1. What is hammer-backup?

This script operates HAMMER PFSes and dumps its contents for backup
purposes.

It uses mirror-read directive (see 'man 8 hammer') to perform a
dump to stdout that is redirected to a file with or without
compression.

It can take two types of backup:

  a) Full: Where ALL the data of the PFS is sent to a file.
  b) Inremental: It requires a previous full backup.

Additionally to the backup data itself, it creates a .bkp file
which contains metadata relative to the full and/or incremental
backups.

The format is the following

  filename,rsv01,rsv02,backup type,shared uuid,last TID,md5 hash

  filename   : Backup data file file.
  rsv01,rsv02: Reserved fields
  backup type: 1 or 2 (full or incremental, respectively)
  shared uuid: PFS shared UUID for mirror ops
  last TID   : Last transaction ID. Next incr. backup starting TID
  md5 hash   : For restoring purposes

Example:
  $ head -1 20140305222026_pfs_t1_full.xz.bkp
  20140305222026_pfs_t1_full.xz.bkp,,,f,e8decfc5-a4ab-11e3-942b-f56d04d293e0,000000011b36be30,05482d26644bd1e76e69d83002e08258

2. How to use it?

General usage.

Usage: hammer-backup [-h] [-v] [-i <full-backup-file>] [-f] [-c <compress-rate>] -d [<backup-dir>] <path-to-PFS>

 -h: Help outputo above.
 -v: Verbose
 -i <full-backup-file>: Incremental backup. Needs the full backup metadata file.
                        Relative path to -d
 -f: Full backup
 -c: Compress rate for xz(1)
 -d: Backup directory
 <path-to-PFS>: PFS path to backup

2.1 Performing a full backup

# ./hammer-backup -v -f -c 6 -d /root/backups /pfs/var
INFO: Full backup.
INFO: XZ compression level 6.
INFO: Backup directory is /root/backups.
INFO: Validating PFS
INFO: Initiating full backup
INFO: Launching: hammer -y -v mirror-read /pfs/var  2> /tmp/tmp.UdOwvYhv         | xz -c -6 > /root/backups/20140308001146_pfs_var.xz
INFO: Backup completed.

NOTE: -v is optional. Also note /pfs/var is found in standard installations.

2.2 Perform an incremental backup over a full one

First list the backups avail:

# ./hammer-backup -l -d /root/backups
20140308001146_pfs_var.xz.bkp:
 full: 20140308001146_pfs_var.xz endtid: 0x000000011db6dc20 md5: 303ee864f4a747d9da7d556e83b05de5

You can then specify the .bkp file you want. See the timestamp, and the path to
PFS separated by '_' are embedded to it.

# ./hammer-backup -c 6 -v -i 20140308001146_pfs_var.xz.bkp -d /root/backups /pfs/var
INFO: Incremental backup.
INFO: Backup directory is /root/backups.
INFO: Validating PFS
INFO: Initiating incremental backup
INFO: Launching: hammer -y -v mirror-read /pfs/var 0x000000011db6dc20 2> /tmp/tmp.AleUwNnA       | xz -c -6 > /root/backups/20140308002450_pfs_var.xz
INFO: Backup completed.

# ./hammer-backup -l -d /root/backups
20140308001146_pfs_var.xz.bkp:
 full: 20140308001146_pfs_var.xz endtid: 0x000000011db6dc20 md5: 303ee864f4a747d9da7d556e83b05de5
        incr: 20140308002450_pfs_var.xz endtid: 0x000000011db6e440 md5: 7a7c2799b880a293f2c8270c6a9b22aa

3.0 Recovering a PFS.

If you are very familiar with HAMMER you can do it manually, so following our
previous example:

 - Locate the backup we want to recover.
   # ./hammer-backup -l -d /root/backups
   20140308001146_pfs_var.xz.bkp:
    full: 20140308001146_pfs_var.xz endtid: 0x000000011db6dc20 md5: 303ee864f4a747d9da7d556e83b05de5
         incr: 20140308002450_pfs_var.xz endtid: 0x000000011db6e440 md5: 7a7c2799b880a293f2c8270c6a9b22aa

 - Mirror-write the files in the correct order. First the full, then the
   incremental ones. NOTE: -y on the hammer command will actually create
   a slave PFS.
   # unxz -c /root/backups/20140308001146_pfs_var.xz | hammer -y mirror-write /pfs/var_2
   PFS slave /pfs/var_2 does not exist. Auto create new slave PFS!
   Creating PFS #10        succeeded!
   /pfs/var_2
       sync-beg-tid=0x0000000000000001
       sync-end-tid=0x0000000000000001
       shared-uuid=ce020232-9a71-11e3-8278-f56d04d293e0
       unique-uuid=e569a0c9-a650-11e3-942b-f56d04d293e0
       slave
       label=""
       prune-min=00:00:00
       operating as a SLAVE
       snapshots directory defaults to /var/hammer/<pfs>
   Source can update synctid to 0x000000011db6dc20

 - Next, incremental ones:
   # unxz -c /root/backups/20140308002450_pfs_var.xz | hammer -y mirror-write /pfs/var_2
   Source can update synctid to 0x000000011db6e440

 - Once done, you can just upgrade the /pfs/var_2
   # hammer pfs-upgrade /pfs/var_2
   pfs-upgrade of PFS#10 () succeeded

For the example we used you have to make sure no process is using the current
/var PFS, and if none is you can just go ahead and unmount it. Afterwards you
can modify the symbolic link in /pfs to point to the restored one as needed.

4.0 Manipulating dumps

You can upload the .xz files and the .bkp files whenever you want, for example a
remote FTP server.