[Xen-users] 4. Re: domU backup strategy (Simon Hobson)

["Felix du Plessis" <felix@xxxxxxxxxxxxxxxxx>]

Felix du Plessis

Tel:               +27 (0) 12 640 0135  
Fax:              +27 (0) 12 640 0151
Mobile:       +27 (0) 83 457 8718 


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Today's Topics:

   1. Re: libxl vs pygrub in 4.1.2 on rebooting domU (Ian Campbell)
   2. Re: Xen or KVM (Toens Bueker)
   3. Re: Xen or KVM (Toens Bueker)
   4. Re: domU backup strategy (Simon Hobson)
   5. Re: Xen or KVM (Luke S. Crawford)
   6. Re: xen 4.1 missing memory (Eduardo Bragatto)
   7. Re: Xen or KVM (TMC)
   8. Re: Xen or KVM (Ian Campbell)
   9. Alpine Linux Xen Dom0 LiveCD (Roger Pau Monne)
  10. Re: Alpine Linux Xen Dom0 LiveCD (Mark Schneider)


----------------------------------------------------------------------

Message: 1
Date: Thu, 17 May 2012 17:52:07 +0100
From: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
To: Dmitry Morozhnikov <dmiceman@xxxxxxx>
Cc: "xen-users@xxxxxxxxxxxxx" <xen-users@xxxxxxxxxxxxx>,        xen-devel
        <xen-devel@xxxxxxxxxxxxx>
Subject: Re: [Xen-users] libxl vs pygrub in 4.1.2 on rebooting domU
Message-ID: <1337273527.7781.109.camel@xxxxxxxxxxxxxxxxxxxxxx>
Content-Type: text/plain; charset="UTF-8"

On Wed, 2012-05-16 at 12:29 +0100, Dmitry Morozhnikov wrote:
> Hello, all.
> 
> There is a bug in 4.1.2, at least in gentoo. The question is if it 
> already fixed or not.
> 
> If someone issue reboot command from inside domU using pygrub 
> bootloader, then libxl, or more precisely, make_bootloader_args() in 
> libxl_bootloader.c will append parameters --kernel, --ramdisk and 
> --args on the second start. So, command line for the pygrub will look
like:
> 
> usr/bin/pygrub --kernel=/var/run/libxl/boot_kernel.KyI4aX
> --ramdisk=/var/run/libxl/boot_ramdisk.th_SXc
> --args=root=UUID=15c4dce6-e5fe-493f-b738-32b8e7ef829e ro console=hvc0 
> quiet  --output=/var/run/libxl/bl.nVj8nF/fifo --output-format=simple0 
> --output-directory=/var/run/libxl/ /var/xen/vs92.img
> 
> But that is completely wrong from the pygrub side! It bail out with:
> 
> Traceback (most recent call last):
>    File "/usr/bin/pygrub", line 783, in <module>
>      data = fs.open_file(chosencfg["kernel"]).read()
> IOError: [Errno 2] No such file or directory
> 
> Because there is no /var/run/libxl/boot_kernel.KyI4aX in inside of 
> domU disk image.

Right, this is definitely a bug. Thanks for reporting.

The problem is that the libxl bootloader infrastructure is updating the
caller provided domain configuration with the result of running the
bootloader, but this is only valid for the current guest, not the rebooted
version. Which means that when it gets re-used on reboot it all goes wrong.

As it happens xen-unstable does not suffer from this because it always
reparses the config file (and hence reinitialises the domain
configuration) on reboot.

However, that's a bit of a coincidence, and IMHO it is ugly for the libxl to
replace information in user supplied datastructures like this.
I have just proposed a patch to remove this trap.

Unfortunately the possibilities for fixing this in 4.1 are rather limited
since it doesn't provide the same level of infrastructure for doing this.

> Solution is simple, remove code to append this parameters:

That breaks the ability to use pygrub+kernel to boot a specific kernel from
the guest fs. I don't know if people use this functionality but I'd be
reluctant to remove it.

Ian.




------------------------------

Message: 2
Date: Thu, 17 May 2012 20:02:46 +0200
From: Toens Bueker <toens.bueker@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
To: xen-users@xxxxxxxxxxxxx
Subject: Re: [Xen-users] Xen or KVM
Message-ID: <20120517180246.GC22215@xxxxxxxxxxxxx>
Content-Type: text/plain; charset=iso-8859-1

Mark Schneider <ms@xxxxxxxxxxxxxxxxxxxxxx> wrote:

>    After playing for over a year with Xen (Xen/XCP/XenServer) and KVM I
>    tend now to use KVM due to low I/O performance of Xen/XCP/XenServer
>    when using HVM. PVMs in Xen have probably a bit better I/O-performance
>    but quite a lot of overhead to manage it with different operating
>    systems (I don't run any MS OS).

