5:25 p.m.
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Hi,
we just set up a new 4.1.2 OVirt cluster. It is a quite normal
HDD/XFS/NFS stack that worked quit well with 4.0 in the past.
Inside the VMs we use XFS too.
To our surprise we observe abysmal high IO during mkfs.xfs
and fstrim inside the VM. A simple example:
Step 1: Create 100G Thin disk
Result 1: Disk occupies ~10M on storage
Step 2: Format disk inside VM with mkfs.xfs
Result 2: Disk occupies 100G on storage
Changing the discard flag on the disk does not have any effect.
Am I missing something?
Best regards.
Markus
--_000_12EF8D94C6F8734FB2FF37B9FBEDD173010E01F673EXCHANGEcollo_
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Content-Transfer-Encoding: quoted-printable
<html dir=3D"ltr">
<head>
<meta http-equiv=3D"Content-Type" content=3D"text/html;
charset=3Diso-8859-=
1">
<style type=3D"text/css" id=3D"owaParaStyle"></style>
</head>
<body fpstyle=3D"1" ocsi=3D"0">
<div style=3D"direction: ltr;font-family: Arial;color: #000000;font-size: 1=
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<div style=3D"font-family:Tahoma; font-size:13px">
<div style=3D"font-family:Tahoma; font-size:13px">
<div style=3D"font-family:Tahoma; font-size:13px">
<div>
<div>Hi, </div>
<div><br>
</div>
<div>we just set up a new 4.1.2 OVirt cluster. It is a quite normal</div>
<div>HDD/XFS/NFS stack that worked quit well with 4.0 in the past. </d=
iv>
<div>Inside the VMs we use XFS too.</div>
<div><br>
</div>
<div>To our surprise we observe abysmal high IO during
mkfs.xfs </div>
<div>and fstrim inside the VM. A simple example:</div>
<div><br>
</div>
<div>Step 1: Create 100G Thin disk</div>
<div>Result 1: Disk occupies ~10M on storage</div>
<div><br>
</div>
<div>Step 2: Format disk inside VM with mkfs.xfs</div>
<div>Result 2: Disk occupies 100G on storage</div>
<div><br>
</div>
<div>Changing the discard flag on the disk does not have any effect.</div>
<div><br>
</div>
<div>Am I missing something?</div>
<div><br>
</div>
<div>Best regards.</div>
<div><br>
</div>
<div>Markus</div>
</div>
</div>
</div>
</div>
</div>
<div id=3D"ofmeet-extension-installed"
style=3D"display:none"></div>
</div>
</div>
</body>
</html>
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1 a.m.
Hi Markus,
AFAIK, mkfs.xfs tries to discard all the blocks before formatting the
device.
If you don't want it to do that, you can use the "-K Do not attempt to
discard blocks at mkfs time" option of mkfs.xfs.
In oVirt 4.1 we introduced the "Enable Discard" flag for a virtual
machine's disk.
When enabled, qemu is configured to pass on live UNMAP SCSI commands from
the guest to the underlying storage.
If you don't need live discarding, shutdown the VM and disable the "Enable
Discard" option. That will cause qemu to ignore the live UNMAP SCSI
commands coming from the guest and not pass it on to the underlying storage.
Note that this makes fstrim completely redundant, as the purpose of the
command is to discard unused blocks under the given path.
Regards,
Idan
On Sat, Jun 17, 2017 at 1:25 AM, Markus Stockhausen <stockhausen(a)collogia.de
wrote:
Hi,
we just set up a new 4.1.2 OVirt cluster. It is a quite normal
HDD/XFS/NFS stack that worked quit well with 4.0 in the past.
Inside the VMs we use XFS too.
To our surprise we observe abysmal high IO during mkfs.xfs
and fstrim inside the VM. A simple example:
Step 1: Create 100G Thin disk
Result 1: Disk occupies ~10M on storage
Step 2: Format disk inside VM with mkfs.xfs
Result 2: Disk occupies 100G on storage
Changing the discard flag on the disk does not have any effect.
Am I missing something?
Best regards.
Markus
_______________________________________________
Users mailing list
Users(a)ovirt.org
http://lists.ovirt.org/mailman/listinfo/users
1:29 a.m.
בתאריך יום א׳, 18 ביוני 2017, 9:01, מאת Idan Shaby <ishaby(a)redhat.com>:
Hi Markus,
AFAIK, mkfs.xfs tries to discard all the blocks before formatting the
device.
If you don't want it to do that, you can use the "-K Do not attempt to
discard blocks at mkfs time" option of mkfs.xfs.
In oVirt 4.1 we introduced the "Enable Discard" flag for a virtual
machine's disk.
