User configuration 

Overview 

An administrator can change user account properties, Protected Item, Storage Vault, Device, and Policy settings via the Comet Server web interface.

A user can change their own Protected Item and Storage Vault settings via the Comet Backup application interface.

The descriptions in this section apply to both situations.

Profile 

Username 

Usernames must be at least six characters long, using only the characters a-z, A-Z, 0-9, underscore (_) and hyphen (-).

In Comet 17.9.0 and later, the additional characters @ and . are supported.

Usernames are case-sensitive.

Changes to username support 

Certain versions of Comet expanded the list of characters allowed in usernames. Usernames that are valid for newer versions of Comet may be invalid when used with older versions of Comet. This may impact certain scenarios including software downgrades and/or mixed-server-version replication.

If you have usernames that would be invalid under older versions of Comet, please take care to ensure that all your Comet infrastructure is upgraded past the point of conversion, to prevent any potential issues that may occur.

Future versions of Comet may allow characters from international alphabets in usernames (subject to Unicode normalization).

Password 

Passwords must be at least eight characters long.

The password must be on one line (no CR/LF bytes are permitted).

Any other characters are permitted, including spaces, special characters, symbols, and characters from international alphabets.

Language 

The user is able to set their own language.

As of Comet 17.9.2, the following languages are supported:

Language First introduced
English
Spanish Comet Beta 1.0.0
Brazilian Portuguese Comet 17.3.2
Dutch Comet 17.3.4
Italian Comet 17.9.0
German Comet 17.9.2
French Comet 17.9.2

Timezone 

The Comet Backup app resets the user's timezone automatically, to match the user's operating system timezone. An administrator can set the timezone to any valid IANA tzdata timezone. The default timezone for new accounts is always Etc/UTC.

Email addresses 

Comet Server has some built-in features to send email reports to customers. You can configure any number of email addresses for a user account.

In Comet 17.6.1, the email addresses can only be configured via Comet Server, not by the Comet Backup app. A future version of Comet will allow users to change their own email addresses.

Quota 

Comet Backup supports Quota restrictions based on different types of data measurements.

All Protected Items Quota 

You can set a limit on the maximum size of all Protected Items in the user's account. When a backup job is performed, the total size of Protected Items is checked against this quota, and the backup job will be aborted if it would exceed quota. If possible, the quota limits are checked before starting the backup, to avoid inconvenient interruptions and wasted bandwidth.

Device Limit 

You can set a limit on the number of devices that may be registered into the user's account. If a user tries to log in to this account using a new device, the registration will fail with an error message.

Storage Vault quota 

For more information about Storage Vault quota, please see the "Storage Vault > Quota" section below.

Suspending Accounts 

An administrator is able to suspend user accounts in Comet Server.

In Comet 17.8.0, an administrator can suspend a user account by clicking the 'Actions' button and choosing the 'Suspend' option. You can unsuspend a suspended account in the same way.

A suspended user cannot log in to the Comet Backup application and cannot backup nor restore any data. A user is not able to un-suspend themselves.

Protected Items 

Overview tab 

In the "Description" field, enter a brief name describing what data is being backed up. Select which type of data is to be protected.

"Files and Folders" items 

No further documentation is available for this topic.

Filesystem snapshots 

On Windows, the filesystem snapshot feature (VSS) is required in order to back up files that are currently in-use. However, enabling this feature may cause unexpected issues when backing up network shares. Other platforms do not currently require the use of this feature.

Future versions of Comet Backup will simplify the behaviour surrounding filesystem snapshots.

Exclude filters 

You can exclude a range of files from the backup job. An exclusion filter can either be a "glob match" or a regular expression (regex).

Glob match 

Enter a path to exclude from the backup.

Some special characters and wildcards are allowed:

  • A star (*) skips zero or more characters within a filename
  • A double-star (/**/) skips any number of directory components
  • A question-mark (?) skips a single character within a filename
  • Square brackets denote a character class (e.g. [0-9]) within a directory or file name
Regular expression match 

This feature is available in Comet 17.6.13 and later.

Comet can exclude files based on a regular expression (regex). Any files matching the regular expression will be excluded from the backup job. The specific syntax flavour is that of the Go regexp library.

The regular expression is tested against the full disk path to the file. This enables filtering by path component, or (on Windows) drive letter.

By default, the regular expression is

  • case-insensitive. You can perform a case-sensitive match by adding an (?-i) expression
  • non-anchored. You can restrict your regex to the start- or end- of the file path by using the ^, $, \A and/or \z expressions.

