Re: [CentOS-virt] KVM

[NightLightHosts Admin]

On Mon, Feb 8, 2016 at 2:53 PM, Alvin Starr  wrote:
> You need to provide more information.
> 20% is what number.
> There are something like 6 numbers on that line.
>
>

Post commands and results of command outputs
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Re: [CentOS-virt] LVM mirror database to ramdisk

[NightLightHosts Admin]

On Fri, Jan 22, 2016 at 11:02 AM, Ed Heron  wrote:
>   I'm still running CentOS 5 with Xen.
>
>   We recently replaced a virtual host system board with an Intel
> S1400FP4, so the host went from a 4 core Xeon with 32G RAM to a 6 core
> Xeon with 48G RAM, max 96G.  The drives are SSD.
>
>   I was recently asked to move an InterBase server from Windows 7 to
> Windows Server.  The database is 30G.
>
>   I'm speculating that if I put the database on a 35G virtual disk and
> mirror it to a 35G RAM disk, the speed of database access might improve.
>
>   I use local LVM for my virtual disks with DRBD on top to mirror the
> disk to a backup server.
>
>   If I change grub.conf to increase RAM disk size and increase host RAM,
> I could create a 35G RAM disk.
>
>   I'd modify rc.local to add
> pvcreate /dev/ramdisk
> vgextend vg /dev/ramdisk
> lvconvert -m 1 --corelog vg/lv_database /dev/ramdisk
>
>   Even with lv_database being 35G, it doesn't take long to activate the
> mirror.
>
>   I haven't decided where to put the commands to turn off the lvm
> mirror.
> lvconvert -m 0 vg/lv_database
> vgreduce vg /dev/ramdisk
> pvremove /dev/ramdisk
>
>   I haven't put this in real world use, yet.
>
>   On it's face, this might speed up database access.  Would we expect it
> to speed up database access in real world use?
>
>   Should I document the process so others could know how to do this?  I
> realize new documentation for CentOS 5 virtualization would be
> considered obsolete before I wrote it but I'm expecting to test CentOS 7
> virtualization in the next few months and, when I am comfortable, I'd
> upgrade my 18 virtual hosts.  I would update the documentation, at that
> time, as well.
>
>


I may not understand enough to understand what you are doing, you want
to actively mirror this with LVM or?
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Re: [CentOS-virt] LVM mirror database to ramdisk

[NightLightHosts Admin]

On Fri, Jan 22, 2016 at 4:54 PM, Ed Heron  wrote:
>   Yes, but it isn't that simple.  One copy of the mirror would be on a
> physical disk.  The other copy of the mirror would be on RAM disk.
> Since data in RAM doesn't generally survive reboot, the RAM piece would
> need to be turned off before shutdown and created on startup.
>
>> Is there something about LVM mirroring that can handle disks of
>> different speeds?
>
>   With newer LVM, there appears to be some settings that might help with
> that a bit.  With this older verion, I'd be hoping that the next
> available disk would handle each request.  If the physical disk takes
> longer to deal with the writes, the RAM disk might be the one that is
> available most of the time.
>
>   I'd much prefer a method of pre-filling a 35G cache but I saw a
> reference to creating a disk mirror in RAM and decided to explore it.
>

Can you post the results of your test when you get it working?
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Re: [CentOS-virt] LVM mirror database to ramdisk

[NightLightHosts Admin]

>  Ed Heron  wrote:
>   Yes, in a test environment, I am mirroring a Logical Volume with a RAM
> disk to increase the perceived speed of the disk.  I'm expecting to
> convert a live guest to this type of setup, this weekend.
>
>   I was asking 2 questions.
> 1. Should I expect a significant increase in speed in a real world
> environment?  With enough RAM, a good caching system will eventually do
> a similar function.  This is almost like pre-loading a cache.
> 2. Should I document the process for others?  I'm using CentOS 5 now,
> which is on it's way out, but I would update the documentation to
> include CentOS 7 when I upgrade my servers.
>

See this is where I was confused.  Would not the LVM mirror have to
sync all the time with the disk anyways?

