# snapshot intro & applications
snapshot
backup_unit: index or cluster
incremental backup

Remote repository ways:
S3
HDFS
Azure
GCS
other platform, e.g.,shared file system, like NFS
not works on local FS, unless there's only one node to backup
https://discuss.elastic.co/t/why-snapshot-api-requires-shared-file-system/192612/5

Uses:
data backup
prod log to ai-cloud es
data migration