When enabled, qemu is configured to pass on live UNMAP SCSI commands from
the guest to the underlying storage.
If you don't need live discarding, shutdown the VM and disable the "Enable
Discard" option. That will cause qemu to ignore the live UNMAP SCSI
commands coming from the guest and not pass it on to the underlying storage.
Note that this makes fstrim completely redundant, as the purpose of the
command is to discard unused blocks under the given path.
I think we need a bug for this, both fo documrnting this issue, and to
investigate why discarding unused blocks allocate and zero all blocks. This
behaviour is unhelpful.
Markus, can you check if performing the same discard from the host leads to
same result?
Regards,
Idan
On Sat, Jun 17, 2017 at 1:25 AM, Markus Stockhausen <
stockhausen(a)collogia.de> wrote:
> Hi,
>
> we just set up a new 4.1.2 OVirt cluster. It is a quite normal
> HDD/XFS/NFS stack that worked quit well with 4.0 in the past.
> Inside the VMs we use XFS too.
>
> To our surprise we observe abysmal high IO during mkfs.xfs
> and fstrim inside the VM. A simple example:
>
> Step 1: Create 100G Thin disk
> Result 1: Disk occupies ~10M on storage
>
> Step 2: Format disk inside VM with mkfs.xfs
> Result 2: Disk occupies 100G on storage
>
> Changing the discard flag on the disk does not have any effect.
>
> Am I missing something?
>
> Best regards.
>
> Markus
>
> _______________________________________________
> Users mailing list
> Users(a)ovirt.org
> http://lists.ovirt.org/mailman/listinfo/users
>
>
_______________________________________________
Users mailing list
Users(a)ovirt.org
http://lists.ovirt.org/mailman/listinfo/users
3:13 a.m.
Le 18 juin 2017 à 08:00, Idan Shaby <ishaby(a)redhat.com> a écrit
:
If you don't need live discarding, shutdown the VM and disable the "Enable
Discard" option. That will cause qemu to ignore the live UNMAP SCSI commands coming
from the guest and not pass it on to the underlying storage.
Note that this makes fstrim completely redundant, as the purpose of the command is to
discard unused blocks under the given path.
Redundant ? Useless you mean ? From my comprehension, the purpose to fstrim is to send
UNMAP SCSI on batch instead of mount -o discard that send them synchronously.
3:16 a.m.
This is a multi-part message in MIME format.
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Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
Thanks for all your feedback.=0A=
=0A=
Im trying to collect all the infos in BZ1462504.=0A=
=0A=
________________________________________=0A=
Von: Fabrice Bacchella [fabrice.bacchella(a)orange.fr]=0A=
Gesendet: Sonntag, 18. Juni 2017 10:13=0A=
An: Idan Shaby=0A=
Cc: Markus Stockhausen; Ovirt Users=0A=
Betreff: Re: [ovirt-users] OVirt 4.1.2 - trim/discard on HDD/XFS/NFS contra=
productive=0A=
=0A=
Le 18 juin 2017 =E0 08:00, Idan Shaby <ishaby(a)redhat.com> a
=E9crit :=0A=
If you don't need live discarding, shutdown the VM and disable the "Enabl=
e Discard" option. That will cause qemu to ignore the live UNMAP SCSI comma=
nds coming from the guest and not pass it on to the underlying storage.=0A=
Note that this makes fstrim completely redundant, as the purpose of
the c=
ommand is to discard unused blocks under the given path.=0A=
=0A=
Redundant ? Useless you mean ? From my comprehension, the purpose to fstrim=
is to send UNMAP SCSI on batch instead of mount -o discard that send them =
synchronously.=0A=
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Unternehmensberatung AG
Ubierring 11
D-50678 Köln
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Dr. Michael Höhnerbach
Vorsitzender des Aufsichtsrates:
Hans Kristian Langva
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3:18 a.m.
Right, but I just wanted to emphasize that disabling "Enable Discard" for
that disk will cause qemu to ignore these UNMAP commands and not pass it on
to the underlying storage.
So if you've got this flag disabled, there's no reason to use fstrim. It
makes sense to use it only when enabling "Discard enabled".
Regards,
Idan
On Sun, Jun 18, 2017 at 11:13 AM, Fabrice Bacchella <
fabrice.bacchella(a)orange.fr> wrote:
> Le 18 juin 2017 à 08:00, Idan Shaby <ishaby(a)redhat.com> a écrit :
> If you don't need live discarding, shutdown the VM and disable the
"Enable Discard" option. That will cause qemu to ignore the live UNMAP SCSI
commands coming from the guest and not pass it on to the underlying storage.
