<html dir="ltr">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<style type="text/css" id="owaParaStyle"></style>
</head>
<body fpstyle="1" ocsi="0">
<div style="direction: ltr;font-family: Arial;color: #000000;font-size: 10pt;">
<div style="font-family: Times New Roman; color: #000000; font-size: 16px">
<div id="divRpF331137" style="direction: ltr;"><font face="Tahoma" size="2" color="#000000"><b>> Von:</b> Yaniv Kaul [ykaul@redhat.com]<br>
<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/XFS/NFS contraproductive<br>
</font></div>
<div id="divRpF331137" style="direction: ltr;"><font face="Tahoma" size="2" color="#000000"><br>
</font></div>
<div>
<div dir="ltr">
<div class="gmail_extra">
<div class="gmail_quote">On Sat, Jun 17, 2017 at 1:25 AM, Markus Stockhausen <span dir="ltr">
<<a href="mailto:stockhausen@collogia.de" target="_blank">stockhausen@collogia.de</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex; border-left:1px solid rgb(204,204,204); padding-left:1ex">
<div>
<div style="direction:ltr; font-family:Arial; color:rgb(0,0,0); font-size:10pt">
<div style="font-family:Tahoma; font-size:13px">
<div style="font-family:Tahoma; font-size:13px">
<div style="font-family:Tahoma; font-size:13px">
<div style="font-family:Tahoma; font-size:13px">
<div style="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. </div>
<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 setup?</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</div>
<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 blocks</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>