Forwardslash (/) is not a special character and does not require escaping with \/.

System exclusions 

The Comet Backup system automatically excludes certain folders.

On Windows, Comet skips

  • The $RECYCLE.BIN and System Volume Information directories in any drive root
  • The C:\Recovery directory
  • The C:\pagefile.sys, C:\hiberfil.sys, and C:\swapfile.sys files (as of Comet 17.6.1)
  • Symbolic links on the C: volume that have both the hidden + system attributes
    • This is intended to work around an issue with application compatibility symbolic links used by the operating system.

On other platforms, Comet skips

  • Paths starting with /proc/

Rescan unchanged files 

This feature is available in Comet 17.3.0 and newer.

In a regular "Files and Folders" backup, Comet will skip over files that have the same file size and modification time as the last backup job. If these properties are the same, Comet will refer to previous chunks and not re-chunk the file. This dramatically improves performance.

If you are working with certain types of files that change content without updating their modification time attribute on the filesystem - for instance, applications that use direct disk I/O instead of filesystem functions; some database data files; or VeraCrypt container files - then the above is obviously unsatisfactory for ensuring backup integrity. In this case, you can enable the "Rescan unchanged files" feature to cause Comet to chunk every encountered file. This has some performance penalty but does ensure backup integrity in the presence of such files.

"Program Output" items 

The "Program Output" backup type backs up the stdout (Standard Output) stream of any command execution. This stream data is saved as a virtual file within the backup job. You can choose the virtual file name.

The data is streamed directly to the backup destination and never touches the local disk. This has the consequence that no progress bar or ETA can be calculated or displayed during backup jobs.

If the target application produces any content on stderr (Standard Error), it will be logged in the job report, and the final job status will not be less severe than "Warning".

If the target application exits with a non-zero error code, the error code will be logged in the job report, and the final job status will not be less severe than "Error".

"Microsoft Exchange Server" items 

Using this Protected Item type may incur a Booster charge.

This Protected Item type backs up Microsoft Exchange Server databases. The underlying technology is VSS and is compatible with Microsoft Exchange Server 2007 and later, including Exchange Server 2016 (the latest version at the time of writing).

The appropriate VSS writer must be installed.

As Exchange Server can only be installed on Server SKUs of Windows, this backup type is only applicable when running on Windows Server.

Some forms of Exchange Server backup will cause log truncation to occur on the Exchange Server. For more information, please see the Exchange Server documentation. If circular logging is enabled on the Exchange Server, the 'Incremental' and 'Differential' backup types have limited effect.

Exchange Server 2007 is only supported by Comet 17.9.7 or later.

"Microsoft Hyper-V" items 

Using this Protected Item type may incur a Booster charge.

This Protected Item type backs up Microsoft Hyper-V virtual machines. The underlying technology is VSS and is compatible with all versions of Hyper-V running on Windows Server, including Windows Server 2016 (the latest version at the time of writing).

This backup type is only applicable when running on Windows Server. Hyper-V on Windows Desktop is not supported by this Protected item type.

Comet integrates with the Hyper-V VSS writer to perform a Hyper-V backup snapshot, including support for in-VM quiescence on supported guest operating systems.

Backing up a Hyper-V virtual machine with Comet includes, but is not limited to:

  • its configuration file
  • all attached virtual drives
  • the contents of memory (if the machine was running)
  • the full tree of saved checkpoints

You can select individual virtual machines for backup, or choose "All virtual machines".

Consistency and guest additions 

When backing up a guest VM, it's important to get a consistent state of the VM. There are some different ways this happens. The following information applies to all products that perform Hyper-V backup:

If the guest OS has all necessary Hyper-V integration services installed, then the host can request for the guest VM to take a VSS snapshot. The snapshot is then exposed to Hyper-V on the host for Comet to back up. It shouldn't interrupt the guest OS.

If the host OS is running Server 2012 R2 or newer, but there are no integration services inside the guest OS, then Hyper-V will take a checkpoint of the VM; Comet will back up the checkpoint; and then the checkpoint will be removed. This kind of checkpoint does not interrupt the guest OS.

If the host OS is older than Server 2012 R2, and there are no integration services inside the guest OS, then the VM will be paused; Windows will take a VSS snapshot of Hyper-V's files in paused state; the VM will be resumed and Comet will back up from the VSS snapshot. It would cause a short interruption to the guest OS.