[...]

>    The free available version of XCP or XenServer has outdated templates
>    for HVM / PVMs and it looks like that Citrix doesn't really have
>    commercial interesst to improve them. I don't think that it will change
>    in the near future as most active Xen developers are working for
>    Citrix.
>    People like you, me and many others are a kind of unpaid Xen software
>    testers. I can myself invest some of time for testing of free software
>    products and help to impove them if I can use them without all the
>    licensing issues. I was even thinking about buying commercial XenServer
>    ... but due to high costs of the licenses and management costs I
>    decided simply to buy new hardware to have much better performance (DB
>    cluster applications) and more calculatlion power for the same price
>    and less administration overhead.

[...]

>    My current recomendation is currently KVM based on uBuntu 12.04. 

Actually I have slipped out of the "xen game" earlier on with the appearance
of kvm. Just because of the ease of having it in the mainline kernel.

I just wanted to support the other perspective to the discussion: Before
choosing between two hypervisor-based virtualization solutions you should
decide whether you could use os-based virtualization aka containers (with
openvz) instead. This would spare you a lot of hassle, which you subscribe
to by choosing a hypervisor-based solution. 

Even the best hypervisor on the newest hardware will not give you the I/O
(network- and storagewise), that an os-based virtualization will give you.

In my opinion, you should choose a solution, which will offer you "the best
of both worlds": OS-based virtualization for the mass of your VMs and
hypervisor-based virtualization for cases, containers can't cover.

That said, have a look at
 - Proxmox (http://www.proxmox.com/products/proxmox-ve) - openvz/kvm
 - SmartOS (http://smartos.org/) - solaris zones/kvm
 - Parallels Server Bare Metal
(http://www.parallels.com/products/server/baremetal/sp/)
 - does anybody know more solutions along those lines (maybe one including
xen)?

by
T?ns
--
There is no safe distance.



------------------------------

Message: 3
Date: Thu, 17 May 2012 20:16:18 +0200
From: Toens Bueker <toens.bueker@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
To: xen-users@xxxxxxxxxxxxx
Subject: Re: [Xen-users] Xen or KVM
Message-ID: <20120517181618.GD22215@xxxxxxxxxxxxx>
Content-Type: text/plain; charset=iso-8859-1

Andrew Wells <agwells0714@xxxxxxxxx> wrote:

>    Is it just for servers, then go xen, do you plan on doing VDI (windows)
>    then again xen has good solutions.
> 
>    Plan on doing Linux VDI look at Ovirt a kvm solution

I just wanted to throw Parallels into the ring here, as well. I don't
know how they compare to Citrix' solutions but one shouldn't forget,
that Parallels has containers for Windows, too. And - as far as I
understand - that makes it a compelling solution in combination with
Windows Datacenter Edition, regarding licensing.

http://www.netstream.co.il/fileadmin/groups/netstream/Testfolder/Doc/Paralle
ls_Virtualization_VDI.pdf

In terms of I/O they should beat all hypervisor-based solutions by far.

by
T?ns
-- 
There is no safe distance.



------------------------------

Message: 4
Date: Thu, 17 May 2012 19:22:09 +0100
From: Simon Hobson <linux@xxxxxxxxxxxxxxxx>
To: xen-users@xxxxxxxxxxxxx
Subject: Re: [Xen-users] domU backup strategy
Message-ID: <p06240813cbdaf0e91371@xxxxxxxxxxxxxxxxxxxxxx>
Content-Type: text/plain; charset="us-ascii" ; format="flowed"

>I've searched the group and googled for perfect backup solution

There is no such thing.

You'll see there have been a couple of "fairly vigorous" discussion 
of the subject in this list. Look for a thread called "Backup domU" 
from July last year - I think everything was "well discussed" then.

-- 
Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.



------------------------------

Message: 5
Date: Thu, 17 May 2012 19:00:42 -0400
From: "Luke S. Crawford" <lsc@xxxxxxxxx>
To: xen-users@xxxxxxxxxxxxx
Subject: Re: [Xen-users] Xen or KVM
Message-ID: <20120517230042.GC9360@xxxxxxxxxxxxxxxxxx>
Content-Type: text/plain; charset=us-ascii

On Thu, May 17, 2012 at 08:02:46PM +0200, Toens Bueker wrote:
> Mark Schneider <ms@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> I just wanted to support the other perspective to the discussion: Before
> choosing between two hypervisor-based virtualization solutions you
> should decide whether you could use os-based virtualization aka
> containers (with openvz) instead. This would spare you a lot of
> hassle, which you subscribe to by choosing a hypervisor-based solution. 

