Yes the single EBS volume will work. As long as a filesystem only spans a single EBS volume and in your case they all
sharethe same single EBS volume.
If each had there own volume; that too would work using multiple snapshots as one coherent backup.
i.e.
pg_start_backup()
take snapshot: /pgsql/pdbabe/data
take snapshot: /pgsql/pdbabe/tsdata
take snapshot: /pgsql/pdbabe/tsindex
take snapshot: /pgsql/pdbabe/tstemp
take snapshot: /pgsql/pdbabe/xlog
Pg_stop_backup()
And of course the associated WALs and future WALs.
