XtreemFS Configuration

There are three core parts of XtreemFS system:

• osd - object storage data (actual data storage)
• mrc - meta data and replica catalog server (headers storage)
• dir - directory (directory service)

(Note: dir service is similar to 'mon' service in Ceph)

Debian Package Setup

It is recommended to have the Linux kernel 2.6.36 RC 7 (this is the October 2010 kernel).

Download and Install

We are using Ubuntu and the build process is described in detail at external: https://www.xtreemfs.org/quickstart.php

Download the following packages from external: https://www.xtreemfs.org/download.php?t=debs

• xtreemfs-backend_1.2.3_all.deb
• xtreemfs-server_1.2.3_all.deb
• xtreemfs-tools_1.2.3_all.deb
• xtreemfs-client_1.2.3_amd64.deb

Install the packages

$ dpkg -i xtreemfs-client-1.2.3.deb xtreemfs-server-1.2.3.deb xtreemfs-backend-1.2.3.deb

on all the machines (Note. You can only install xtreemfs-server on server machines and xtreemfs-client on client machines, but all machines need xtreemfs-backend and probably xtreemfs-tools).

For details see the single machine install & setup. external https://www.xtreemfs.org/quickstart.php?t=d

XtreemFS Server

General note: very important to follow step by step;

Create a directory for OSDs at

 /var/lib/xtreemfs/objs/ 

4 Nodes

• s1 - osd0 (s1)
  
• s2 - osd1 (s2)
  
• s3 - mrc (s3)
  
• s4 - dir (s4)
  

plus one additional node for client (in this case, we will use s4). All OSD, MRC and DIR should have the configuration file /etc/xos/xtreemfs/*.properties

• - dirconfig.properties (dir service)
• - mrcconfig.properties (mrc service)
• - osdconfig.properties (osd service)

Since the setup is configured using *.properties, except for the dir service (s4), both osd and mrc must have their respective property file changed to point to the location (IP or hostname) of dir,

• For MRC (s3), edit /etc/xos/xreemfs/mrcconfig.properties, and change the default line dir_service.host = localhost to dir_service.host = s4
• For OSD1 and OSD2 (s1 and s2), edit /etc/xos/xreemfs/osdconfig.properties, and change the line dir_service.host = localhost to dir_service.host = s4

Also, you need to make sure you are mounting the OSDs in the correct location

• For OSD1 and OSD2, make sure to mount the device to "/var/lib/xtreemfs/objs/" as indicated in the line, object_dir = /var/lib/xtreemfs/objs/ It is recommended to mount ext3/ext4 file system.

Now, start up the servers (dir, mrc, osd). We recommned this order

   * /etc/init.d/xtreemfs-dir start 
   * /etc/init.d/xtreemfs-mrc start 
   * /etc/init.d/xtreemfs-osd start

Note that XtreemFS does not output any errors, so make sure to check the log messages

tail /var/log/xtreemfs/

Also use

ps -Af | grep xtreemfs

to check that the services are running.

See external https://www.xtreemfs.org/quickstart.php from more details.

XtreemFS Client

This part involves two steps:

1. Create a volume on the MRC-- e.g., Normal, Stripe (RAID0), Replica mode (Note. Volume location is always at mrc (s3).)
2. Mount the created volume (note - mount location is always at * dir (s4)*

Example (Basic FS)

1. Create FS called 'test' (you must create it to the MRC location)

$ sudo mkfs.xtreemfs s3/test

1. Mount the 'test' (you must mount it to the DIR location, and make sure to create empty directory at /media)

$ sudo mount.xtreemfs s4/test /media/test

Example (RAID-0 for osds on s1 and s2)

$ sudo mkfs.xtreemfs -p RAID0 -w 2 s3/raid

• -p accepts RAID0 only so far (1.2.x)
• -w is the 'width' i.e., how many OSDs are to be used for the striping (in round-robin fashion), in this case we have 2 OSDs.
• -s is the stripe-size in KB, by default it is 128K (e.g., -s 64 to set to 64KB)

Useful additional parameters for mounting

$ sudo mount.xtreemfs -o allow_other s4/raid /media/raid 

$ sudo mount.xtreemfs --cache-data --metadata-cache -o direct_io -o allow_other s4/raid /media/raid 

• --cache-data: enable client-side data caching
• --cache-metadata: enable client-side metadata caching
• -o (FUSE option): direct_io, allow_other, big_writes

For more information see

• external: https://www.xtreemfs.org/xtfs-guide-1.2.1/index.html
• man mount.xtreemfs
• man mkfs.xtreemfs

Check the current OSD configuration

Individual files can have its own file striping methods, e.g.,

$ sudo xtfs_sp --get /media/test
file:              /media/test
policy:            STRIPING_POLICY_RAID0
stripe-size (kB):  128
width:             1

Changing UUID

Each OSD/MRC/DIR must be uniquely identifiable by others.

For OSDs (in our case s1 and s2), each OSDs must have UUID.

./generate_uuid osdconfig.properties