[pve-devel] Default cache mode for VM hard drives

[Cesar Peschiera]

Hi to all

I use directsync in my VMs with DRBD 8.4.5 in four nodes (LVM on top of 
DRBD), since some months ago, never did have problems (all sunday days, a 
automated system verify all storages DRBD),

These are the version of packages of my PVE nodes:

In a pair of nodes:
Shell# pveversion -v
proxmox-ve-2.6.32: 3.3-139 (running kernel: 3.10.0-5-pve)
pve-manager: 3.3-5 (running version: 3.3-5/bfebec03)
pve-kernel-2.6.32-27-pve: 2.6.32-121
pve-kernel-3.10.0-5-pve: 3.10.0-19
pve-kernel-2.6.32-28-pve: 2.6.32-124
pve-kernel-2.6.32-29-pve: 2.6.32-126
pve-kernel-2.6.32-34-pve: 2.6.32-139
lvm2: 2.02.98-pve4
clvm: 2.02.98-pve4
corosync-pve: 1.4.7-1
openais-pve: 1.1.4-3
libqb0: 0.11.1-2
redhat-cluster-pve: 3.2.0-2
resource-agents-pve: 3.9.2-4
fence-agents-pve: 4.0.10-1
pve-cluster: 3.0-15
qemu-server: 3.3-3
pve-firmware: 1.1-3
libpve-common-perl: 3.0-19
libpve-access-control: 3.0-15
libpve-storage-perl: 3.0-25
pve-libspice-server1: 0.12.4-3
vncterm: 1.1-8
vzctl: 4.0-1pve6
vzprocps: 2.0.11-2
vzquota: 3.1-2
pve-qemu-kvm: 2.1-10
ksm-control-daemon: 1.1-1
glusterfs-client: 3.5.2-1

In other pair of nodes:
Shell# pveversion -v
proxmox-ve-2.6.32: 3.3-139 (running kernel: 3.10.0-5-pve)
pve-manager: 3.3-5 (running version: 3.3-5/bfebec03)
pve-kernel-3.10.0-5-pve: 3.10.0-19
pve-kernel-2.6.32-34-pve: 2.6.32-139
lvm2: 2.02.98-pve4
clvm: 2.02.98-pve4
corosync-pve: 1.4.7-1
openais-pve: 1.1.4-3
libqb0: 0.11.1-2
redhat-cluster-pve: 3.2.0-2
resource-agents-pve: 3.9.2-4
fence-agents-pve: 4.0.10-1
pve-cluster: 3.0-15
qemu-server: 3.3-5 <-particularly made by Alexandre
pve-firmware: 1.1-3
libpve-common-perl: 3.0-19
libpve-access-control: 3.0-15
libpve-storage-perl: 3.0-25
pve-libspice-server1: 0.12.4-3
vncterm: 1.1-8
vzctl: 4.0-1pve6
vzprocps: 2.0.11-2
vzquota: 3.1-2
pve-qemu-kvm: 2.2-2 <-particularly made by Alexandre
ksm-control-daemon: 1.1-1
glusterfs-client: 3.5.2-1




----- Original Message ----- 
From: "Alexandre DERUMIER" <aderumier at odiso.com>
To: "Stanislav German-Evtushenko" <ginermail at gmail.com>
Cc: "pve-devel" <pve-devel at pve.proxmox.com>
Sent: Monday, April 13, 2015 5:16 AM
Subject: Re: [pve-devel] Default cache mode for VM hard drives


> Hi,
>
> Another difference is that cache=none|directsync is that vm use aio=native 
> instead aio=threads.
>
>
> (you can try cache=none,aio=threads in you disk config to change the 
> behaviour).
>
> Maybe it doesn't work well with drbd.
>
>
> ----- Mail original -----
> De: "Stanislav German-Evtushenko" <ginermail at gmail.com>
> À: "dietmar" <dietmar at proxmox.com>
> Cc: "pve-devel" <pve-devel at pve.proxmox.com>, "aderumier" 
> <aderumier at odiso.com>
> Envoyé: Lundi 13 Avril 2015 10:23:19
> Objet: Re: [pve-devel] Default cache mode for VM hard drives
>
> Hello,
>
> I have an update on this issue.
>
> I have found circumstances when we get out of sync with directsync mode 
> and made more test. What I found out so far was that out of sync only 
> appear for cache modes with O_DIRECT, i.e. for those cache modes when host 
> cache is bypassed. Write-back and write-through modes do not produce out 
> of sync blocks with DRBD while "none" and "directsync" do.
>
> Best regards,
> Stanislav
>
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