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Per-shard sizing lets you adjust the VTTablet size of individual shards in a sharded Vitess keyspace instead of resizing the whole keyspace. A shard that takes more traffic can run more CPU and memory than the rest of the keyspace, and on Metal it can run more local storage. Enable per-shard sizing from the keyspace Shards tab, then set a size on any shard. Shards you don’t set keep the keyspace default.

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Eligibility

Per-shard sizing is available on a Vitess keyspace that:
  • Has two or more shards, all covering equal key ranges. A four-shard keyspace named -40, 40-80, 80-c0, c0- is eligible. One named -80, 80-c0, c0-, where the first shard covers half the keyspace and the others cover a quarter each, is not.
  • Is not imported or external
If Enable per-shard sizing is not shown on the Shards tab, the keyspace is not eligible. You cannot enable per-shard sizing while a keyspace resize or deploy request is in progress.

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Enable per-shard sizing

Enabling per-shard sizing is metadata only. Existing key ranges, VSchema, routing, and the keyspace default cluster size stay the same until you resize a shard.
1
In the PlanetScale dashboard, open the Vitess database and select the branch.
2
Open the keyspace and go to the Shards tab.
3
Click Enable per-shard sizing. The dialog confirms the shard count and default size, for example: “This keyspace has N shards with a default size of PS-X. Once enabled you will be able to adjust the sizes of individual shards.”
4
Confirm. You can then set sizes on individual shards, or leave shards on the keyspace default.

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Resize a shard

After per-shard sizing is enabled, resize a shard the same way you resize a keyspace: pick a cluster size and save. This changes the CPU, memory, and, on Metal, the local storage for that shard’s primary and replicas. Clearing a shard’s size returns it to the keyspace default. All shards in a keyspace must stay on the same storage class: all Metal or all network-attached storage. The size picker only lists sizes that match the keyspace storage class.

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Need help?

Get help from the PlanetScale Support team, or join our Discord community to see how others are using PlanetScale.