is where anyway to migrate from cassandra to scylladb without downtime?

[馬天一]

I have a cluster use cassandra 2.2.7. want to replace it with scylladb. is where anyway to migrate from cassandra to scylladb without downtime? 

or some tools that can transport data from cassandra to syclladb online. 

the way i can figure out is modify my codes to dual write to 2 dbs simultaneously. then export data from cassandra and import data into scylladb offline. when all of these done, switch datasource to the new scylladb.

is where a better way than this.

[Tzach Livyatan]

Hi

To migrate from Cassandra to Scylla without downtime you need to:

1. Start writing each request to both DBs (Cassandra and Scylla)

2. Migrate the data from the Cassandra sstable to Scylla(forklifting). You need to flush befoe migrating sstable. 

If you start 1 before 2, no data should be lost in the process. 

For step one above, you can either update your application to do a double write, or you I can grant you access to a beta tool, CQLProxy, as part of the scylla-enterprise project. CQLProxy basically doubles each write request for you. 

For the second part, you can use SSTableLoader, a tool which read SSTable and feeds them as CQL requests to Scylla.

Both tools, as well as a third tool which validate the two DBs are in sync are not part of Scylla 1.5, but as mentioned available as a closed beta. If you are interested, please let me know, I will be happy to share more info.

Regards

Tzach

 

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