Re: [lxc-users] LXD - Small Production Deployment - Storage

[Gabriel Marais]

On 2017/03/30 12:21 AM, Stéphane Graber wrote:

On Thu, Mar 30, 2017 at 12:01:14AM +0200, Gabriel Marais wrote:

On Wed, Mar 29, 2017 at 6:01 PM, Stéphane Graber 
wrote:


On Wed, Mar 29, 2017 at 03:13:36PM +0200, Gabriel Marais wrote:

Hi Guys

If this is the incorrect platform for this post, please point me in the
right direction.

We are in the process of deploying a small production environment with

the

following equipment:-

2 x Dell R430 servers each with 128GB Ram and 3 x 600GB SAS 10k drives
1 x Dell PowerVault MD3400 with
  3 x 600GB 15k SAS Drives
  3 x 6TB 7.2k Nearline SAS drives

The PowerVault is cabled directly to the Host Servers via Direct Attached
Storage, redundantly.


We would like to run a mixture of KVM and LXD containers on both Host
Servers.

The big question is, how do we implement the PowerVault (and to a certain
extent the storage on the Host Servers themselves) to be most beneficial

in

this mixed environment.

I have a few ideas on what I could do, but since I don't have much
experience with shared storage, I am probably just picking straws and

would

like to hear from others that probably has more experience than me.


Hi,

I'm not particularly familiar with the DELL PowerVault series, but it
looks like the other answers you've received so far have entirely missed
the "Direct Attached Storage" part of your description :)

For others reading this thread, this setup will effectively show up on
both servers as directly attached disks through /dev/mapper (because of
multipath), there is no need to use any kind of networked storage on top
of this.


The answer to your question I suspect will depend greatly on whether
you're dealing with a fixed number of VMs and containers, or if you
intend to spawn and delete them frequently. And also on whether you need
fast (no copy) migration of individual VMs and containers between the
two hosts.



We are not planning on having a fixed number of VMs and containers. It will
always grow as the requirement grow and as many as CPU and RAM will allow.
Migration of containers seem easy enough using the lxc migrate command,
although we have only done migrations with containers running on a normal
file system (e.g ext4) on a host.




One approach is to have a physical partition per virtual machine.



Meaning, to create physical partitions on the controller and assign it to
both hosts. So lets say we create a physical partitions on the controller,
60GB to be used for a specific VM. That partition will show up as e.g. sdd
on the host. We can then install the VM on that partition. If I understand
you correctly?


Correct, though you should use something more unique than sdd as those
device names are sequential based on detection order and so can change
after reboot. Since you're in a HA setup, you should have multiple paths
to each drive. Then something like multipathd will detect the different
paths and setup a virtual device in /dev/mapper for you to use. That
device is typically named after the WWN of the drive which is a unique
stable identifier that you can rely on.


With this, you can then access the drive from either host (obviously
never from both at the same time), which means that should you want to
start the VM on the other host, you just need to stop the kvm process on
one and start it again on the other, without any data ever being moved.



I assume we would simply use XML (export / import) to create the VM on the
other host which is pointing to the partition sitting on the storage device?


Yep


For containers, it's a bit trickier as we don't support using a raw
block device as the root of the container. So you'd need LXD to either
use the host's local storage for the container root and then mount block
devices into those containers at paths that hold the data you care
about. Or you'd need to define a block device for each server in the
PowerVault and have LXD use that for storage (avoiding using the local
storage).



I like the idea of creating a block device on the storage for each
container and have LXD use that block device for a specific container. I'm
not sure how and if we would be able to simply migrate a container from one
host to the other (assuming that we would have those block devices
available to both hosts)...?


Right so as I mentioned, you can't have a LXD container use a single
partition from your storage array as kvm lets you do.

So instead your best bet is probably to setup one chunk of storage for
use for the container root filesystems and point LXD to that as the
default storage pool.

For container data, you can then use a partition from your storage
array, format it and pass it to the LXD container with something like:

lxc config device add some-container mysql disk source=/dev/mapper/PARTITION 
path=/var/lib/mysql


The obvious advantage of the second option is that should one of the
server go away for whatever reason, you'd be able to mount that server's
LXD pool onto 

Re: [lxc-users] LXD - Small Production Deployment - Storage

[Stéphane Graber]