> Note that this makes fstrim completely redundant, as the purpose of the
command is to discard unused blocks under the given path.
Redundant ? Useless you mean ? From my comprehension, the purpose to
fstrim is to send UNMAP SCSI on batch instead of mount -o discard that send
them synchronously.
2:58 a.m.
On Sat, Jun 17, 2017 at 1:25 AM, Markus Stockhausen <stockhausen(a)collogia.de
wrote:
Hi,
we just set up a new 4.1.2 OVirt cluster. It is a quite normal
HDD/XFS/NFS stack that worked quit well with 4.0 in the past.
Inside the VMs we use XFS too.
To our surprise we observe abysmal high IO during mkfs.xfs
and fstrim inside the VM. A simple example:
Step 1: Create 100G Thin disk
Result 1: Disk occupies ~10M on storage
Step 2: Format disk inside VM with mkfs.xfs
Result 2: Disk occupies 100G on storage
Changing the discard flag on the disk does not have any effect.
Are you sure it's discarding, at all?
1. NFS: only NFSv4.2 supports discard. Is that the case in your setup?
2. What's the value of /sys/block/<disk>/queue/discard_granularity ?
3. Can you share the mkfs.xfs command line?
4. Are you sure it's not a raw-sparse image?
Y.
Am I missing something?
Best regards.
Markus
_______________________________________________
Users mailing list
Users(a)ovirt.org
http://lists.ovirt.org/mailman/listinfo/users
3:31 a.m.
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boundary="_000_12EF8D94C6F8734FB2FF37B9FBEDD173010E01F85CEXCHANGEcollo_"
--_000_12EF8D94C6F8734FB2FF37B9FBEDD173010E01F85CEXCHANGEcollo_
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
<head <meta http-equiv=3D"Content-Type"
content=3D"text/html; charset=3Diso-8859-=
1" <style type=3D"text/css"
id=3D"owaParaStyle"></style
</head <body fpstyle=3D"1"
ocsi=3D"0" <div style=3D"direction:
ltr;font-family: Arial;color: #000000;font-size: 1=
0pt;" <div style=3D"font-family:
Times New Roman; color: #000000; font-size: 16px=
" <div id=3D"divRpF331137" style=3D"direction:
ltr;"><font face=3D"Tahoma" si=
ze=3D"2" color=3D"#000000"><b>> Von:</b> Yaniv
Kaul [ykaul(a)redhat.com]<b=
r <b>> Gesendet:</b> Sonntag, 18. Juni 2017
09:58<br <b>> An:</b>
Markus Stockhausen<br <b>> Cc:</b>
Ovirt Users<br <b>> Betreff:</b>
Re: [ovirt-users] OVirt 4.1.2 - trim/discard on HDD/XF=
S/NFS contraproductive<br </font></div <div id=3D"divRpF331137" style=3D"direction:
ltr;"><font face=3D"Tahoma" si=
ze=3D"2" color=3D"#000000"><br
</font></div <div <div
dir=3D"ltr" <div
class=3D"gmail_extra" <div
class=3D"gmail_quote">On Sat, Jun 17, 2017 at 1:25 AM, Markus Stockhau=
sen <span dir=3D"ltr" <<a
href=3D"mailto:stockhausen@collogia.de"
target=3D"_blank">stockhause=
n(a)collogia.de</a>&gt;</span> wrote:<br
<blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px
0.8ex; border=
-left:1px solid rgb(204,204,204); padding-left:1ex"
<div <div style=3D"direction:ltr;
font-family:Arial; color:rgb(0,0,0); font-size=
:10pt" <div
style=3D"font-family:Tahoma; font-size:13px" <div
style=3D"font-family:Tahoma; font-size:13px" <div
style=3D"font-family:Tahoma; font-size:13px" <div
style=3D"font-family:Tahoma; font-size:13px" <div
style=3D"font-family:Tahoma; font-size:13px"
<div <div>Hi, </div <div><br
</div <div>we just set up a new
4.1.2 OVirt cluster. It is a quite normal</div
<div>HDD/XFS/NFS stack that worked quit well with 4.0 in the
past. </d=
iv <div>Inside the VMs we use XFS too.</div <div><br
</div <div>To our surprise we
observe abysmal high IO during mkfs.xfs </div
<div>and fstrim inside the VM. A simple example:</div <div><br
</div <div>Step 1: Create 100G Thin
disk</div <div>Result 1: Disk occupies
~10M on storage</div <div><br </div
<div>Step 2: Format disk inside VM with mkfs.xfs</div <div>Result 2: Disk occupies 100G on storage</div <div><br
</div <div>Changing the discard flag
on the disk does not have any effect.</div
</div </div </div
</div </div </div
</div </div </blockquote
<div><br </div <div>> Are you sure it's discarding, at
all?</div <div>> 1. NFS: only
NFSv4.2 supports discard. Is that the case in your s=
etup?</div <div>> 2. What's
the value of /sys/block/<disk>/queue/discard=
_granularity ?</div <div>> 3. Can you share
the mkfs.xfs command line?</div <div>> 4. Are you sure
it's not a raw-sparse image?</div
<div><br </div <div>Questions should answered in BZ1462504. When talking
about thin</div <div>provisioned disks I'm
only referring to the OVirt disk-option. So I</d=
iv <div>might mix up something here. Nevertheless the
following is more than</=
div <div>strange for me:</div
<div><br </div <div>- Create disk image: File on storage is
small</div <div>- Format inside VM: File
on storage is fully allocated </div
<div>- Move around in Ovirt to another NFS storage: File is small again.