> Even the best hypervisor on the newest hardware will not give you the
> I/O (network- and storagewise), that an os-based virtualization will
> give you.
> 
> In my opinion, you should choose a solution, which will offer you "the
> best of both worlds": OS-based virtualization for the mass of your VMs
> and hypervisor-based virtualization for cases, containers can't cover.

The trouble I have with containers is that the compartmentalization?
is... much worse.   I rented FreeBSD jails before I moved to Xen,
and the Jails?  disk I/O was terrible.   I mean, total throughput
was great, far better than xen (I was using 10K disk, too)  - 
but disk IO would 'feel' slower for any particular user.

The thing is, with Xen?  the user gets his or her own pagecache.  If
they login once a week and check their mail and do nothing else?  their 
/etc/passwd /etc/shadow and their mail spool file  are all cached in ram.
The system feels very fast to the light user.   

With the Jails?   pagecache would be grabbed by the heavy user accessing
the disk a lot, so it always seemed slow for that light user.

So yeah; from my perspective?   Xen and KVM are both vastly easier
to administer than a container-based solution, as adaquate pagecache 
covers a multitude of sins.  

Of course, you are right about total/overall performance.   and in some
cases,
that's the important thing.   Containers are much lighter weight.   

I just wouldn't want to manage a container that I didn't have root
(and knowledge of what to kill) on.  Xen and KVM solve the worst of the
'heavy user making it suck for everyone' problem, and make it much
easier for me to limit them without any knowledge of what it's actually 
running when it doesn't automatically take care of it.  





------------------------------

Message: 6
Date: Fri, 18 May 2012 00:48:16 -0300
From: Eduardo Bragatto <eduardo@xxxxxxxxxxxx>
To: "Fajar A. Nugraha" <list@xxxxxxxxx>
Cc: Xen User-List <xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-users] xen 4.1 missing memory
Message-ID:
        <CAGUKMpjp__eRt6JhYFQpj3iwyfROmMgQTMZ+wkG7K417jgiOhw@xxxxxxxxxxxxxx>
Content-Type: text/plain; charset="iso-8859-1"

Hello Fajar,

I know this is an old thread, but I have a similar question and unlike the
guys who were ignoring your advice, I actually did everything I believe to
be necessary to control the usage of RAM memory by dom0 -- and I still see
memory missing (precisely 279MB on four PowerEdge R710 servers running "2 x
E5620" with 24GB each).

This is my scenario:

0. I'm running Xen 3.4.3 (from GITCO repo's) and different kernel releases,
but all same version: 2.6.18 (from CentOS: kernel-xen-2.6.18-194.32.1.el5 ,
kernel-xen-2.6.18-238.9.1.el5 and kernel-xen-2.6.18-274.3.1.el5);

1. I have dom0_mem=512M on my boot parameters;

2. I have xend-config.xsp configured with: (dom0-min-mem 512) AND
(enable-dom0-ballooning no);

3. There are 4 different boxes and they all are missing precisely 279MB
immediately after boot, regardless of any VM running or not (besides Dom0,
of course);

Here are some examples:

[root@hypervisor01]# xm list ; xm info | grep mem
Name                                        ID   Mem VCPUs      State
Time(s)
Domain-0                                     0   512    16     r-----
1955257.4
Domain-1                                     10 23500    16     r-----
11442974.1
total_memory           : 24563
free_memory            : 272
node_to_memory         : node0:272
[root@hypervisor01~]# echo '512+23500+272' | bc ### adding Dom0 + Dom1 +
"free_memory" should give me the same number as "total_memory"
24284
[root@hypervisor01~]# echo '24563-24284' | bc ### however it doesn't, I'm
missing 279MB
279

And here, a hypervisor with no VMs running at all, just after a reboot:

[root@hypervisor02 ~]# xm list ; xm info | grep mem
Name                                        ID   Mem VCPUs      State
Time(s)
Domain-0                                     0   512    16     r-----
1195310.3
total_memory           : 24563
free_memory            : 23772
node_to_memory         : node0:23772
[root@hypervisor02 ~]# echo '512+23772' | bc ### Again, adding Dom0
"free_memory" should give me the same number as "total_memory"
24284
[root@hypervisor02 ~]# echo '24563-24284' | bc ### And again, I'm missing
279MB
279


Is there any explanation as to where those 279MB are going to?