Is there something about LVM mirroring that can handle disks of
different speeds?
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Re: [CentOS-virt] LVM mirror database to ramdisk

[NightLightHosts Admin]

Ed Heron  wrote:
>   Absolutely, I'll share my real world results.  I'm happy that I'm not
> the only person interested in the technique.  I'm a little disappointed
> somebody isn't telling me there is a much simpler method of putting my
> database in RAM.  The technique is only useful in a situation where the
> server has gobs of RAM so it might only apply to a small subset of users
> but it might speed up database access.  And since it is being done by
> the virtual host, the guest doesn't need to know anything about it.
> This keeps guest complexity down.  Also, I don't have as much Windows
> knowledge as I have Linux knowledge so it was easier for me to implement
> under Linux.


See,

This is where I get confused again, which type of database is it?
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Re: [CentOS-virt] win2008r2 update on centos 6 host made system unbootable

[NightLightHosts Admin]

On Tue, Dec 8, 2015 at 5:26 PM, Dennis Jacobfeuerborn
 wrote:
> Hi,
> today we ran into a strange problem: When performing a regular Windows
> 2008r2 update apparently among other things the following was installed:
> "SUSE - Storage Controller - SUSE Block Driver for Windows"
>
> Previously the disk drive was using the Red Hat virtio drivers which
> worked just fine but after the reboot after the update I just get a blue
> screen indicating that Windows cannot find a boot device.
>
> Does anyone understand what is going on here? Why is the windows update
> installing a Suse driver that overrides the Red Hat driver even though
> it is apparently incompatible with the system?
>
> Regards,
>   Dennis

Did you roll back the driver and did it work after that?
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Re: [CentOS-virt] Preferred method of provisioning VM images

[NightLightHosts Admin]

The world needs documentation bounties.


On Thu, Jun 12, 2014 at 4:30 PM, Peter pe...@pajamian.dhs.org wrote:

 -BEGIN PGP SIGNED MESSAGE-
 Hash: SHA1

 On 06/13/2014 03:47 AM, Dario Faggioli wrote:
  If you're up for it, Xen wiki will be glad to host it! :-P

 I would love to do a writeup on this, but my time is extremely limited
 right now.  I'll see what I can do.


 Peter
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 Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/

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Re: [CentOS-virt] Finally switching from Xen to KVM - question about networking

[NightLightHosts Admin]

Do you have the proper gateway/route configured on the VM?

On Wed, Jun 11, 2014 at 9:50 AM, Steve Campbell campb...@cnpapers.com wrote:

 On 6/10/2014 4:00 PM, Zoltan Frombach wrote:

 On 6/10/2014 9:51 PM, Steve Campbell wrote:
 On 6/10/2014 3:38 PM, Zoltan Frombach wrote:
 On 6/10/2014 9:27 PM, Steve Campbell wrote:
 On 6/10/2014 3:09 PM, Zoltan Frombach wrote:
 Steve,

 Try the following config.

 On your host:

 /etc/sysconfig/network-scripts/ifcfg-eth0:

 DEVICE=eth0
 BOOTPROTO=none
 ONBOOT=yes
 NM_CONTROLLED=no
 TYPE=Ethernet
 HWADDR=xx:xx:xx:xx:xx:xx- put your physical NIC's MAC address
 here
 BRIDGE=br0
 USERCTL=no
 IPV6INIT=no
 IPV6_AUTOCONF=no


 /etc/sysconfig/network-scripts/ifcfg-br0:

 DEVICE=br0
 BOOTPROTO=static
 ONBOOT=yes
 NM_CONTROLLED=no
 TYPE=Bridge
 IPADDR=10.0.5.16
 NETMASK=255.255.255.0   - you may need to adjust this to your
 network
 GATEWAY=10.0.5.1
 DNS1=8.8.8.8
 DNS2=8.8.4.4
 PEERDNS=yes
 DELAY=0
 STP=off
 USERCTL=no
 IPV6INIT=no
 IPV6_AUTOCONF=no


 Restart networking on the host.

