,=0A=
>=0A=
> we have some really large snapshots left from a migration. Since our=0A=
> store is almost full now we have to delete them now.=0A=
>=0A=
> Some snapshots are around 1TB already.=0A=
>=0A=
> The last time we tried to delete a ~500GB snapshot the delete task=0A=
blocked the whole diskstore's IO and the whole cluster and all hosts=0A=
became unavailable.=0A=
=0A=
Is there a way to delete large snapshots in a "humane" way that will not=
=0A=
block everything?=0A=
=0A=
Cheers,=0A=
Stefan=0A=
=0A=
=0A=
=0A=
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manipuliert werden. Deshalb ist diese als E-Mail verschickte Nachricht keine
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Collogia
Unternehmensberatung AG
Ubierring 11
D-50678 Köln
Vorstand:
Kadir Akin
Dr. Michael Höhnerbach
Vorsitzender des Aufsichtsrates:
Hans Kristian Langva
Registergericht: Amtsgericht Köln
Registernummer: HRB 52 497
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e-mail is strictly forbidden.
e-mails sent over the internet may have been written under a wrong name or
been manipulated. That is why this message sent as an e-mail is not a
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Collogia
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I see. Then I will keep an eye on this tonight where we have a huge "all
ovirt downtime" just to delete those snapshots ^^
Thanks and Cheers,
Stefan
On 10/27/14 13:07, Markus Stockhausen wrote:
> Von: Stefan Wendler [stefan.wendler(a)tngtech.com]
> Gesendet: Montag, 27. Oktober 2014 11:39
> An: Markus Stockhausen
> Cc: users(a)ovirt.org
> Betreff: Re: [ovirt-users] Deleting large snapshots blocks the whole c=
luster
>
> Hi,
>
> do you mean during snapshot deletion or in general?
>
> In general we do not have any swap usage at all. On none of the 4 host=
s.
>
> We had some swap I/O on the host that is SPM most of the time. But not=
> during that period where we tried to delete the snapshot.
>
=20
I thought of the bug described in RH bugzilla 1138690 "[SCALE] snapshot=
deletion ->=20
heavy swapping on SPM". In case you have no access to it (as it
is RHEV=
tagged):=20
=20
qemu-img reads through pagecache during snapshot deletion. A new flag h=
as
been=20
intrduced in August this year that allows to avoid page cache. This
fla=
g must be
provided by OVirt/RHEV. Target release is 3.6.=20
=20
Until then the only bugfix is to drop pagecache manually on regular int=
ervals on
the=20
hypversior and especially the SPM node.
=20
Markus
=20
>
> Cheers,
> Stefan
>
> On 10/27/14 11:08, Markus Stockhausen wrote:
>> Do you see swapping on the SPM? If yes a regular echo 3 > drop_caches=
could help.
>>
>> Markus
>>
>> Am 27.10.2014 10:57 schrieb Stefan Wendler <stefan.wendler(a)tngtech.co=
m>:
>> Hi,
>>
>> we have some really large snapshots left from a migration. Since our
>> store is almost full now we have to delete them now.
>>
>> Some snapshots are around 1TB already.
>>
>> The last time we tried to delete a ~500GB snapshot the delete task
> blocked the whole diskstore's IO and the whole cluster and all hosts
> became unavailable.
>
> Is there a way to delete large snapshots in a "humane" way that will n=
ot
> block everything?
>
> Cheers,
> Stefan
>
>
=20
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3679
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3679
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4 comments
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Markus Stockhausen -
Stefan Wendler