</=
div <div><br
</div <div>That means:</div <div>- mkfs.xfs inside VM and so qemu is hammering
(empty) data into all bl=
ocks</div <div>- But this data must be
zeros as they can be compated afterwards.</div=
<div><br
</div <div>Best regards.</div <div><br
</div <div>Markus</div <div><br
</div </div </div
</div </div </div
</div </body </html
--_000_12EF8D94C6F8734FB2FF37B9FBEDD173010E01F85CEXCHANGEcollo_--
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irrtümlich erhalten haben, informieren Sie bitte sofort den Absender und
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Weitergabe dieser Mail ist nicht gestattet.
Über das Internet versandte E-Mails können unter fremden Namen erstellt oder
manipuliert werden. Deshalb ist diese als E-Mail verschickte Nachricht keine
rechtsverbindliche Willenserklärung.
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
This e-mail may contain confidential and/or privileged information. If you
are not the intended recipient (or have received this e-mail in error)
please notify the sender immediately and destroy this e-mail. Any
unauthorized copying, disclosure or distribution of the material in this
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
legally binding declaration of intention.
Collogia
Unternehmensberatung AG
Ubierring 11
D-50678 Köln
executive board:
Kadir Akin
Dr. Michael Höhnerbach
President of the supervisory board:
Hans Kristian Langva
Registry office: district court Cologne
Register number: HRB 52 497
****************************************************************************
------=_NextPartTM-000-9c273f1c-a2dd-4aba-ab90-4aa24b5ef225--
Von: Yaniv Kaul [ykaul(a)redhat.com]
Gesendet: Sonntag, 18. Juni 2017 09:58
An: Markus Stockhausen
Cc: Ovirt Users
Betreff: Re: [ovirt-users] OVirt 4.1.2 - trim/discard on HDD/XFS/NFS cont=
raproductive
On Sat, Jun 17, 2017 at 1:25 AM, Markus Stockhausen <stockhausen(a)collogia.d=
e<mailto:stockhausen@collogia.de>> wrote:
Hi,
we just set up a new 4.1.2 OVirt cluster. It is a quite normal
HDD/XFS/NFS stack that worked quit well with 4.0 in the past.
Inside the VMs we use XFS too.
To our surprise we observe abysmal high IO during mkfs.xfs
and fstrim inside the VM. A simple example:
Step 1: Create 100G Thin disk
Result 1: Disk occupies ~10M on storage
Step 2: Format disk inside VM with mkfs.xfs
Result 2: Disk occupies 100G on storage
Changing the discard flag on the disk does not have any effect.
Are you sure it's discarding, at all?
1. NFS: only NFSv4.2 supports discard. Is that the case in your setup?
2. What's the value of /sys/block/<disk>/queue/discard_granularity ?
3. Can you share the mkfs.xfs command line?
4. Are you sure it's not a raw-sparse image?
Questions should answered in BZ1462504. When talking about thin
provisioned disks I'm only referring to the OVirt disk-option. So I
might mix up something here. Nevertheless the following is more than
strange for me:
- Create disk image: File on storage is small
- Format inside VM: File on storage is fully allocated
- Move around in Ovirt to another NFS storage: File is small again.
That means:
- mkfs.xfs inside VM and so qemu is hammering (empty) data into all blocks
- But this data must be zeros as they can be compated afterwards.
Best regards.
Markus
--_000_12EF8D94C6F8734FB2FF37B9FBEDD173010E01F85CEXCHANGEcollo_
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2744
days inactive
2746
days old
7 comments
5 participants
participants (5)
-
Fabrice Bacchella -
Idan Shaby -
Markus Stockhausen -
Nir Soffer -
Yaniv Kaul