 Then inside you VM:

 /etc/sysconfig/network-scripts/ifcfg-eth0:

 DEVICE=eth0
 BOOTPROTO=static
 ONBOOT=yes
 NM_CONTROLLED=no
 TYPE=Ethernet
 HWADDR=xx:xx:xx:xx:xx:xx- it must be a unique MAC address for
 your VM
 IPADDR=10.0.5.17
 NETMASK=255.255.255.0 - you may need to adjust this to your
 network
 GATEWAY=10.0.5.1
 DNS1=8.8.8.8
 DNS2=8.8.4.4
 PEERDNS=yes
 USERCTL=no
 IPV6INIT=no
 IPV6_AUTOCONF=no


 Then in Virtual Machine Manager make sure that your VM's NIC is
 connected to the br0 bridge, like this:

 Network Source: Specify shared device name
 Bridge Name: br0



 On 6/10/2014 8:16 PM, Steve Campbell wrote:
 On 6/10/2014 12:43 PM, Digimer wrote:
 On 10/06/14 12:38 PM, Steve Campbell wrote:
 On 6/10/2014 12:05 PM, Digimer wrote:
 On 10/06/14 11:46 AM, Steve Campbell wrote:
 On 6/10/2014 10:46 AM, Digimer wrote:
 On 10/06/14 10:03 AM, Steve Campbell wrote:
 I had so much trouble putting Centos 6 guest VMs on a Centos 5
 host
 that
 I finally switched to a Centos 6 host.

 I've not needed more that test VMs, so I've used Virtual
 Machine
 Manager
 on the old system, which worked pretty well, so I decided to
 create my
 first KVM guest machine. I noticed when I created it, I only
 had the
 options of NAT for my network interface, so I used that
 (obvious).

 Well, after starting the VM, I find I don't have connectivity
 with
 that
 interface. Reading, I find examples where I need to create
 bridges
 perhaps. Xen did most of this for me, so it's a little new to
 me.

 Can anyone throw me a clue, please?

 steve campbell
 Setting up a bridge is not that hard, and it will give your VMs
 direct
 access to the outside world, and host - VM access just
 fine as
 well.

 Here is a link showing how to setup a bridge connected to a
 bond
 device. Ignore the bond and pretend it is a straight ethX
 device:

 https://alteeve.ca/w/AN!Cluster_Tutorial_2#Configuring_our_Bridge.2C_Bonds_and_Interfaces








 The host has a device named virbr0 that is installed during
 system
 installation. It also has a network device vnet0. There are no
 files in
 /etc/sysconfig/network-scripts for these.

 Shouldn't I be able to use the virbr0 virtual bridge for this?
 I've
 tried setting up the VM's device with all of the options that is
 listed,
 but to no avail.

 Should I need to set up another bridge for this?

 And thanks for the link.

 steve
 virbr0 is created and managed by libvirtd. If you open Virtual
 Machine
 Manager, connect to localhost and then double-click on
 'localhost',
 you will see a tab for creating/managing bridges (NAT'ed,
 generally).
 I disable 'virbr0' as NAT'ing is generally not what I want.

 The 'vnetX' devices are dynamically created to link a VM's
 interface
 to a bridge. Think of them as virtual network cables. They get
 created
 and destroyed as needed.


 Sorry, but I'm confused:

 My host server has a real NIC and IP address with a real
 gateway to
 the
 outside:
 virtbr0 IP: 192.168.122.1
 Host IP: 10.0.5.16
 Gateway IP: 10.0.5.1
 on eth0 and this works

 My VM server has all fake stuff currently:
 Host IP: 10.0.5.17
 Gateway IP: 10.0.5.1
 on eth0 and this is like NIC without a cable.

 So I need to create a bridge device on both the host and VM (lets
 say I
 name it br1). I change the eth0 config file on both host and VM to
 point
 to br1 and give the br1 config file on both host and VM the
 correct
 IP.
 But won't this just let the two talk to each other. How will
 the VM
 server get outside?

 steve
 The bridge is created only on the host. Think of the bridge as
 being
 like a virtual switch. When a VM is created, you tell it to
 connect to
 the bridge, similar to how you would plug a physical wire into a
 real
 switch. That provides the link to the network, and then you
 configure
 the virtual server's network just as if it was a real network.