"Microsoft SQL Server" items 

Using this Protected Item type may incur a Booster charge.

This Protected Item type backs up a Microsoft SQL Server database. The underlying technology is VDI and is compatible with SQL Server 2005 and later, including SQL Server 2016 (the latest version at the time of writing).

No data is spooled to the local disk. As per the "Program Output" type, no progress bar or ETA appears during a Microsoft SQL Server backup.

Connection details 

Connection details should be supplied before selecting databases. Comet will only connect to SQL Server running on the local machine. You must enter the instance name, or leave the field blank to use the default instance.

Address 

The address is always localhost, but Comet does not use TCP addresses or TCP ports to connect to SQL Server instances. Comet uses "Shared Memory" to connect to SQL Server instances.

Comet's use of "Shared Memory" connection does improves performance for some operations, at the expense of only working on the local machine; but Comet's use of VDI requires it to run against the local machine anyway.

If you encounter issues connecting to your SQL Server, you must ensure that "Shared Memory protocol" is enabled in SQL Server Configuration Manager.

Authentication 

Comet allows you to connect to SQL Server using either Windows authentication (running as the local Administrator) or native SQL Server authentication.

  • If you are using Windows Authentication, the connection occurs as the local Administrator.
    • You can assign the local Administrator user to have sysadmin rights within SQL Server.
  • If you are using SQL Server authentication, you must enter a valid username and password to connect to SQL Server.

Impersonation is not currently available for Windows authentication. Future versions of Comet will support impersonation for Windows authentication.

Multiple instances 

Comet supports backing up multiple instances from SQL Server. You can select an instance for backup, by entering the instance name in the "Instance Name" field. Leave this field blank to use the default instance.

Comet Backup 17.6.3 automatically lists available instances for selection in the drop-down menu.

A future version of Comet will make the instance dropdown list available for remote administration in Comet Server.

Backup mode 

Three different backup techniques are available.

Full 

Comet Backup offers a high-quality deduplicated incremental backup system that is agnostic of data type. By default, Comet Server opts to make a full database export from SQL Server, and uses its own incremental system to optimise the stored/uploaded data. This is equivalent to the BACKUP WITH COPY_ONLY T-SQL statement.

Differential 

Alternatively, you can use SQL Server's own systems for differential backup. In this mode, you can regularly make "differential base" backups, and then a series of small "differential increment" backups, each containing the difference from the last base backup. These operations are equivalent to the BACKUP and BACKUP WITH DIFFERENTIAL T-SQL statements respectively. Comet will still deduplicate multiple base backups that are sent to the same Storage Vault.

To use SQL Server's own differential system, you must create multiple Protected Items (each with a different schedule) in order to capture both differential base and differential increment backups. This may at first seem like more work, but it simplifies the process of individually scheduling, reporting on, and managing retention policies for both base and differential backups.

Log 

You can opt to use SQL Server's own systems for log backup. In this mode, you must periodically take full image backups, and regularly take log backups. You have the choice of whether to apply log truncation. These operations are equivalent to the BACKUP LOG and BACKUP LOG WITH NO_TRUNCATE T-SQL statements respectively. Comet will still deduplicate all data that is sent to the same Storage Vault.

To use SQL Server's own log system, you must create multiple Protected Items (each with a different schedule) in order to capture both full and log backups.

This mode requires that the database Recovery Model is set to "Full" or "Bulk Logged" in SQL Server. For more information, please see https://msdn.microsoft.com/en-us/library/ms189275.aspx .

Recommendations 

In general, we would recommend using the default "Full" backup technique.

SQL Server's native differential/log systems may be used if you experience performance issues with the default mode, however, you must ensure that

  1. No other backup systems are resetting the last base backup;
  2. Whenever the differential/log backs up successfully, that the base has also recently backed up successfully;
  3. Base backups are performed regularly to minimise differential overhead; and
  4. Retention is carefully managed to ensure that recovery is possible

Alternative ways to back up Microsoft SQL Server 

You can use Comet's "Commands" feature to call osql/sqlcmd to run a T-SQL BACKUP statement against the database, and then back up the resulting spooled file with the "Files and Folders" type. This option requires more temporary disk space than the built-in system above.

You can use the "VSS-Aware Component" type to back up SQL Server using the VSS Writer. Compared to Comet's standard VDI approach, this option enables more detailed progress information, but offers more limited control over SQL Server features such as log truncation.