On Thu, Mar 30, 2017 at 12:01:14AM +0200, Gabriel Marais wrote:
> On Wed, Mar 29, 2017 at 6:01 PM, Stéphane Graber 
> wrote:
> 
> > On Wed, Mar 29, 2017 at 03:13:36PM +0200, Gabriel Marais wrote:
> > > Hi Guys
> > >
> > > If this is the incorrect platform for this post, please point me in the
> > > right direction.
> > >
> > > We are in the process of deploying a small production environment with
> > the
> > > following equipment:-
> > >
> > > 2 x Dell R430 servers each with 128GB Ram and 3 x 600GB SAS 10k drives
> > > 1 x Dell PowerVault MD3400 with
> > >   3 x 600GB 15k SAS Drives
> > >   3 x 6TB 7.2k Nearline SAS drives
> > >
> > > The PowerVault is cabled directly to the Host Servers via Direct Attached
> > > Storage, redundantly.
> > >
> > >
> > > We would like to run a mixture of KVM and LXD containers on both Host
> > > Servers.
> > >
> > > The big question is, how do we implement the PowerVault (and to a certain
> > > extent the storage on the Host Servers themselves) to be most beneficial
> > in
> > > this mixed environment.
> > >
> > > I have a few ideas on what I could do, but since I don't have much
> > > experience with shared storage, I am probably just picking straws and
> > would
> > > like to hear from others that probably has more experience than me.
> >
> > Hi,
> >
> > I'm not particularly familiar with the DELL PowerVault series, but it
> > looks like the other answers you've received so far have entirely missed
> > the "Direct Attached Storage" part of your description :)
> >
> > For others reading this thread, this setup will effectively show up on
> > both servers as directly attached disks through /dev/mapper (because of
> > multipath), there is no need to use any kind of networked storage on top
> > of this.
> >
> >
> > The answer to your question I suspect will depend greatly on whether
> > you're dealing with a fixed number of VMs and containers, or if you
> > intend to spawn and delete them frequently. And also on whether you need
> > fast (no copy) migration of individual VMs and containers between the
> > two hosts.
> >
> 
> We are not planning on having a fixed number of VMs and containers. It will
> always grow as the requirement grow and as many as CPU and RAM will allow.
> Migration of containers seem easy enough using the lxc migrate command,
> although we have only done migrations with containers running on a normal
> file system (e.g ext4) on a host.
> 
> 
> >
> > One approach is to have a physical partition per virtual machine.
> >
> 
> Meaning, to create physical partitions on the controller and assign it to
> both hosts. So lets say we create a physical partitions on the controller,
> 60GB to be used for a specific VM. That partition will show up as e.g. sdd
> on the host. We can then install the VM on that partition. If I understand
> you correctly?

Correct, though you should use something more unique than sdd as those
device names are sequential based on detection order and so can change
after reboot. Since you're in a HA setup, you should have multiple paths
to each drive. Then something like multipathd will detect the different
paths and setup a virtual device in /dev/mapper for you to use. That
device is typically named after the WWN of the drive which is a unique
stable identifier that you can rely on.

> > With this, you can then access the drive from either host (obviously
> > never from both at the same time), which means that should you want to
> > start the VM on the other host, you just need to stop the kvm process on
> > one and start it again on the other, without any data ever being moved.
> >
> 
> I assume we would simply use XML (export / import) to create the VM on the
> other host which is pointing to the partition sitting on the storage device?

Yep

> > For containers, it's a bit trickier as we don't support using a raw
> > block device as the root of the container. So you'd need LXD to either
> > use the host's local storage for the container root and then mount block
> > devices into those containers at paths that hold the data you care
> > about. Or you'd need to define a block device for each server in the
> > PowerVault and have LXD use that for storage (avoiding using the local
> > storage).
> >
> 
> I like the idea of creating a block device on the storage for each
> container and have LXD use that block device for a specific container. I'm
> not sure how and if we would be able to simply migrate a container from one
> host to the other (assuming that we would have those block devices
> available to both hosts)...?

Right so as I mentioned, you can't have a LXD container use a single
partition from your storage array as kvm lets you do.

So instead your best bet is probably to setup one chunk of storage for
use for the container root filesystems and point LXD to that as the
default storage pool.

