From 51c95fc11727532e3b0d98c8470a6b60907a0680 Mon Sep 17 00:00:00 2001
From: Thomas Schwinge <tschwinge@gnu.org>
Date: Tue, 8 Jan 2013 21:31:31 +0100
Subject: IRC.

---
 hurd/running/qemu/writeback_caching.mdwn | 35 +++++++++++++++++++++++++++-----
 1 file changed, 30 insertions(+), 5 deletions(-)

(limited to 'hurd/running/qemu/writeback_caching.mdwn')

diff --git a/hurd/running/qemu/writeback_caching.mdwn b/hurd/running/qemu/writeback_caching.mdwn
index c9c53e3e..3b6c366b 100644
--- a/hurd/running/qemu/writeback_caching.mdwn
+++ b/hurd/running/qemu/writeback_caching.mdwn
@@ -1,5 +1,5 @@
-[[!meta copyright="Copyright © 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012
-Free Software Foundation, Inc."]]
+[[!meta copyright="Copyright © 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012,
+2013 Free Software Foundation, Inc."]]
 
 [[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
 id="license" text="Permission is granted to copy, distribute and/or modify this
@@ -13,7 +13,8 @@ License|/fdl]]."]]"""]]
 
 [[!tag open_issue_documentation]]
 
-IRC, freenode, #hurd, 2011-06-07
+
+# IRC, freenode, #hurd, 2011-06-07
 
     <braunr> hm, i guess i should have used cache=writeback with kvm before
       starting the debian installer :/
@@ -57,7 +58,8 @@ IRC, freenode, #hurd, 2011-06-07
     <braunr> well, if there is no I/O during downloading, downloading is faster
       :)
 
-IRC, freenode, #hurd, 2011-06-08
+
+# IRC, freenode, #hurd, 2011-06-08
 
     <braunr> youpi: does xen provide disk caching options ?
     <youpi> through a blktap, probably
@@ -70,7 +72,8 @@ IRC, freenode, #hurd, 2011-06-08
     <braunr> it really makes the hurd run a lot faster
     <braunr> as a workaround for emulators until I/O is reworked, ofc
 
-IRC, freenode, #hurd, 2011-06-09
+
+# IRC, freenode, #hurd, 2011-06-09
 
     <gnu_srs> braunr recommends to use writeback caching with kvm. Is this
       really recommended with the frequent crashes I experience?
@@ -88,3 +91,25 @@ IRC, freenode, #hurd, 2011-06-09
       as soon as the data is present in the host page cache.  This is safe as
       long as you trust your host.  If your host crashes or loses power, then
       the guest may experience data corruption." (from the qemu manpage)
+
+
+# IRC, freenode, #hurd, 2012-12-30
+
+    <gg0> http://bugs.debian.org/622319#51
+    <gg0> braunr: just pointing out writeback is default since qemu 1.3.0
+    <gg0> that makes hurd VMs faster by default :p
+    <braunr> ahh :)
+    <gg0> about data loss I had read (qemu man pages?) it may occur in case of
+      loss of power
+    <braunr> well yes
+    <gg0> probably on hurd may occur even with writethrough due to non
+      journaled ext2
+    <braunr> yes but the hurd flushes everything (and i mean everything) every
+      5 seconds
+    <gg0> http://lists.gnu.org/archive/html/qemu-devel/2012-02/msg02682.html
+    <braunr> so it's actually less likely to lose data because of the hurd than
+      because of power loss
+    <braunr> what i meant earlier is that we've never experienced unexpected
+      data loss because of qemu writeback policy
+    <braunr> if data is in the host cache and you lose power, qemu or not, you
+      lose data
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