You can use the "Files and Folders" type to back up individual database files if the "Take filesystem snapshot" option is selected. However, the "Files and Folders" backup type does not invoke SQL Server's VSS writer, so this would (at best) produce a "crash-consistent" backup and is not recommended.

"MySQL" items 

This Protected Item type backs up a MySQL database. It is also compatible with MySQL-compatible servers such as MariaDB and Percona Server. It works at the logical (SQL) level.

No data is spooled to the local disk. As per the "Program Output" type, no progress bar or ETA appears during a MySQL backup.

Connection details 

Connection details should be supplied before selecting databases. Fill in the fields at the bottom of the dialog window.

Selecting databases 

Use the plus button on the right to open a database browser, allowing you to select individual databases for backup. Use the dropdown-plus button to add a custom property.

Custom mysqldump 

Comet Backup's MySQL support works at the logical (SQL) level using mysqldump.

The mysqldump binary is selected as follows:

  • If a custom path to mysqldump has been set, this binary is used.
  • Otherwise, if there is a version of mysqldump installed (e.g. you are backing up a MySQL server from the server itself), the local version of mysqldump will be used to ensure maximum compatibility.
  • Otherwise, if no copy of mysqldump can be found, the Windows version of Comet Backup bundles a recent mysqldump binary in compliance with its license.
  • If no suitable mysqldump binary is found, the MySQL backup job will fail. This failure can be detected via the backup job's status or its log entries.

"Windows Server System State" items 

Comet Backup integrates with Windows Server System State to support backing up System State .vhd files using the wbadmin technology. This feature is only available on certain versions of Windows Server with the "Server Backup Role" feature enabled.

A local path must be used for spooling temporary data. Spooled temporary data will be removed once the backup job completes. The selected path

  • must be a bare root drive, and
  • must support VSS, and
  • must have at minimum 10GB free space, and
  • must not reside on a "critical" volume (unless KB944350 has been applied).

For more information about Windows Server System State backups, please see

"Windows System Backup" items 

Comet Backup integrates with Windows System Backup to support backing up entire system volumes as .vhd files using the wbadmin technology.

Choose volumes to back up, and/or choose "all critical volumes".

A local path must be used for spooling temporary data. Spooled temporary data will be removed once the backup job completes. The selected path

  • must be a bare root drive, and
  • must not be included as one of the selected volumes.

"VSS-Aware Component" items 

Using this Protected Item type may incur a Booster charge.

About 

VSS is a technology for taking a consistent point-in-time snapshot of a disk volume. A VSS Writer is an extra software plugin that detects when this action is taking place and ensures that application-specific files are in a safe state on disk. Comet's "VSS-Aware Component" feature allows you to invoke a single VSS Writer, or a sub-component of a single VSS Writer, and back up only the files that it was protecting.

For instance, you can use this Protected Item type as an alternative backup solution for Microsoft Exchange Server, Microsoft Hyper-V, Microsoft SQL Server, and other products.

This is also an important third-party integration point for application vendors. If your third-party application includes a VSS Writer, you can use this Protected Item type to back it up using Comet.

Selecting components 

In Comet Backup, click the Edit button (pencil icon) to browse the available VSS Writers installed on your device.

You can select the top-most checkbox to include all components within the VSS Writer, or you can select individual components within the VSS Writer. For instance, the Microsoft SQL Server VSS Writer allows you to select individual databases for backup.

The VSS Writer itself may mark some components as non-selectable. This is shown in Comet as a grey subcomponent without a checkbox.

VSS Mode 

You can perform the operation in "VSS Full", "VSS Copy", "VSS Incremental", or "VSS Differential" modes. If a specific VSS Writer does not support the selected backup mode, it will perform the backup in "Full" mode.

The actual behaviour of these modes is specific to each VSS Writer. For more information, consult the documentation for your VSS Writer.

Schedules 

No further documentation is available for this topic.

Commands 

The Commands feature on a Protected Item works the same way as for Commands on a Storage Vault or on a Schedule. For more information about the Commands feature, please see details under the "Overview and Concepts" section.

Retention 

On the Retention tab, you can configure a retention policy to apply when backing up this Protected Item to a specific Storage Vault. If no policy is configured for a specific Storage Vault, the default retention policy for the Storage Vault will apply. For more information about retention, see the "Retention" section below.