To be honest, it doesn't bother me that much that I have just a bit more
than 1% of "total_memory" simply "disappearing", but the lack of an
explanation does take my sleep.

Any thoughts?

Kind regards,
Eduardo Bragatto


On Thu, Aug 18, 2011 at 3:34 AM, Fajar A. Nugraha <list@xxxxxxxxx> wrote:

> On Thu, Aug 18, 2011 at 1:02 PM, Ian Tobin <itobin@xxxxxxxxxxxxx> wrote:
> > Hey,
> >
> > I set the dom0 min men to 512m in xend-config.sxp and ballooning is
> already enabled.  I rebooted and it initially shows 512m but one the vms
> are booted it drops to 256 .
> >
> > Any other thoughts?
>
> DISABLE ballooning?
>
> --
> Fajar
>
> _______________________________________________
> Xen-users mailing list
> Xen-users@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-users
>
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Message: 7
Date: Fri, 18 May 2012 19:32:16 +1000
From: TMC <tmciolek@xxxxxxxxx>
To: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
Cc: "xen-users@xxxxxxxxxxxxx" <xen-users@xxxxxxxxxxxxx>,        Andrew
        McGlashan <andrew.mcglashan@xxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-users] Xen or KVM
Message-ID:
        <CAA3FNtOroBYN92_UcnfM7VdnQL=2QsYy1MHLtFwTnsnk4nxd+Q@xxxxxxxxxxxxxx>
Content-Type: text/plain; charset="iso-8859-1"

I have had problems booting 32bit versions of XEN on 64 bit systems. Try
installing/booting 64bit dom0 and then building/booting some hosts...

Tomasz

On 17 May 2012 17:39, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:

> On Wed, 2012-05-16 at 19:30 +0100, Andrew McGlashan wrote:
> > I've had no help on the X3850 when I've asked questions here.
>
> If the machine fails to boot at all then this is very likely to be a bug
> rather than a misconfiguration, please do consider posting details to
> the xen-devel@ list if no help has been forthcoming here.
>
> If you do end up posting to xen-devel@ then collecting a log of the
> failed boot first would be very useful.
>
> Ian.
>
>
> _______________________________________________
> Xen-users mailing list
> Xen-users@xxxxxxxxxxxxx
> http://lists.xen.org/xen-users
>



-- 
--
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Message: 8
Date: Fri, 18 May 2012 11:09:23 +0100
From: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
To: TMC <tmciolek@xxxxxxxxx>
Cc: "xen-users@xxxxxxxxxxxxx" <xen-users@xxxxxxxxxxxxx>,        Andrew
        McGlashan <andrew.mcglashan@xxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-users] Xen or KVM
Message-ID: <1337335763.22316.45.camel@xxxxxxxxxxxxxxxxxxxxxx>
Content-Type: text/plain; charset="UTF-8"

On Fri, 2012-05-18 at 10:32 +0100, TMC wrote:
> I have had problems booting 32bit versions of XEN on 64 bit systems.
> Try installing/booting 64bit dom0 and then building/booting some
> hosts... 

That is always good advice if you have a 64 bit processor. The 64 bit
version of Xen is recommended over the 32 bit version if you have a 64
bit capable processor.

Note that you can run a 32 bit dom0 kernel (and userspace) on top of a
64 bit hypervisor if you like (so called "32on64"). Also with a 64 bit
hypervisor it is always possible to run either 32 or 64 bit guests
(regardless of the dom0 bit width).

Ian.

> 
> Tomasz
> 
> On 17 May 2012 17:39, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
>         On Wed, 2012-05-16 at 19:30 +0100, Andrew McGlashan wrote:
>         > I've had no help on the X3850 when I've asked questions
>         here.
>         
>         If the machine fails to boot at all then this is very likely
>         to be a bug
>         rather than a misconfiguration, please do consider posting
>         details to
>         the xen-devel@ list if no help has been forthcoming here.
>         
>         If you do end up posting to xen-devel@ then collecting a log
>         of the
>         failed boot first would be very useful.
>         
>         Ian.
>         
>         
>         _______________________________________________
>         Xen-users mailing list
>         Xen-users@xxxxxxxxxxxxx
>         http://lists.xen.org/xen-users
> 
> 
> 
> -- 
> --
> GPG key fingerprint: 3883 B308 8256 2246 D3ED  A1FF 3A1D 0EAD 41C4
> C2F0
> GPG public key available on pgp(dot)net key server





