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Re: [PLUG] Need Troubleshooting Advice: Disk Errors in Virtual Machines
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On 09/21/2010 08:00 PM, Casey Bralla wrote:
On Tuesday 21 September 2010 7:25:26 pm Lee Marzke wrote:
On 09/21/2010 06:04 PM, Casey Bralla wrote:
I've got a weird problem which I hope somebody here can help me figure
out.
I'm running about a dozen virtual machines (mostly web servers) on a
triple- core AMD system running Debian Lenny (ie: "Stable"). Each of
the virtual machines is also running Debian Lenny.
I am having repeated disk errors on the Virtual Machines, but no disk
errors on the host machine. These disk errors often cause a Kernel
Panic within the VM, or otherwise crash the web server on the VM.
What are the specs on the host, memory, number/type of disks, vmware
server version
amount of RAM allocated to VM's and amount left over for the host.
Host Specs:
AMD Phenom Triple Core 2.4 GHz
ASRock Motherboad with AMD RS870L chipset
4 GBytes G.Skill RAM (2 DIMMS)
Debian Lenny
VMware Server 2.0.2 Build 203138
free reports:
total used free shared buffers cached
Mem: 3935036 3902036 33000 0 154324 2704932
-/+ buffers/cache: 1042780 2892256
Swap: 11807732 748 11806984
df -h reports:
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 576G 184G 363G 34% /
tmpfs 1.9G 0 1.9G 0% /lib/init/rw
udev 10M 748K 9.3M 8% /dev
tmpfs 1.9G 0 1.9G 0% /dev/shm
Most VM's given 64 MBytes RAM and 3 GByte SATA disks (which are fully
allocated when they are created)
Here's a mem and free from within a "typical" VM:
total used free shared buffers cached
Mem: 61480 58980 2500 0 26456 12560
-/+ buffers/cache: 19964 41516
Swap: 176672 540 176132
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 2.8G 676M 2.0G 25% /
tmpfs 31M 0 31M 0% /lib/init/rw
udev 10M 600K 9.5M 6% /dev
tmpfs 31M 0 31M 0% /dev/shm
64Mb per VM ? That seems way, way too low. The Debian
recommendation is 256Mb + what is needed by apache.
http://www.debian.org/releases/stable/i386/ch03s04.html.en
Most of my Ubuntu server VM's are allocated 1GB of RAM, but I run
zope/plone instances.
Is there some reason you have a dozen VM's ? Shouldn't apache handle
hundreds of websites on a single VM ?
Can I assume you have thousands of websites then ?
If you really have that many VM's you may need to re-think your
architecture somewhat. I don't think a
single disk system with 4GB of RAM is going to run a dozen VM's, that
system is barely good for 4 servers
servers. CPU usually doesn't matter, it's usually memory and then
disk I/O that are the issue. Here
I have a dual socket dual-core Opteron 265 SuperMicro MB, with 12GB
RAM, running ESXi 4.0
A single disk drive spindle just isn't going to do very well. Your OS
should be on one disk or flash drive and the VM's on an array.
You may want to use OpenFiler ( which is VMware certified ) with a
half-dozen or more disks mounted to your host over
NFS. And put the NFS traffic on a different NICS and separate LAN.
I use a Thecus N8800 NAS here.[1]
If this is production and you wish to stay with VMware, then you really
need to use ESXi instead of VM server.
ESXi is 64 bit, and allows you to add memory above 4Gb. With that
many VM's at 512Mb each plus overhead that's about
8GB memory required. Most ESX blades in data centers I've seen have
64GB or more RAM each.
ESX has a 60 day free trail, so you can evaluate this pretty easily
without cost if your server will boot ESX. The
Vmware converter will migrate the VM's you have easily into ESX.
I just gave a talk Monday at VMware user group on moving to ESXi [2],
that you might find interesting.
Lee
[1] http://plone.4aero.com/Members/lmarzke/thecus
[2]
http://plone.4aero.com/Members/lmarzke/vmug_esxi/moving-to-esxi-introduction/presentation_view
--
"Between subtle shading and the absence of light lies the nuance of iqlusion..." - Kryptos
Lee Marzke, lee@marzke.net http://marzke.net/lee/
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