Replikasi XtreemFs

XtreemFS offers replication of all data. On the one hand, the Directory Service (DIR) and the Metadata Catalog (MRC) are replicated at database level. On the other hand, files are replicated on the OSDs with read/write or with read-only replication. In this chapter, we describe how these replication mechanisms work, their requirements and potential use-cases.

Pasted from <http://www.xtreemfs.org/xtfs-guide-1.5.1/index.html#tth_chAp6>

Konsekuensi dari replikasi adalah beban pada jaringan saat terjadi propagasi data antar server sehingga sebaiknya replikasi (dengan model read/write) hanya melibatkan maksimal 10 replika.

Dir dan Mrc juga dapat direplikasi. Saya pikir hal ini yang saya butuhkan dalam penelitian saya.

6.3  MRC and DIR Replication

Aside from file replication across OSDs, XtreemFS also supports MRC and DIR replication to increase data safety. MRC replication covers all file system metadata, whereas DIR replication covers configuration information of services as well as volumes.

6.3.1  Technical Details

DIR and MRC replication rely on the same principle as read-write replication of files. A primary replica, which is distinguished by means of a lease, accepts all updates and disseminates these to all backup replicas in the same order. When the primary fails, the lease will eventually expire and one of the former backup replicas can become primary. Unlike file replication, which may involve a different set of OSDs for each file, an MRC or DIR replicates its entire database. A replicated MRC or DIR consists of at least two individual server instances. Note that you will need three or more instances to be able to transparently recover from failures, as a majority of replicas always needs to be available to make progress.

Pasted from <http://www.xtreemfs.org/xtfs-guide-1.5.1/index.html#tth_chAp6>

To enable database replication across a set of DIR or MRC instances, it is necessary to enable replication and configure its parameters. This needs to be done prior to starting up the services. The basic steps are the following:

• Enable the replication plug-in on all replicated MRC/DIR instances
• Configure replication parameters across all instances
• Start up all replicated MRC/DIR instances

Pasted from <http://www.xtreemfs.org/xtfs-guide-1.5.1/index.html#tth_chAp6>

Teknik replikasi dapat dibaca pada URL referensi di atas. Cukup sederhana dan sepertinya dapat diikuti dengan mudah.