------------------------------

Message: 9
Date: Fri, 18 May 2012 11:33:18 +0100
From: Roger Pau Monne <roger.pau@xxxxxxxxxx>
To: "xen-devel@xxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxx>,
        xen-users@xxxxxxxxxxxxx
Subject: [Xen-users] Alpine Linux Xen Dom0 LiveCD
Message-ID: <4FB6256E.8070501@xxxxxxxxxx>
Content-Type: text/plain; charset="UTF-8"; format=flowed

Hello,

Alpine Linux has just released a Xen Dom0 LiveCD that contains a Linux 
Kernel 3.3.6 with PaX and grsec patches and Xen 4.1.2 with the CVE 
fixes. This LiveCD doesn't include any kind of X11 desktop, as it is 
intended for server use only.

The LiveCD is part of the Alpine Linux distribution, and will be updated 
every time there is an Alpine Linux release, ensuring that the users 
always get the latest versions of the software.

For those of you that don't know what Alpine Linux has to offer, here's 
a little extract from the Alpine Linux webpage:

Alpine Linux was designed with security in mind. It has proactive 
security features, such as PaX and SSP, that prevent security holes from 
being exploited.

Alpine Linux uses the uClibc C library and all of the base tools from 
BusyBox. These are normally found on embedded systems and are smaller 
than the tools found on GNU/Linux systems.

The traditional GNU/Linux base system is over 100MB in size (excluding 
the kernel), while the base system in Alpine Linux is only 4-5MB in size 
(excluding the kernel).

It's great for experimenting: Since the system configuration can be 
backed up to a single file, you will be able to test configurations 
before deploying them to production systems.

(You can find much more information on the Alpine Linux web page:
http://alpinelinux.org/about)

Also, Alpine Linux has the option to run from RAM, even when installed 
to a HDD or USB, allowing the user to save it's changes on a USB, floppy 
or other medium which then gets read at boot to leave the system as it 
was before the reboot. This is specially interesting for Xen Dom0, since 
it allows to have the whole system on RAM, which is immune to HDD 
crashes (you could have access to your Dom0 even after and HDD crash) 
and doesn't consume I/O resources.

This is still the first and experimental release of this LiveCD, so I 
would like to encourage Xen users to test it, and report back with the 
results.

The LiveCD can be found at: http://alpinelinux.org/downloads

Regards, Roger.



------------------------------

Message: 10
Date: Fri, 18 May 2012 13:47:21 +0200
From: Mark Schneider <ms@xxxxxxxxxxxxxxxxxxxxxx>
To: xen-users@xxxxxxxxxxxxx
Subject: Re: [Xen-users] Alpine Linux Xen Dom0 LiveCD
Message-ID: <4FB636C9.1080704@xxxxxxxxxxxxxxxxxxxxxx>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Am 18.05.2012 12:33, schrieb Roger Pau Monne:
> Hello,
>
> Alpine Linux has just released a Xen Dom0 LiveCD that contains a Linux 
> Kernel 3.3.6 with PaX and grsec patches and Xen 4.1.2 with the CVE 
> fixes. This LiveCD doesn't include any kind of X11 desktop, as it is 
> intended for server use only.
>
> The traditional GNU/Linux base system is over 100MB in size (excluding 
> the kernel), while the base system in Alpine Linux is only 4-5MB in 
> size (excluding the kernel).
> ...
> It's great for experimenting: Since the system configuration can be 
> backed up to a single file, you will be able to test configurations 
> before deploying them to production systems.
>
> ...
>
> Also, Alpine Linux has the option to run from RAM, even when installed 
> to a HDD or USB, allowing the user to save it's changes on a USB, 
> floppy or other medium which then gets read at boot to leave the 
> system as it was before the reboot. This is specially interesting for 
> Xen Dom0, since it allows to have the whole system on RAM, which is 
> immune to HDD crashes (you could have access to your Dom0 even after 
> and HDD crash) and doesn't consume I/O resources.
>
> This is still the first and experimental release of this LiveCD, so I 
> would like to encourage Xen users to test it, and report back with the 
> results.
>
> The LiveCD can be found at: http://alpinelinux.org/downloads

Roger,

Thanks a lot for this usefull image. I'm missing however a bootable USB 
image. We are already in 21st century and many new systems simply don't 
have CD/DVD drives anymore. Most of my servers run without it as I use 
*only* USB sticks as boot / install media instead of slow CD/DVD based 
images.

Best regards, Mark

-- 
ms@xxxxxxxxxxxxxxxxxxxxxx

http://rsync.it-infrastrukturen.org




------------------------------

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