Correlated volume placement in a distributed block storage service

A computer-implemented method comprising:

• receiving a request of a client computing device to create a plurality of data volumes on a block-storage service, wherein the service includes a plurality of placement engines, each placement engine configured to obtain a subrequest corresponding to a subset of data volumes from the plurality of data volumes and to place, among hosts of the block-storage service, individual data volumes of the subset;
• identifying an expected correlation of operation of the plurality of volumes;
• determining, from at least a metric regarding the plurality of data volumes in aggregate, a candidate set size, the candidate set size indicating a minimum required number of hosts among which the subset of data volumes of each subrequest are to be distributed;
• determining that a total number of hosts, within a plurality of hosts configured to host data volumes of the block-storage service, available to host a data volume of the plurality of data volumes is less than the candidate set size;
• and
• notifying the client computing device that the request cannot be fulfilled.

A system comprising:

• a data store including computer-executable instructions;
• and
• one or more computing devices configured to execute the instructions to:
• receive a request of a client computing device to create a plurality of data volumes on a block-storage service, wherein the service includes a plurality of placement engines, each placement engine configured to obtain a subrequest corresponding to a subset of data volumes from the plurality of data volumes and to place, among hosts of the block-storage service, individual data volumes of the subset;
• identify an expected correlation of operation of the plurality of volumes;
• determine, from at least a metric regarding the plurality of data volumes in aggregate, a candidate set size, the candidate set size indicating a minimum required number of hosts among which the subset of data volumes of each subrequest are to be distributed;
• determine that a total number of hosts, within a plurality of hosts configured to host data volumes of the block-storage service, available to host a data volume of the plurality of data volumes is less than the candidate set size;
• and
• notify the client computing device that the request cannot be fulfilled.