For container data, you can then use a partition from your storage
array, format it and pass it to the LXD 

Re: [lxc-users] LXD - Small Production Deployment - Storage

[Gabriel Marais]

On Wed, Mar 29, 2017 at 6:01 PM, Stéphane Graber 
wrote:

> On Wed, Mar 29, 2017 at 03:13:36PM +0200, Gabriel Marais wrote:
> > Hi Guys
> >
> > If this is the incorrect platform for this post, please point me in the
> > right direction.
> >
> > We are in the process of deploying a small production environment with
> the
> > following equipment:-
> >
> > 2 x Dell R430 servers each with 128GB Ram and 3 x 600GB SAS 10k drives
> > 1 x Dell PowerVault MD3400 with
> >   3 x 600GB 15k SAS Drives
> >   3 x 6TB 7.2k Nearline SAS drives
> >
> > The PowerVault is cabled directly to the Host Servers via Direct Attached
> > Storage, redundantly.
> >
> >
> > We would like to run a mixture of KVM and LXD containers on both Host
> > Servers.
> >
> > The big question is, how do we implement the PowerVault (and to a certain
> > extent the storage on the Host Servers themselves) to be most beneficial
> in
> > this mixed environment.
> >
> > I have a few ideas on what I could do, but since I don't have much
> > experience with shared storage, I am probably just picking straws and
> would
> > like to hear from others that probably has more experience than me.
>
> Hi,
>
> I'm not particularly familiar with the DELL PowerVault series, but it
> looks like the other answers you've received so far have entirely missed
> the "Direct Attached Storage" part of your description :)
>
> For others reading this thread, this setup will effectively show up on
> both servers as directly attached disks through /dev/mapper (because of
> multipath), there is no need to use any kind of networked storage on top
> of this.
>
>
> The answer to your question I suspect will depend greatly on whether
> you're dealing with a fixed number of VMs and containers, or if you
> intend to spawn and delete them frequently. And also on whether you need
> fast (no copy) migration of individual VMs and containers between the
> two hosts.
>

We are not planning on having a fixed number of VMs and containers. It will
always grow as the requirement grow and as many as CPU and RAM will allow.
Migration of containers seem easy enough using the lxc migrate command,
although we have only done migrations with containers running on a normal
file system (e.g ext4) on a host.


>
> One approach is to have a physical partition per virtual machine.
>

Meaning, to create physical partitions on the controller and assign it to
both hosts. So lets say we create a physical partitions on the controller,
60GB to be used for a specific VM. That partition will show up as e.g. sdd
on the host. We can then install the VM on that partition. If I understand
you correctly?


> With this, you can then access the drive from either host (obviously
> never from both at the same time), which means that should you want to
> start the VM on the other host, you just need to stop the kvm process on
> one and start it again on the other, without any data ever being moved.
>

I assume we would simply use XML (export / import) to create the VM on the
other host which is pointing to the partition sitting on the storage device?


>
> For containers, it's a bit trickier as we don't support using a raw
> block device as the root of the container. So you'd need LXD to either
> use the host's local storage for the container root and then mount block
> devices into those containers at paths that hold the data you care
> about. Or you'd need to define a block device for each server in the
> PowerVault and have LXD use that for storage (avoiding using the local
> storage).
>

I like the idea of creating a block device on the storage for each
container and have LXD use that block device for a specific container. I'm
not sure how and if we would be able to simply migrate a container from one
host to the other (assuming that we would have those block devices
available to both hosts)...?


>
> The obvious advantage of the second option is that should one of the
> server go away for whatever reason, you'd be able to mount that server's
> LXD pool onto the other server and spawn a second LXD daemon on it,
> taking over the role of the dead server.
>

>From what I've read, a particular host can only use one ZFS Pool. This
creates a limitation since we won't be able to create two pools - 1 for the
faster storage drives and 1 for the slower storage drives.

My initial planning was to:-


Option 1

Take the Fast Storage (3 x 600GB 15k SAS drives) and configure them on the
controller as RAID5, split them into 2 and give each host a partition (sdx)
of +/- 600GB
Take the Slower Storage (3 x 6TB 7.2k drives) and configure them on the
controller as RAID5, split them into 2 and give each host a partition (sdy)
of +/- 6TB

Setup LVM with two volume groups, e.g. Vol0 - Fast Storage (300GB) and Vol1
(3TB) - Slow Storage
Create logical volumes as needed in terms of disk space per container and
VMs and install the container and VMs onto those logical volumes.


Option 2

Re: [lxc-users] LXD - Small Production Deployment - Storage

[Stéphane Graber]

On Wed, Mar 29, 2017 at 03:13:36PM +0200, Gabriel Marais wrote:
> Hi Guys
> 
> If this is the incorrect platform for this post, please point me in the
> right direction.
> 
> We are in the process of deploying a small production environment with the
> following equipment:-
> 
> 2 x Dell R430 servers each with 128GB Ram and 3 x 600GB SAS 10k drives
> 1 x Dell PowerVault MD3400 with
>   3 x 600GB 15k SAS Drives
>   3 x 6TB 7.2k Nearline SAS drives
> 
> The PowerVault is cabled directly to the Host Servers via Direct Attached
> Storage, redundantly.
> 
> 
> We would like to run a mixture of KVM and LXD containers on both Host
> Servers.
> 
> The big question is, how do we implement the PowerVault (and to a certain
> extent the storage on the Host Servers themselves) to be most beneficial in
> this mixed environment.
> 
> I have a few ideas on what I could do, but since I don't have much
> experience with shared storage, I am probably just picking straws and would
> like to hear from others that probably has more experience than me.