Retention 

"Retention" is the concept of classifying backed-up data, to determine what data should be kept, and what data can be safely removed in order to free up disk space. For instance, you may choose to keep the last 30 days' of backed-up data, or all data from the last 100 backup jobs; but any data older than this is unlikely to be useful and can be safely removed.

Retention Pass 

After each backup job, a "retention pass" runs for the Storage Vault. You can also run a retention pass for a Storage Vault on demand, by right-clicking the Storage Vault within the Comet Backup application.

During a retention pass, Comet Backup looks at each backed-up job within the Storage Vault and determines whether it meets the retention policy. If the retention policy states that the backed-up job can be safely removed, the backed-up job is removed from the Storage Vault. Once all backed-up jobs are checked against the retention policy, any data chunks that are no longer referenced by a backed-up job can then be pruned to save disk space.

Preferences 

Comet allows you to configure retention for a Storage Vault, as well as for a Protected Item / Storage Vault pair.

The retention rule for the pair will be used in preference to the retention rule for the Storage Vault. The retention rule for the Storage Vault is therefore only applied when

  • there is no overridden retention rule for the Protected Item / Storage Vault pair; or
  • the Protected Item is unknown, deleted, or belongs to a different Comet user account

Retention policies 

In Comet 17.6.1 there are two categories of retention policy:

  • A policy that keeps all data forever, and
  • A policy that keeps data as long as it falls within any of a set of configurable ranges. You can combine multiple ranges to create a more complex policy.

Retention ranges 

A retention range is a time period or job count during which a backup job should be kept.

The following ranges are available:

"Last [...] backups" - Specify a number of backups to keep. If the backup job was within the last X backups, then the backup job will be kept.

"All backups in the last [...] - Specify a number of days, weeks, and/or months. If the backup job occurred recently within the specified range, then the backup job will be kept.

"All backups newer than a specific date - Specify a specific date. If the backup job occurred after that specific date, then the backup job will be kept.

Future versions of Comet may make additional Retention Range options available.

Storage Vaults 

General tab 

On this tab, you can give a name to the Storage Vault. You can use any name; if you have multiple Storage Vaults within an account, we would recommend using a name that identifies the content and/or purpose of the Storage Vault.

On this tab, you can also configure a retention policy for the Storage Vault. For more information about configuring retention, please see the "Retention" section below.

Quota (Storage Vault) 

On this tab, an administrator using Comet Server can configure a quota limit, restricting the total amount of data stored within this Storage Vault.

You can set this property on a per-Storage Vault basis. For example, you could use this feature to limit the amount of data stored on an expensive network storage account, but still allow any amount of data to be stored on a local hard drive.

When a backup job is performed, the total size of the Storage Vault is measured and checked against this quota limit. As the job proceeds, the amount of uploaded data is compared against the remaining available size, and the backup job will be aborted once reaching this limit.

After a quota has been exceeded 

A backup job that is abandoned for reaching its Storage Vault quota does not remove the chunks that were uploaded to the Storage Vault. Future backup jobs will almost certainly fail immediately. In this situation, you have the choice between

  1. Raising the Storage Vault quota and retrying the backup. This will cause any existing chunks in the vault to be re-used, accelerating the backup quickly up to the point where it was interrupted; or
  2. Using the "Apply retention rules now" feature to clear unused chunks from the Storage Vault. This will reduce the data size within the Storage Vault and allow future backups to proceed.

Neither action is taken automatically - you should choose one action to take depending on the situation.

Storage tab 

On this tab, you can configure the data storage location for this Storage Vault. A number of types are available, including local disk storage, network accounts, and cloud storage providers. For more information about data storage locations, please see the "Storage Configuration" document.

Commands 

The Commands feature on a Protected Item works the same way as for Commands on a Storage Vault or on a Schedule. For more information about the Commands feature, please see details under the "Overview and Concepts" section.

Encryption 

No further documentation is available for this topic.

Devices 

No further documentation is available for this topic.

Policies 

An administrator can configure additional policy restrictions via the Comet Server web interface.

As of Comet 17.8.0, the available policy restrictions are:

  • Prevent creating new Storage Vaults (via Request)
  • Prevent creating new Storage Vaults (via Custom)
  • Prevent editing existing Storage Vaults
  • Prevent deleting Storage Vaults
  • Restrict available Storage Vault types
  • Prevent creating new Protected Items
  • Prevent editing Protected Items
  • Prevent deleting Protected Items
  • Restrict available Protected Item types