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

[Alexandre DERUMIER]

>> However there were many issues with ext3 (no barriers by default) 
yes, I think that ext3 barrier are off by default until kernel 3.1

barrier should never disabled with cache=none or cache=writeback


About windows, which windows version ?  last virtio drivers ?


----- Mail original ----- 

De: "Stanislav German-Evtushenko" <ginermail at gmail.com> 
À: "Alexandre DERUMIER" <aderumier at odiso.com> 
Cc: pve-devel at pve.proxmox.com, "Dietmar Maurer" <dietmar at proxmox.com> 
Envoyé: Mardi 18 Novembre 2014 18:25:32 
Objet: Re: [pve-devel] Default cache mode for VM hard drives 





On Tue, Nov 18, 2014 at 8:17 PM, Alexandre DERUMIER < aderumier at odiso.com > wrote: 


>>What is your vm guest os ? kernel version ? 
>> 
>>Guest OS can be Windows (any) and Linux (any version). 

I ask the question because old windows virtio driver don't send flush correctly, 

and some linux kernel too (it's really safe since 2.6.32 - 2.6.33 if I remember, depend of filesystem, virtio driver -lvm-mdadm-dm version ..) 
http://monolight.cc/2011/06/barriers-caches-filesystems/ 

>>2. It is often happen to Linux VM swap space. 
mmm,good point, I don't known how flush is working with swap 




graylog2 was installed on Ubuntu 14.04 (virtio as I remember, not checked with ide) 


However: 

1) moving to IDE didn't help for Windows 

2) moving to IDE can't help for swap 

3) I don't remember if I tried ext4 in combination with ide because ext4 didn't produce any issues before I installed graylog2 recently. However there were many issues with ext3 (no barriers by default) 


Stanislav