Hi,

I'm not particularly familiar with the DELL PowerVault series, but it
looks like the other answers you've received so far have entirely missed
the "Direct Attached Storage" part of your description :)

For others reading this thread, this setup will effectively show up on
both servers as directly attached disks through /dev/mapper (because of
multipath), there is no need to use any kind of networked storage on top
of this.


The answer to your question I suspect will depend greatly on whether
you're dealing with a fixed number of VMs and containers, or if you
intend to spawn and delete them frequently. And also on whether you need
fast (no copy) migration of individual VMs and containers between the
two hosts.

One approach is to have a physical partition per virtual machine.
With this, you can then access the drive from either host (obviously
never from both at the same time), which means that should you want to
start the VM on the other host, you just need to stop the kvm process on
one and start it again on the other, without any data ever being moved.

For containers, it's a bit trickier as we don't support using a raw
block device as the root of the container. So you'd need LXD to either
use the host's local storage for the container root and then mount block
devices into those containers at paths that hold the data you care
about. Or you'd need to define a block device for each server in the
PowerVault and have LXD use that for storage (avoiding using the local
storage).

The obvious advantage of the second option is that should one of the
server go away for whatever reason, you'd be able to mount that server's
LXD pool onto the other server and spawn a second LXD daemon on it,
taking over the role of the dead server.


-- 
Stéphane Graber
Ubuntu developer
http://www.ubuntu.com


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Re: [lxc-users] LXD - Small Production Deployment - Storage

[Tomasz Chmielewski]

On 2017-03-29 22:47, Marat Khalili wrote:
Just don't use NFS clients using NFS server on the same machine (same 
kernel), as this will break (hangs).

Huh? Works for me between LXC containers. Only had to tune
startup/shutdown sequence in systemd. In what exactly situation does
it hang? /worried/


Kernel deadlocks.

Note that you can have NFS client on machineA and NFS server on machineB 
- this is fine, it's two different kernels.


NFS client on machineA, and KVM guest with NFS server also on machineA 
is fine, too - two different kernels.



NFS client on machineA and NFS server on machineA, same kernel (as is 
the case with LXD) - will eventually deadlock.


The whole machine will not freeze out of the sudden, but you will notice 
you have more and more processes in D state, which you're not able to 
kill.



See for example:

https://lwn.net/Articles/595652/

It could be something improved in newer kernels, but I'm not aware of 
that.



If you need to export NFS-like mounts on the same server, you can use 
gluster mount, which is userspace - and which has poor performance, not 
really suitable for containers, but should be OK for i.e. large files 
accessed directly (no recursive find etc.).



Tomasz Chmielewski
https://lxadm.com
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Re: [lxc-users] LXD - Small Production Deployment - Storage

[Marat Khalili]

Just don't use NFS clients using NFS server on the same machine (same 
kernel), as this will break (hangs). 
Huh? Works for me between LXC containers. Only had to tune 
startup/shutdown sequence in systemd. In what exactly situation does it 
hang? /worried/



--

With Best Regards,
Marat Khalili

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Re: [lxc-users] LXD - Small Production Deployment - Storage

[Tomasz Chmielewski]

On 2017-03-29 22:13, Gabriel Marais wrote:

Hi Guys

If this is the incorrect platform for this post, please point me in
the right direction.

We are in the process of deploying a small production environment with
the following equipment:-

2 x Dell R430 servers each with 128GB Ram and 3 x 600GB SAS 10k drives
1 x Dell PowerVault MD3400 with
3 x 600GB 15k SAS Drives
3 x 6TB 7.2k Nearline SAS drives

The PowerVault is cabled directly to the Host Servers via Direct
Attached Storage, redundantly.


We would like to run a mixture of KVM and LXD containers on both Host 
Servers.


The big question is, how do we implement the PowerVault (and to a
certain extent the storage on the Host Servers themselves) to be most
beneficial in this mixed environment.

I have a few ideas on what I could do, but since I don't have much
experience with shared storage, I am probably just picking straws and
would like to hear from others that probably has more experience than
me.


NFS for LXD and iSCSI for KVM?

Just don't use NFS clients using NFS server on the same machine (same 
kernel), as this will break (hangs).



Tomasz Chmielewski
https://lxadm.com
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