 On the host, you don't set the IP on the ethX device, instead you
 tell
 ethX to connect to the bridge 

Re: [CentOS-virt] Problem with X on VM

[NightLightHosts Admin]

What vnc are you using?

On Mon, Jun 9, 2014 at 9:40 AM, Steve Campbell campb...@cnpapers.com wrote:
 I've got a Centos 5 server with Xen installed. I'm trying to install a
 Centos 6.5 VM on it but once all is installed, the X window will not
 sync or display. I think I understand that it's probably due to the
 settings on the vnc stuff. I've got Centos 6.2 VMs that act just fine.

 Is there a way I can modify the VM's screen settings either during
 installation or after installation?

 Hope that makes sense. Thanks

 steve campbell
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Re: [CentOS-virt] Xen DomU supoprt in RHEL 7 and the CentOS Plan

[NightLightHosts Admin]

+3 XEN!

On Fri, May 23, 2014 at 3:56 AM, O'Reilly, Dan daniel.orei...@dish.com wrote:
 +2

 -Original Message-
 From: centos-virt-boun...@centos.org [mailto:centos-virt-boun...@centos.org] 
 On Behalf Of Antony Messerli
 Sent: Friday, May 23, 2014 7:49 AM
 To: centos-virt@centos.org
 Subject: Re: [CentOS-virt] Xen DomU supoprt in RHEL 7 and the CentOS Plan

 +1 on Xen support, I haven't had time to test on RHEL yet or poke around in 
 the kernel yet, but has all of the Xen support been removed from the kernel?

 Ant

 On May 23, 2014, at 8:31 AM, Kai Schaetzl mailli...@conactive.com wrote:

 Karanbir Singh wrote on Fri, 23 May 2014 13:19:45 +0100:

 so far, in rhel7rc its pretty clear that Xen instances ( domUs ) are
 not going to boot with the RHEL7rc kernel.

 What a pity. Not to mention Dom0.

 Wondering if someone has looked into what the challenges might be to
 enable this support, and then what the options are to deliver this support ?

 I'm sorry, I haven't yet, not even tested RHEL7rc. I just want to
 raise my hand and say, yes, I would like to have xen support if you
 can make it happen without too many hooplas. But I won't be able to help 
 much.

 Kai

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Re: [CentOS-virt] Xen and Centos 6.5

[NightLightHosts Admin]

I used it and it works great.  From what I remember I have to check
sometimes that the xen kernel is still default.  There is also a work
around for something but I need to access my local at home docs for
the info.



On Thu, May 22, 2014 at 12:18 PM, Carlos Vasquez
cvasq...@scratchspace.com wrote:
 On 5/22/2014 9:11 AM, Steve Campbell wrote:
 What exactly is the status of Xen and Centos 6.5?

 Is it available to install and run on production machines?

 I find a lot of how-to methods for installation on google, but is there
 a standard recommended way to install this according to the Centos folk?

 steve campbell

 Steve,
 I believe this is the currently recommended method:

 http://wiki.centos.org/HowTos/Xen/Xen4QuickStart

 --

 Regards,
Carlos

 -
 Carlos Vasquez
 Tech Support
 ScratchSpace, Inc.
 http://www.scratchspace.com/

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[CentOS-virt] Hey

[NightLightHosts Admin]

Just want to let you guys know that, although it may have been around
for a bit, bringing Xen back to CentOS is awesome and I really
appreciate it.  I was very disappointed when RedHat dropped support as
Xen is awesome.

Thanks for the effort!
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Re: [CentOS-virt] Hey

[NightLightHosts Admin]

I have used xen over kvm and others for a while.  It was what I just
started using first years ago.  With Xen I could manage domains and my
system seemed like a real server.  KVM just seemed like a command line
trick to me.  (I know it is not especially since its integration into
the kernel.)

xenserver is pretty sweet and there are some big products built around
it.  Citrix loves it too.  OpenStack is neat:
http://www.xenproject.org/presentations-and-videos/video/xpus13-rackspace.html

I was disappointed when redhat dropped xen :/  I mean now there is an
entire project around keeping xen on centos, etc.  This one.

In the end xen just seemed more strait forward.
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