In the following the installation of a dCache
instance will be described. The Chimera name space provider,
some management components, and the SRM need a PostgreSQL server
installed. We recommend running this PostgreSQL on the local
node. The first section describes the configuration of a PostgreSQL
server. After that the installation of Chimera and of the
dCache components will follow. During the whole installation
process root access is required.
In order to install dCache the following requirements must be met:
An RPM-based Linux distribution is required for the following procedure. For Debian derived systems we provide Debian packages and for Solaris the Solaris packages or the tarball.
dCache requires Java 8 JRE. Please use the latest patch-level and check for upgrades frequently. It is recommended to use JDK as dCache scripts can make use of some extra features that JDK provides to gather more diagnostic information (heap-dump, etc). This helps when tracking down bugs.
PostgreSQL must be installed and running. We recommend the use of PostgreSQL version 9.2 (at least PostgreSQL version 8.3 is required).
Important
For good performance it is necessary to maintain and tune your PostgreSQL server. There are several good books on this topic, one of which is PostgreSQL 9.0 High Performance.
The RPM packages may be installed right away, for example using the command:
[root] #rpm -ivh dcache-2.14.0-1.noarch.rpm
The actual sources lie at http://www.dcache.org/downloads/IAgree.shtml. To install for example Version 2.14.0-1 you would use this:
[root] #rpm -ivh http://www.dcache.org/downloads/1.9/repo/2.14/dcache-2.14.0-1.noarch.rpm
The client can be found in the download-section of the above url, too.
Using a PostgreSQL server with dCache places a number of requirements on the database. You must configure PostgreSQL for use by dCache and create the necessary PostgreSQL user accounts and database structure. This section describes how to do this.
Install the PostgreSQL server with the tools of the operating system.
Initialize the database directory (for PostgreSQL version 9.2
this is /var/lib/pgsql/9.2/data/) , start the
database server, and make sure that it is started at system
start-up.
[root] #service postgresql-9.2 initdbInitializing database: [ OK ][root] #service postgresql-9.2 startStarting postgresql-9.2 service: [ OK ][root] #chkconfig postgresql-9.2 on
Perhaps the simplest configuration is to allow password-less access to the database and the following documentation assumes this is so.
To allow local users to access PostgreSQL without requiring a
password, ensure the file
pg_hba.conf, which (for PostgreSQL
version 9.2) is located in /var/lib/pgsql/9.2/data,
contains the following lines.
# TYPE DATABASE USER ADDRESS METHOD # "local" is for Unix domain socket connections only local all all trust # IPv4 local connections: host all all 127.0.0.1/32 trust # IPv6 local connections: host all all ::1/128 trust
Note
Please note it is also possible to run dCache with all PostgreSQL accounts requiring passwords. See the section called “Configuring Access to PostgreSQL” for more advice on the configuration of PostgreSQL.
Restarting PostgreSQL
If you have edited PostgreSQL configuration files, you must restart PostgreSQL for those changes to take effect. On many systems, this can be done with the following command:
[root] #service postgresql-9.2 restartStopping postgresql-9.2 service: [ OK ] Starting postgresql-9.2 service: [ OK ]
Chimera is a library providing a hierarchical name space
with associated meta data. Where pools in dCache store the
content of files, Chimera stores the names and meta data of
those files. Chimera itself stores the data in a relational
database. We will use PostgreSQL in this tutorial. The properties
of Chimera are defined in
/usr/share/dcache/defaults/chimera.properties.
See Chapter 4, Chimera for more information.
Create the Chimera database and user.
[root] #createdb -U postgres chimeraCREATE DATABASE[root] #createuser -U postgres --no-superuser --no-createrole --createdb --pwprompt chimeraEnter password for new role: Enter it again: You do not need to enter a password.
The dCache components will access the database server with the user srmdcache.
[root] #createuser -U postgres --no-superuser --no-createrole --createdb --pwprompt srmdcacheEnter password for new role: Enter it again: You do not need to enter a password.
Several management components running on the head node as well
as the SRM will use the database dcache
for storing their state information:
[root] #createdb -U srmdcache dcache
There might be several of these on several hosts. Each is used by the dCache components running on the respective host.
Create the database used for the billing plots.
[root] #createdb -O srmdcache -U postgres billing
And run the command dcache database update.
[root] #dcache database updatePnfsManager@dCacheDomain: INFO - Successfully acquired change log lock INFO - Creating database history table with name: databasechangelog INFO - Reading from databasechangelog many more like this...
