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pstorage -> Virtuozzo Storage
'''Parallels Cloud Virtuozzo Storage''' (Pstorage) is a highly-available distributed storage (virtual SAN) with built-in replication and disaster recovery.
== Features ==
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[[File:Parallels_Cloud_Storage_is_a_software_defined_storage.png|300px|right|link=http://www.youtube.com/watch?v=6oEzW9w-1rg|Parallels Cloud Virtuozzo Storage is a software defined storage]]The main Pstorage Virtuozzo Storage features are listed below:
* No special hardware requirements. Commodity hardware (SATA/SAS drives, 1Gbit+ Ethernet) can be used to create a storage.
{{Warning|
* Parallels Cloud Virtuozzo Storage is available as a TECHNOLOGY PREVIEW ONLY for OpenVZ users and can't be licensed for production.* To unlock for running in production, you should upgrade to a full Parallels Cloud Server [[Virtuozzo]] product (see below).
* Maximum capacity limited for usage in technology preview mode is 100 GB of logical (usable by containers) disk space.
* After hitting this limit, writers can get blocked w/o errors expecting for a limit to be extended, so please avoid hitting the limit (it's not a bug :) ).
=== Components ===
[[File:Parallels_Cloud_Storage_components.png|650px|top|Parallels Cloud Virtuozzo Storage Components]]
Any Pstorage Virtuozzo Storage includes three components:
* Metadata server (MDS). MDSs manage metadata, like file names, and keep control over how files are split into chunks and where the chunks are stored. They also track versions of chunks and ensure that the cluster has enough replicas. An MDS can be run in multiple instances to provide high availability. Besides, MDSs keep a global log of important events that happen in the cluster.
* Chunk server (CS). A CS is a service responsible for storing real user data chunks and providing access to these data. A Pstorage cluster must have multiple instances of CSs for high availability.
* Clients. Clients access a Pstorage Virtuozzo Storage cluster by communicating with MDSs and CSs. Parallels Virtuozzo Containers and virtual machines can be run natively, i.e. directly from the Pstorage Virtuozzo Storage cluster. An additional Pstorage Virtuozzo Storage client - can be used to mount Pstorage Virtuozzo Storage as a conventional file system (though Pstorage is not POSIX-compliant). Besides, Pstorage files can be mounted as a block device using the "ploop" feature and formatted as ext4 file system for other needs.
A recommended cluster setup includes from 3 to 5 MDS instances (allowing you to survive the loss of 1 or 2 of MDSs, respectively) and multiple CSs providing storage capacity.
== Setup ==
This HOWTO explains how to setup Parallels Cloud Virtuozzo Storage (Pstorage) cluster and run OpenVZ containers stored there. Please note, that it's just a brief HOWTO for quick and easy evaluation of Parallels Cloud Virtuozzo Storage (configuring only 1x MDS and CS service) and is not a real manual. We highly recommend to consult [http://download.parallels.com/doc/pcs/pdf/Parallels_Cloud_Storage.pdf Pstorage manual] and man pages (such as pstorage, pstorage-make-cs, pstorage-make-mds etc.) as it contain a lot of important details on types of SSD drives supported, what are the recommended configurations, how to configure big clusters with failure domains and so on.
=== Installing Parallels Cloud Virtuozzo Storage software ===
In order to install Pstorage RPM packages, log in as root to all the machines planned to be added to the cluster and perform the following actions.
cat << EOF > /etc/yum.repos.d/pstorage.repo
[openvz-pstorage]
name=Parallels Cloud Virtuozzo Storage for OpenVZ
baseurl=http://download.openvz.org/pstorage/current
enabled=1
pstorage -c test_cluster make-mds -I -a 10.30.100.101 -r /pstorage/test_cluster-mds -p
This command creates new Parallels Cloud Virtuozzo Storage cluster and metadata server and configures the IP address of ''10.30.100.101'' for communication with this server (replace ''10.30.100.101'' with IP address of your own MDS server). MDS will store its data at location specified by '''-r''' option. The command will also ask you to enter the password for authentication in your cluster.
After you have created the MDS server, start the MDS management service ('''pstorage-mdsd''') and configure it to start automatically when the server boots:
The command will ask you the password that you specified when setting up the first MDS server.
Create the directory to mount the Parallels Cloud Virtuozzo Storage cluster to and then mount it as a conventional file system:
mkdir -p /pcs
Running a container over Pstrage is no different from any other local file system, so below example is just for the reference.
Log in to the computer running OpenVZ and that you have configured to act as a client for the Parallels Cloud Virtuozzo Storage cluster.
Load OpenVZ ploop kernel modules if they aren't loaded yet: