Backups
Introduction
It is very important to note that backups are usually only 7 days old.
In the case of accidental deletions, you must inform immediately as it could take several days to load up the snapshot, consider that it is many TB in size.
What it entails
- A file system has to be created from the snapshot.
- this is loaded onto the SAN
- The SCSI bus needs to be rescanned
- this snapshot-rendered-to-filesystem must then be mounted.
scanning SCSI
root@marvin:/sys/class/scsi_host > rescan-scsi-bus.sh -a
Scanning SCSI subsystem for new devices
Scanning host 0 for SCSI target IDs 0 1 2 3 4 5 6 7, all LUNs
Scanning host 1 for SCSI target IDs 0 1 2 3 4 5 6 7, all LUNs
Scanning host 2 for SCSI target IDs 0 1 2 3 4 5 6 7, all LUNs
Scanning host 3 for SCSI target IDs 0 1 2 3 4 5 6 7, all LUNs
Scanning host 4 for SCSI target IDs 0 1 2 3 4 5 6 7, all LUNs
Scanning host 5 for SCSI target IDs 0 1 2 3 4 5 6 7, all LUNs
Scanning host 6 for all SCSI target IDs, all LUNs
Scanning for device 6 0 0 2 ...
OLD: Host: scsi6 Channel: 00 Id: 00 Lun: 02
Vendor: COMPELNT Model: Compellent Vol Rev: 0701
Type: Direct-Access ANSI SCSI revision: 05
Scanning for device 6 0 0 1 ...
OLD: Host: scsi6 Channel: 00 Id: 00 Lun: 01
Vendor: COMPELNT Model: Compellent Vol Rev: 0602
Type: Direct-Access ANSI SCSI revision: 05
Scanning for device 6 0 1 2 ...
OLD: Host: scsi6 Channel: 00 Id: 01 Lun: 02
Vendor: COMPELNT Model: Compellent Vol Rev: 0701
Type: Direct-Access ANSI SCSI revision: 05
Scanning for device 6 0 1 1 ...
OLD: Host: scsi6 Channel: 00 Id: 01 Lun: 01
Vendor: COMPELNT Model: Compellent Vol Rev: 0602
Type: Direct-Access ANSI SCSI revision: 05
Scanning host 7 for all SCSI target IDs, all LUNs
Scanning for device 7 0 6 1 ...
OLD: Host: scsi7 Channel: 00 Id: 06 Lun: 01
Vendor: COMPELNT Model: Compellent Vol Rev: 0602
Type: Direct-Access ANSI SCSI revision: 05
Scanning for device 7 0 6 2 ...
OLD: Host: scsi7 Channel: 00 Id: 06 Lun: 02
Vendor: COMPELNT Model: Compellent Vol Rev: 0701
Type: Direct-Access ANSI SCSI revision: 05
Scanning for device 7 0 7 1 ...
OLD: Host: scsi7 Channel: 00 Id: 07 Lun: 01
Vendor: COMPELNT Model: Compellent Vol Rev: 0602
Type: Direct-Access ANSI SCSI revision: 05
Scanning for device 7 0 7 2 ...
OLD: Host: scsi7 Channel: 00 Id: 07 Lun: 02
Vendor: COMPELNT Model: Compellent Vol Rev: 0701
Type: Direct-Access ANSI SCSI revision: 05
Scanning host 9 for SCSI target IDs 0 1 2 3 4 5 6 7, all LUNs
Scanning for device 9 2 0 0 ...
OLD: Host: scsi9 Channel: 02 Id: 00 Lun: 00
Vendor: LSI Model: MR9286-8e Rev: 3.29
Type: Direct-Access ANSI SCSI revision: 05
Scanning host 10 for SCSI target IDs 0 1 2 3 4 5 6 7, all LUNs
Scanning for device 10 2 0 0 ...
OLD: Host: scsi10 Channel: 02 Id: 00 Lun: 00
Vendor: LSI Model: MR9261-8i Rev: 2.13
Type: Direct-Access ANSI SCSI revision: 05
Scanning for device 10 2 1 0 ...
OLD: Host: scsi10 Channel: 02 Id: 01 Lun: 00
Vendor: LSI Model: MR9261-8i Rev: 2.13
Type: Direct-Access ANSI SCSI revision: 05
0 new or changed device(s) found.
0 remapped or resized device(s) found.
0 device(s) removed.
Background information
Jason Cormie of IT Services supplied the following details
The volume is raided across 348 disks (mix of SSD,SATA, SAS with 29 being hot spares), and asynchronously mirrored to our secondary datacentre in Maths.
Data scrubbing runs in the background regularly to detect any bad blocks, before they become an issue.
Snapshots for rollback are also mirrored to the secondary DC.
We can do synchronous mirroring, but it would have a performance impact as you’d have to wait for commits from the far side every time you wrote.
Note: synchronous mirroring is not enabled.
