Scalability and Performance

How many servers can I join to a Parallels Cloud Storage cluster?

There is no strict limit on the number of servers you can include in a Parallels Cloud Storage cluster. However, you are recommended to limit the servers in the cluster to a single rack to avoid any possible performance degradation due to inter-rack communications.

How much disk space can a Parallels Cloud Storage cluster have?

A Parallels Cloud Storage cluster can support up to 8 PB of effective available disk space, which totals to 24 PB of physical disk space when 3 replicas are kept for each data chunk.

Can I add nodes to an existing Parallels Cloud Storage cluster?

Yes, you can dynamically add and remove nodes from a Parallels Cloud Storage cluster to increase its capacity or to take nodes offline for maintenance. For more information, see Adding and Replacing Chunk Servers .

What is the expected performance of a Parallels Cloud Storage cluster?

The performance depends on the network speed and the hard disks used in the cluster. In general, the performance should be similar to locally attached storage or better. You can also use SSD caching to increase the performance of commodity hardware by adding SSD drives to the cluster for caching purposes. For more information, see Using SSD Drives .

What performance should I expect on 1-gigabit Ethernet?

The maximum speed of a 1 GbE network is close to that of a single rotational drive. In most workloads, however, random I/O access is prevalent and the network is usually not a bottleneck. Research with large service providers has proved that average I/O performance rarely exceeds 20 MB/sec due to randomization. Virtualization itself introduces additional randomization as multiple independent environments perform I/O access simultaneously. Nevertheless, 10-gigabit Ethernet will often result in better performance and is recommended for use in production.

Will the overall cluster performance improve if I add new chunk servers to the cluster?

Yes. Since data is distributed among all hard drives in the cluster, applications performing random I/O experience an increase in IOPS when more drives are added to the cluster. Even a single client machine may get noticeable benefits by increasing the number of chunk servers and achieve performance far beyond traditional, locally attached storage.

Does performance depend on the number of chunk replicas?

Each additional replica degrades write performance by about 10%, but at the same time it may also improve read performance because the Parallels Cloud Storage cluster has more options to select a faster server.