Now the configuration of Chimera is done.
Before the first start of dCache replace the file
/etc/dcache/gplazma.conf with an empty
file.
[root] #mv /etc/dcache/gplazma.conf /etc/dcache/gplazma.conf.bak[root] #touch /etc/dcache/gplazma.conf
dCache can be started now.
[root] #dcache startStarting dCacheDomain done
So far, no configuration of dCache is done, so only the predefined domain is started.
dCache consists of one or more domains. A domain in dCache is a Java Virtual Machine hosting one or more dCache cells. Each domain must have a name which is unique throughout the dCache instance and a cell must have a unique name within the domain hosting the cell.
A service is an abstraction used in the dCache configuration to describe atomic units to add to a domain. It is typically implemented through one or more cells. dCache keeps lists of the domains and the services that are to be run within these domains in the layout files. The layout file may contain domain- and service- specific configuration values. A pool is a cell providing physical data storage services.
In the setup of dCache, there are three main places for configuration files:
/usr/share/dcache/defaults/etc/dcache/dcache.conf/etc/dcache/layouts
The folder /usr/share/dcache/defaults
contains the default settings of the dCache. If one of
the default configuration values needs to be changed, copy
the default setting of this value from one of the files in
/usr/share/dcache/defaults to
the file /etc/dcache/dcache.conf,
which initially is empty and update the value.
Note
In this first installation of dCache your dCache
will not be connected to a tape sytem. Therefore please
change the values for
pnfsmanager.default-retention-policy and
pnfsmanager.default-access-latency in the file
/etc/dcache/dcache.conf.
pnfsmanager.default-retention-policy=REPLICA pnfsmanager.default-access-latency=ONLINE
Layouts describe which domains to run on a host and which
services to run in each domain. For the customized
configuration of your dCache you will have to create a
layout file in /etc/dcache/layouts. In
this tutorial we will call it the
mylayout.conf file.
Important
Do not update configuration values in the files in the defaults folder, since changes to these files will be overwritten by updates.
As the files in /usr/share/dcache/defaults/ do
serve as succinct documentation for all available
configuration parameters and their default values it is
quite useful to have a look at them.
Domains and services are defined in the layout files. Depending on your site, you may have requirements upon the doors that you want to configure and domains within which you want to organise them.
A domain must be defined if services are to run in that domain. Services will be started in the order in which they are defined.
Every domain is a Java Virtual Machine that can be started and stopped separately. You might want to define several domains for the different services depending on the necessity of restarting the services separately.
The layout files define which domains to start and which services to put in which domain. Configuration can be done per domain and per service.
A name in square brackets, without a
forward-slash (/) defines a domain. A
name in square brackets with a
forward slash defines a service that is to run in a
domain. Lines starting with a hash-symbol
(#) are comments and will be ignored by
dCache.
There may be several layout files in the layout directory,
but only one of them is read by dCache when starting
up. By default it is the single.conf.
If the dCache should be started with another layout file
you will have to make this configuration in
/etc/dcache/dcache.conf.
Example:
dcache.layout=mylayoutThis entry in
/etc/dcache/dcache.conf will
instruct dCache to read the layout file
/etc/dcache/layouts/mylayout.conf
when starting up.
Example:
These are the first lines of
/etc/dcache/layouts/single.conf:
dcache.broker.scheme=none [dCacheDomain] [dCacheDomain/admin] [dCacheDomain/poolmanager]
[ defines a domain
called dCacheDomain]dCacheDomain. In this example only one domain
is defined. All the services are running in that
domain. Therefore no messagebroker is needed, which is
the meaning of the entry
messageBroker=none.
[
declares that the dCacheDomain/admin]admin service is to be run in
the dCacheDomain domain.
Example:
This is an example for the mylayout.conf file of a single node
dCache with several domains.
[dCacheDomain] [dCacheDomain/topo] [dCacheDomain/info] [namespaceDomain] [namespaceDomain/pnfsmanager] [namespaceDomain/cleaner] [namespaceDomain/dir] [poolmanagerDomain] [poolmanagerDomain/poolmanager] [adminDoorDomain] [adminDoorDomain/admin] [httpdDomain] [httpdDomain/httpd] [httpdDomain/billing] [gPlazmaDomain] [gPlazmaDomain/gplazma]
Note
If you defined more than one domain, a messagebroker is
needed, because the defined domains need to be able to
communicate with each other. This means that if you use
the file single.conf as a template
for a dCache with more than one domain you need to
delete the line
messageBroker=none. Then the default
value will be used which is
messageBroker=cells, as defined in
the defaults
/usr/share/dcache/defaults/dcache.properties.
dCache will need to write the files it keeps in pools. These pools are defined as services within dCache. Hence, they are added to the layout file of your dCache instance, like all other services.
