Arvados

Background: Currently keep-balance detects when a storage device like an S3 bucket is used by multiple keepstore servers, and arbitrarily chooses one of them to get the index. However, this relies on the "device ID" returned by keepstore, which is

• s3://endpoint/bucketname, if the volume is an S3 bucket
• block device UUID, if the volume is a local filesystem
• empty, if the volume is a network-mounted filesystem

When the device ID is empty, the volumes might be different, so keep-balance indexes all of them.

Now that each keepstore server uses the same configuration file, each configured volume has a unique UUID, and the volume UUID is returned in the list of mounts reported by keepstore (none of which were true when the "device ID" approach started), keep-balance should detect identical/duplicate mounts by comparing volume UUIDs instead of device IDs.

(Note this will confuse keep-balance if the config uses a single volume UUID to mount a local disk like "/data" on multiple keepstore machines. But the install docs explicitly describe not doing that, and it is not a kind of configuration we want to support. Worst outcome is that someone with this kind of wonky config would see a lot of blocks misreported as underreplicated or missing by keep-balance until they fix their config.)