Re: [ovirt-users] OVirt 4.1.2 - trim/discard on HDD/XFS/NFS contraproductive

> Von: Yaniv Kaul [yk...@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 > contraproductive On Sat, Jun 17, 2017 at 1:25 AM, Markus Stockhausen <st

Re: [ovirt-users] OVirt 4.1.2 - trim/discard on HDD/XFS/NFS contraproductive

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

Re: [ovirt-users] OVirt 4.1.2 - trim/discard on HDD/XFS/NFS contraproductive

4.1.2 - trim/discard on HDD/XFS/NFS contraproductive > Le 18 juin 2017 à 08:00, Idan Shaby <ish...@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 SCS

Re: [ovirt-users] OVirt 4.1.2 - trim/discard on HDD/XFS/NFS contraproductive

> Le 18 juin 2017 à 08:00, Idan Shaby 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. >

Re: [ovirt-users] OVirt 4.1.2 - trim/discard on HDD/XFS/NFS contraproductive

On Sat, Jun 17, 2017 at 1:25 AM, Markus Stockhausen 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

Re: [ovirt-users] OVirt 4.1.2 - trim/discard on HDD/XFS/NFS contraproductive

בתאריך יום א׳, 18 ביוני 2017, 9:01, מאת Idan Shaby ‏: > 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.

Re: [ovirt-users] OVirt 4.1.2 - trim/discard on HDD/XFS/NFS contraproductive

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.

[ovirt-users] OVirt 4.1.2 - trim/discard on HDD/XFS/NFS contraproductive

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