Guide · Servers
Backing up a file server: data, permissions and fast restores
In short: a file server is backed up from a snapshot so that open files are consistent with each other, and with all permissions so that the right people have access again after a restore. Incremental runs should only read what has changed. And since most requests concern individual files, what counts most is how quickly a file is back.
What is different about a file server
- Many people, many open files. Work carries on during the backup. Without a snapshot, half-saved files end up in the backup.
- Permissions are part of the data. Who may see which share and which folder is held in NTFS permissions or ACLs. If they are lost, the restore is only half done.
- Many files, little change. Hundreds of thousands of files, of which only a small part changes each day. A good incremental backup recognises this without reading every file again.
- A popular target for ransomware. An encrypted workstation also encrypts the shares through its network drives.
Backing up consistently
On Windows, the Volume Shadow Copy Service (VSS) provides a common point in time across all volumes involved – important when shares live on several volumes. On Linux, an LVM snapshot plays this role. If the server also runs an application with its own database, scripts before and after the snapshot briefly bring it into a safe state.
What must be backed up as well
| System | Besides the content |
|---|---|
| Windows | NTFS permissions, owner, attributes, timestamps, alternate data streams |
| Linux | Permissions, owner, timestamps, extended attributes with POSIX ACLs, symbolic and hard links |
Whatever does not need backing up should be excluded: page and hibernation files, temporary folders, recycle bins. That saves space and time without anything missing when it matters.
Spotting unusual changes early
A file server normally changes at a steady pace. If suddenly ten times as many files change as usual, or typical ransomware extensions appear in large numbers, that is a warning sign. The backup sees it first – and should not only report it but also prevent the last good restore points from being cleaned up under the normal rule. More on this in the guide Ransomware and backup.
How AegisGrid backs up file servers
AegisGrid backs up via VSS across all volumes involved on Windows and via an LVM snapshot (ext2/3/4, XFS) on Linux; without LVM it reads during operation and re-reads files that changed. Each profile allows up to 64 paths with exclusion patterns, and default exclusions are provided. Incremental runs take over unchanged files from the previous run; on Windows AegisGrid reads the changes from the USN journal. The data is deduplicated by content – also together with disk and VM backups in the same store – and encrypted before transfer. If a run stands out because of an unusual number of new, changed or deleted files, it is flagged, a notification goes out and older restore points stay protected for 30 days by default. Individual files are restored by searching across all restore points, see Restoring a deleted file.
Frequently asked questions about file server backup
File backup or a backup of the whole disk?
For a file server usually both: the file backup for restoring individual files quickly and with permissions, a disk or VM backup to restore the whole server after a failure. Thanks to deduplication, the second backup takes up hardly any extra space.
How often should a file server be backed up?
That depends on how much work may be lost at most (RPO). At least daily is common, several times a day where there is a lot of activity. Because incremental runs only read and store what has changed, even frequent runs are short.
Can I back up a NAS as a file server?
AegisGrid backs up the machines its agent runs on, that is Windows and Linux servers. With AegisGrid, a NAS serves as a destination for backups. If your shares are on a NAS, talk to us; in a pilot project we work out how best to cover your environment.
Back up your file server
In a pilot project we review shares, permissions and retention with you.