Hello, I was wondering about sar under xen: is it more logical to install it on dom0 or in each domU? about disk i/o it should be able to give disk throughputs even in a dom0, and maybe, also about cpu usage, memory, etc. certanly installing sar in a domU will give those values, but will this be reliable? what''s your opinion about this? -- Edoardo _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
It depends on what information you are trying to obtain. If you want information about real hardware (cpu usage, nic''s in dom0 etc) installing in dom0 would be the best case. Installing in domU can give you good info about individual domain specific memory, network, tty usage etc, but cpu percentages may be quite artificial, and you wouldn''t be able to see real hardware bottlenecks without examining the other domains. _____ From: xen-users-bounces@lists.xensource.com [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of Edoardo Ceccarelli Sent: April 11, 2008 8:39 PM To: xen-users@lists.xensource.com Subject: [Xen-users] SAR in dom0 or domU Hello, I was wondering about sar under xen: is it more logical to install it on dom0 or in each domU? about disk i/o it should be able to give disk throughputs even in a dom0, and maybe, also about cpu usage, memory, etc. certanly installing sar in a domU will give those values, but will this be reliable? what''s your opinion about this? -- Edoardo _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
The abstraction that Xen gives should be enough to give reliable values in certain conditions, I was wondering about disk troughput for example: using LVM the dom0 sar shouldn''t even be able to produce values cause it cannot mount the partition on the other hand the xenU domain should give pretty reliable values... has anybody tried to compare sar results on xen? ...about cpu''s, I completely agree with you On Sun, Apr 13, 2008 at 5:38 PM, [STD]Ein <ein@anti-logic.com> wrote:> It depends on what information you are trying to obtain. > > > > If you want information about real hardware (cpu usage, nic''s in dom0 etc) > installing in dom0 would be the best case. Installing in domU can give > you good info about individual domain specific memory, network, tty usage > etc, but cpu percentages may be quite artificial, and you wouldn''t be able > to see real hardware bottlenecks without examining the other domains. > > > ------------------------------ > > *From:* xen-users-bounces@lists.xensource.com [mailto: > xen-users-bounces@lists.xensource.com] *On Behalf Of *Edoardo Ceccarelli > *Sent:* April 11, 2008 8:39 PM > *To:* xen-users@lists.xensource.com > *Subject:* [Xen-users] SAR in dom0 or domU > > > > Hello, > > I was wondering about sar under xen: is it more logical to install it on > dom0 or in each domU? > about disk i/o it should be able to give disk throughputs even in a dom0, > and maybe, also about cpu usage, memory, etc. > > certanly installing sar in a domU will give those values, but will this be > reliable? > > what''s your opinion about this? > > -- > Edoardo > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users >-- Edoardo Ceccarelli - eddy@axa.it _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
I would assume that would be domU territory, unless somebody can provide any
other means to gather that information.
If your system is reliable and you haven''t had any wall clock issues in
your
domains, it *should* be accurate, however I cannot confirm this (I''m
not
even sure how I would). There were various wall clock problems (read: time
went backwards, fast clocks, etc) in domains in 3.0.x under certain
conditions, I believe that these have been fixed in 3.1/3.2 xen releases
(some patches for clock issues were submitted, and no recent bug reports I
have found).
Also, independent wallclock might (this is tentative, I''m not sure if
domU
clocks are generated on timer interrupts or when the domU resumes, the
former would be fine, the later would be bad) introduce it''s own odd
skew
with heavily loaded systems due to the irregular scheduling and updating of
the domU clocks. Leaving the default behaviour for clock synch should be
considered best practice in this case (and most cases for that matter).
So in short, for >3.0.x, with independent wallclock disabled (default
behaviour), yes.
>3.0.x, with independent wallclock enabled, maybe.
3.0.x, likely not on smp, maybe not regardless.
_____
From: ridleys@gmail.com [mailto:ridleys@gmail.com] On Behalf Of Edoardo
Ceccarelli
Sent: April 13, 2008 2:37 PM
To: [STD]Ein
Cc: xen-users@lists.xensource.com
Subject: Re: [Xen-users] SAR in dom0 or domU
The abstraction that Xen gives should be enough to give reliable values in
certain conditions, I was wondering about disk troughput for example:
using LVM the dom0 sar shouldn''t even be able to produce values cause
it
cannot mount the partition
on the other hand the xenU domain should give pretty reliable values... has
anybody tried to compare sar results on xen?
...about cpu''s, I completely agree with you
On Sun, Apr 13, 2008 at 5:38 PM, [STD]Ein <ein@anti-logic.com> wrote:
It depends on what information you are trying to obtain.
If you want information about real hardware (cpu usage, nic''s in dom0
etc)
installing in dom0 would be the best case. Installing in domU can give you
good info about individual domain specific memory, network, tty usage etc,
but cpu percentages may be quite artificial, and you wouldn''t be able
to see
real hardware bottlenecks without examining the other domains.
_____
From: xen-users-bounces@lists.xensource.com
[mailto:xen-users-bounces@lists.xensource.com] On Behalf Of Edoardo
Ceccarelli
Sent: April 11, 2008 8:39 PM
To: xen-users@lists.xensource.com
Subject: [Xen-users] SAR in dom0 or domU
Hello,
I was wondering about sar under xen: is it more logical to install it on
dom0 or in each domU?
about disk i/o it should be able to give disk throughputs even in a dom0,
and maybe, also about cpu usage, memory, etc.
certanly installing sar in a domU will give those values, but will this be
reliable?
what''s your opinion about this?
--
Edoardo
_______________________________________________
Xen-users mailing list
Xen-users@lists.xensource.com
http://lists.xensource.com/xen-users
--
Edoardo Ceccarelli - eddy@axa.it
_______________________________________________
Xen-users mailing list
Xen-users@lists.xensource.com
http://lists.xensource.com/xen-users
Edoardo Ceccarelli wrote:> The abstraction that Xen gives should be enough to give reliable values > in certain conditions, I was wondering about disk troughput for example: > using LVM the dom0 sar shouldn''t even be able to produce values cause it > cannot mount the partitionI use SAR on Dom0... I have LVM on top op MD. It shows correct results for all LVM block devices, whether or not they are mounted. In fact I had it spot a domain doing heavy I/O on its swap partition, caused by syslog-ng going nuts when the log disk was full. I think you already rules out CPU. Overall I''m pretty sure about the block device and (non-HVM attached) NIC values. Memory is scoped, so its per DomU. This is Xen 3.1.2 on Linux 2.6.18 (Gentoo). - Joris [snip] _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users