When we take a snapshot backup in Cassandra, it creates hard links to the existing SSTable files.

When a full compaction happens, the existing SSTable files are merged into new SSTable files.

So, what happens to the snapshot backup previously taken? Is the snapshot backup still valid?

$ cd <PATH TO CASSANDRA DATA DIRECTORY FOR KEYSPACE - MYKS AND TABLE - T1>

$ nodetool snapshot -t first_backup

$ ls -lrt
total 44
drwxr-xr-x 3 cassandra cassandra 4096 Jun 11 02:20 backups
-rw-r--r-- 2 cassandra cassandra  173 Jun 12 03:55 nb-15-big-Index.db
-rw-r--r-- 2 cassandra cassandra   32 Jun 12 03:55 nb-15-big-Filter.db
-rw-r--r-- 2 cassandra cassandra   62 Jun 12 03:55 nb-15-big-Summary.db
-rw-r--r-- 2 cassandra cassandra  776 Jun 12 03:55 nb-15-big-Data.db
-rw-r--r-- 2 cassandra cassandra    9 Jun 12 03:55 nb-15-big-Digest.crc32
-rw-r--r-- 2 cassandra cassandra   55 Jun 12 03:55 nb-15-big-CompressionInfo.db
-rw-r--r-- 2 cassandra cassandra 4879 Jun 12 03:55 nb-15-big-Statistics.db
-rw-r--r-- 2 cassandra cassandra   92 Jun 12 03:55 nb-15-big-TOC.txt
drwxr-xr-x 4 cassandra cassandra 4096 Jun 12 03:57 snapshots

$ cd <SNAPSHOT DIRECTORY FOR KEYSPACE - MYKS AND TABLE - T1>

$ ls -lrt
total 44
-rw-r--r-- 2 cassandra cassandra  173 Jun 12 03:55 nb-15-big-Index.db
-rw-r--r-- 2 cassandra cassandra   32 Jun 12 03:55 nb-15-big-Filter.db
-rw-r--r-- 2 cassandra cassandra   62 Jun 12 03:55 nb-15-big-Summary.db
-rw-r--r-- 2 cassandra cassandra  776 Jun 12 03:55 nb-15-big-Data.db
-rw-r--r-- 2 cassandra cassandra    9 Jun 12 03:55 nb-15-big-Digest.crc32
-rw-r--r-- 2 cassandra cassandra   55 Jun 12 03:55 nb-15-big-CompressionInfo.db
-rw-r--r-- 2 cassandra cassandra 4879 Jun 12 03:55 nb-15-big-Statistics.db
-rw-r--r-- 2 cassandra cassandra   92 Jun 12 03:55 nb-15-big-TOC.txt
-rw-r--r-- 1 cassandra cassandra 1012 Jun 12 03:57 schema.cql
-rw-r--r-- 1 cassandra cassandra   67 Jun 12 03:57 manifest.json

$ nodetool compact myks

$ cd <PATH TO CASSANDRA DATA DIRECTORY FOR KEYSPACE - MYKS AND TABLE - T1>

$ ls -lrt
total 44
drwxr-xr-x 3 cassandra cassandra 4096 Jun 11 02:20 backups
drwxr-xr-x 4 cassandra cassandra 4096 Jun 12 03:57 snapshots
-rw-r--r-- 1 cassandra cassandra  173 Jun 12 06:24 nb-16-big-Index.db
-rw-r--r-- 1 cassandra cassandra   32 Jun 12 06:24 nb-16-big-Filter.db
-rw-r--r-- 1 cassandra cassandra   62 Jun 12 06:24 nb-16-big-Summary.db
-rw-r--r-- 1 cassandra cassandra  776 Jun 12 06:24 nb-16-big-Data.db
-rw-r--r-- 1 cassandra cassandra    9 Jun 12 06:24 nb-16-big-Digest.crc32
-rw-r--r-- 1 cassandra cassandra   55 Jun 12 06:24 nb-16-big-CompressionInfo.db
-rw-r--r-- 1 cassandra cassandra 4879 Jun 12 06:24 nb-16-big-Statistics.db
-rw-r--r-- 1 cassandra cassandra   92 Jun 12 06:24 nb-16-big-TOC.txt

## After this compaction, is the above snapshot still valid? Can it be used for a restore?