Any time you can get two for the price of one (a “2Fer”), you’re ahead of the game. By implementing our shared cache as a separate tier, you get (1) improved performance and (2) storage flexibility…a 2Fer.
What do I mean by storage flexibility? It means you can use enterprise storage, cloud storage or PC-based storage. Other shared-disk cluster databases require high-end enterprise storage like a NAS or SAN. This requirement was driven by the need for:
1. High-performance storage
2. Highly available storage
3. Multi-attach, or sharing data from a single volume of LUN across multiple nodes in the cluster.
Quite simply, you won’t see other shared-disk clustering databases using cloud storage or PC-based storage. However, the vast majority of MySQL users rely on PC-based storage, and most are not willing to pay the big bucks for high-end storage.
ScaleDB’s Cache Accelerator Server (CAS) enables users to choose the storage solution that fits their needs. See the diagram below:
Because all data is mirrored across paired CAS servers, it delivers high-availability, because if one fails the other continues running. Built-in recovery completes the HA solution. If you want further reassurance you can use a third CAS as a hot standby. This means that you can use the internal hard drives on your CAS on servers to provide highly-available storage.
The next post in this series on CAS will compare ScaleDB CAS, Network File System (NFS) and Cluster File System (CFS).
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