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Many OpenVZ questions (software raid, development) [message #32455] Sat, 09 August 2008 05:19 Go to next message
dbmv is currently offline  dbmv
Messages: 3
Registered: August 2008
Junior Member
Hey guys,

I have a pretty long list of things that I need answered before I can go any further into the OpenVZ world of things.. I hope I can get the information needed and share back in some ways Smile


Alright, so let's get started :


Hardware
----

1) I plan to setup 2 SCSI disks in a Raid 1 array. The host machine is CentOS 5. Now, I know at setup of CentOS 5, you can setup software Raid 1 with the GUI, however, when you change the kernel to the OpenVZ stable, what needs to be done to resume Raid 1 mirroring? Any risks?

2) Same lines with soft raid 1/OpenVZ kernel : any known issues with it in CentOS 5? Software Raid 1 works great upon setup with CentOS, but I've heard through the grapevine that setting it up on OpenVZ is much harder, because the system is already running, and OpenVZ might not find the boot partition?

3) I'm just using a simple switch, with an ethernet drop from my provider, with a few IPs. Using the built-in ARP from OpenVZ, I want the IPs to be portable from all nodes (I.E not bound to any NIC). Will a simple switch handle this without configuration?

Software
----

1) Transfers of containers from one host node to another. I know there's the built-in utility that uses rsync for "almost no downtime" between nodes. However, SSH keys need to be installed for this to work correctly, right? Now I'm really rusty with this, but is this possible for server-to-server? I plan to write a PHP/MySQL app to control the containers, so SSH keys are needed for everything I assume.

2) I've been on Virtuozzo before, and during a container migration, during the last rsync stage, a page shows up on the IP, that says it's currently migrating. Does OpenVZ have this? If so, can it be edited?

3) On creation of the container, is it possible to run commands on it (ssh) to install a control panel, for example, send the status back to the php app, and only when the install is complete say that the install is complete? I assume this could be done by using a bash script and going line by line, but just wondering if there's a built-in utility

4) How's everyone handling backups? Do you just incrementally backup /etc/vz and /vz ? Is there some way to backup the individual containers + their configurations for easy restores? If so, any way to do so incremenally?

5) Ram usage. There's a pretty big discrepancy from Virtuozzo to OpenVZ, due to caching and its filesystem. Is there some way to get OpenVZ to report the "actual" memory usage, and not whatever is cached?


That's really it, like I said, I've been reading up on these forums and OpenVZ in general, and can only hope to share with others what I've picked up!

TIA!

[Updated on: Sat, 09 August 2008 05:20]

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Re: Many OpenVZ questions (software raid, development) [message #32463 is a reply to message #32455] Sun, 10 August 2008 17:54 Go to previous messageGo to next message
dbmv is currently offline  dbmv
Messages: 3
Registered: August 2008
Junior Member
bump?
Re: Many OpenVZ questions (software raid, development) [message #32464 is a reply to message #32455] Mon, 11 August 2008 05:51 Go to previous messageGo to next message
jonasb is currently offline  jonasb
Messages: 20
Registered: July 2007
Junior Member
Quote:


1) I plan to setup 2 SCSI disks in a Raid 1 array. The host machine is CentOS 5. Now, I know at setup of CentOS 5, you can setup software Raid 1 with the GUI, however, when you change the kernel to the OpenVZ stable, what needs to be done to resume Raid 1 mirroring? Any risks?



It should not be a problem.

Quote:


2) Same lines with soft raid 1/OpenVZ kernel : any known issues with it in CentOS 5? Software Raid 1 works great upon setup with CentOS, but I've heard through the grapevine that setting it up on OpenVZ is much harder, because the system is already running, and OpenVZ might not find the boot partition?



What id you heard? It should not be a problem. mdadm works.

Quote:


3) I'm just using a simple switch, with an ethernet drop from my provider, with a few IPs. Using the built-in ARP from OpenVZ, I want the IPs to be portable from all nodes (I.E not bound to any NIC). Will a simple switch handle this without configuration?



Yes.

Quote:


1) Transfers of containers from one host node to another. I know there's the built-in utility that uses rsync for "almost no downtime" between nodes. However, SSH keys need to be installed for this to work correctly, right? Now I'm really rusty with this, but is this possible for server-to-server? I plan to write a PHP/MySQL app to control the containers, so SSH keys are needed for everything I assume.



Yes SSH-keys are needed.

Quote:


2) I've been on Virtuozzo before, and during a container migration, during the last rsync stage, a page shows up on the IP, that says it's currently migrating. Does OpenVZ have this? If so, can it be edited?



A page? OpenVZ is only command line.

Quote:


3) On creation of the container, is it possible to run commands on it (ssh) to install a control panel, for example, send the status back to the php app, and only when the install is complete say that the install is complete? I assume this could be done by using a bash script and going line by line, but just wondering if there's a built-in utility



It's possible to run commands. Your controlpanel has to support command line install.

Quote:


4) How's everyone handling backups? Do you just incrementally backup /etc/vz and /vz ? Is there some way to backup the individual containers + their configurations for easy restores? If so, any way to do so incremenally?



Use any backup software you like. If you are unsure of data in memory (MySQL, etc) you can suspend the container before backup.

Quote:


5) Ram usage. There's a pretty big discrepancy from Virtuozzo to OpenVZ, due to caching and its filesystem. Is there some way to get OpenVZ to report the "actual" memory usage, and not whatever is cached?



Do you mean usage of a container? Its reported in /proc/user_beancounters.
Re: Many OpenVZ questions (software raid, development) [message #32465 is a reply to message #32455] Mon, 11 August 2008 05:59 Go to previous messageGo to next message
dbmv is currently offline  dbmv
Messages: 3
Registered: August 2008
Junior Member
Hi Jonas,

Thank you very much for your responses!


When you say command line control from the CP.. it would essentially be the same as when creating the container, correct?

Basically, it would create the container
enter
run commands
exit

correct? Or would a bash script be better since it goes line by line?



What I meant by the page.. Virtuozzo comes with an Apache client, which, during the last phase of a migration, shows an HTTP page to any websites resolving to the migrating container, that it is in the last stage of "maintenance" and that it will be up shortly.

Also, is there a tutorial somewhere to re-setup software raid 1 on a Centos 5 system for OpenVZ? Or does setting it up on CentOS setup take care of it, and installing the OpenVZ kernel won't matter?

[Updated on: Mon, 11 August 2008 06:02]

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Re: Many OpenVZ questions (software raid, development) [message #32466 is a reply to message #32465] Mon, 11 August 2008 06:10 Go to previous message
jonasb is currently offline  jonasb
Messages: 20
Registered: July 2007
Junior Member
Quote:


When you say command line control from the CP.. it would essentially be the same as when creating the container, correct?

Basically, it would create the container
enter
run commands
exit

correct? Or would a bash script be better since it goes line by line?



Yes, that should workr if the CP support the commands or the shell script. I think the most CPs requires some input from the user.

Quote:


What I meant by the page.. Virtuozzo comes with an Apache client, which, during the last phase of a migration, shows an HTTP page to any websites resolving to the migrating container, that it is in the last stage of "maintenance" and that it will be up shortly.



OpenVZ doesnt have a Apache client.


Quote:


Also, is there a tutorial somewhere to re-setup software raid 1 on a Centos 5 system for OpenVZ? Or does setting it up on CentOS setup take care of it, and installing the OpenVZ kernel won't matter?



Its enoug with the CentOS install. You just change kernel when you are using OpenVZ and the raid modules are there.
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