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<DIV><FONT size=2 face=Arial>Hi to all</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=2 face=Arial>Only as comment:<BR></FONT></DIV>
<DIV><FONT size=2 face=Arial>1) While that the VM have write cache configured as
none (that means write cache in VM guest), don't matter if the storage is DRBD,
local, CEPH or Gluster, always the VM will have the cache of write in RAM, and
obviously these data will not be in the disk or in the RAID controller of the
storage selected.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=2 face=Arial>2) The formula unique that i know for get that the
data always are in the RAID controller or in the dishes of disks is with the
combination of:<BR>- OS of the guest with write cache disabled or with
disk_barrires enabled.<BR>- QEMU configured for the VM with directsync or
writethrough.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=2 face=Arial>3) About of swap disk in Linux, i guess that with
directsync or writethrough will be sufficient, but i am not sure.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=2 face=Arial>@Dietmar:<BR>I believe that Mr. Stanislav say us
that as a cache of write is in the RAM, and these data don't go to the hard
disks or to the RAID controller, then these data aren't replicated with DRBD,
and as a negative effect, if the host crashes or breaks down, there will be an
irretrievable loss of data in the DRBD storage.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Best regards</FONT></DIV>
<DIV><FONT size=2 face=Arial>Cesar Peschiera</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT></DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=ginermail@gmail.com href="mailto:ginermail@gmail.com">Stanislav
German-Evtushenko</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=aderumier@odiso.com
href="mailto:aderumier@odiso.com">Alexandre DERUMIER</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Cc:</B> <A title=pve-devel@pve.proxmox.com
href="mailto:pve-devel@pve.proxmox.com">pve-devel@pve.proxmox.com</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Tuesday, November 18, 2014 2:25
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [pve-devel] Default cache
mode for VM hard drives</DIV>
<DIV><BR></DIV>
<DIV dir=ltr><BR>
<DIV class=gmail_extra>
<DIV class=gmail_quote>On Tue, Nov 18, 2014 at 8:17 PM, Alexandre DERUMIER
<SPAN dir=ltr><<A href="mailto:aderumier@odiso.com"
target=_blank>aderumier@odiso.com</A>></SPAN> wrote:<BR>
<BLOCKQUOTE
style="BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex"
class=gmail_quote><SPAN>>>What is your vm guest os ? kernel version
?<BR>>><BR>>>Guest OS can be Windows (any) and Linux (any
version).<BR><BR></SPAN>I ask the question because old windows virtio driver
don't send flush correctly,<BR><BR>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 ..)<BR><A
href="http://monolight.cc/2011/06/barriers-caches-filesystems/"
target=_blank>http://monolight.cc/2011/06/barriers-caches-filesystems/</A><BR><SPAN><BR>>>2.
It is often happen to Linux VM swap space.<BR></SPAN>mmm,good point, I don't
known how flush is working with swap </BLOCKQUOTE>
<DIV><BR></DIV>
<DIV>graylog2 was installed on Ubuntu 14.04 (virtio as I remember, not checked
with ide)<BR><BR></DIV>
<DIV>However:<BR></DIV>
<DIV>1) moving to IDE didn't help for Windows<BR></DIV>
<DIV>2) moving to IDE can't help for swap<BR></DIV>
<DIV>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)<BR><BR></DIV>
<DIV>Stanislav<BR></DIV></DIV></DIV></DIV>
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