The best way to create a pool, is to use the dcache script and restart the domain the pool runs in. The pool will be added to your layout file.
[<domainname>/pool]
name=<poolname>
path=/path/to/pool
pool.wait-for-files=${path}/data
The property pool.wait-for-files instructs the
pool not to start up until the specified file or directory
is available. This prevents problems should the underlying storage be unavailable (e.g., if a
RAID device is offline).
Note
Please restart dCache if your pool is created in a domain that did not exist before.
Example:
[root] #dcache pool create /srv/dcache/p1 pool1 poolDomainCreated a pool in /srv/dcache/p1. The pool was added to poolDomain in file:/etc/dcache/layouts/mylayout.conf.
In this example we create a pool called pool1 in the directory /srv/dcache/p1.
The created pool will be running in the domain poolDomain.
Mind the Gap!
The default gap for poolsizes is 4GiB. This means you should make a bigger pool than 4GiB otherwise you would have to change this gap in the dCache admin tool. See the example below. See also the section called “The Admin Interface”.
(local) admin >cd <poolname>(<poolname>) admin >set gap 2G(<poolname>) admin >save
Adding a pool to a configuration does not modify the pool or the data in it and can thus safely be undone or repeated.
Restart dCache to start the newly configured components
dcache restart and
check the status of dCache with
dcache status.
Example:
[root] #dcache restartStopping dCacheDomain 0 1 done Starting dCacheDomain done Starting namespaceDomain done Starting poolmanagerDomain done Starting adminDoorDomain done Starting httpdDomain done Starting gPlazmaDomain done Starting poolDomain done[root] #dcache statusDOMAIN STATUS PID USER dCacheDomain running 17466 dcache namespaceDomain running 17522 dcache poolmanagerDomain running 17575 dcache adminDoorDomain running 17625 dcache httpdDomain running 17682 dcache gPlazmaDomain running 17744 dcache poolDomain running 17798 dcache
Now you can have a look at your dCache via The Web
Interface, see the section called “The Web Interface for Monitoring dCache”:
http://<httpd.example.org>:2288/,
where <httpd.example.org> is the node on which your
httpd service is running.
For a single node dCache this is the machine on which your dCache is running.
By default the Java heap size and the maximum direct buffer size are defined as
dcache.java.memory.heap=512m dcache.java.memory.direct=512m
Again, these values can be changed in
/etc/dcache/dcache.conf.
For optimization of your dCache you can define the Java heap size in the layout file separately for every domain.
Example:
[dCacheDomain] dcache.java.memory.heap=2048m dcache.java.memory.direct=0m ... [utilityDomain] dcache.java.memory.heap=384m dcache.java.memory.direct=16m
Note
dCache uses Java to parse the configuration files and
will search for Java on the system path first; if it is
found there, no further action is needed. If Java is not
on the system path, the environment variable
JAVA_HOME defines the location of the Java
installation directory. Alternatively, the environment
variable JAVA can be used to point to the
Java executable directly.
If JAVA_HOME or JAVA cannot be
defined as global environment variables in the operating
system, then they can be defined in either
/etc/default/dcache or
/etc/dcache.env. These two files are
sourced by the init script and allow
JAVA_HOME, JAVA and
DCACHE_HOME to be defined.
Installing dCache on several nodes is not much more
complicated than installing it on a single node. Think about
how dCache should be organised regarding services and
domains. Then adapt the layout files, as described in the section called “Defining domains and services”, to the layout that you have in
mind. The files
/etc/dcache/layouts/head.conf and
/etc/dcache/layouts/pool.conf contain
examples for a dCache head-node and a dCache pool
respectively.
Important
You must configure a domain called dCacheDomain but the
other domain names can be chosen freely.
Please make sure that the domain names that you choose are unique. Having the same domain names in different layout files on different nodes may result in an error.
On any other nodes than the head node, the property dcache.broker.host
has to be added to the file /etc/dcache/dcache.conf. This property
should point to the host containing the special domain dCacheDomain, because that domain acts implicitly as a broker.
Tip
On dCache nodes running only pool services you do not need to install PostgreSQL. If your current node hosts only these services, the installation of PostgreSQL can be skipped.