Bare-Metal Recovery : Solaris Bare-Metal Recovery - Using Flash Archive

2/1/2015 8:42:25 PM

The following section gives you an overview of how flash archive can be used to perform bare-metal recoveries. It also provides a list of setup questions to consider when setting up flash archive.

Backup and Recovery Overview

The following is a quick overview of the basic process of using flash archive to back up and restore the Solaris operating system.

Perform the backup

  1. Create a flash archive image on disk (such as an NFS mount) or tape using the flar create command.

  2. If you create the flash archive on disk, you can also create a tape image from the disk image using dd.

Perform the restore

  1. If you plan to restore from tape, place the flash archive tape in a tape drive local to the system being restored.

  2. Boot from the system to be restored either from a Solaris Installation CD or via the network.

  3. Continue the normal boot process until you reach the Specify Media panel.

  4. Select either Network File System or Local Tape, based on where your flash archive image is located.

  5. Select the image to restore from, and follow the prompts to complete the restore.


If you set up a noninteractive restore, steps 3–5 are automatically performed using your configuration files.

Initial Considerations

Before using flash archive, there are many things to consider. This section will help you decide which methods of backup and recovery are best for you, based on your requirements.

System requirements

Flash archive has the following minimum system requirements:

  • Solaris 8 (HW 04/01) or later

  • Sufficient disk space to store the flash image or a supported tape drive connected either locally or remotely to the system.


Please test your flash archive recoveries before you really need them. You don’t want to find out that your new system isn’t supported or that your method of recovery won’t work.

When restoring an existing image, your Sun system must have a CD/DVD drive and a bootable CD/DVD of the Solaris operating system, or access to a Solaris network boot server that supports flash archive installations. The version of Solaris used should be the same or greater than the version of Solaris used on the source system. For example, when recovering a Solaris 9 (HW 09/05) server, you should boot from a Solaris 9 (HW 09/05) or later CD/DVD. (The urgency of this requirement varies depending on the OS version, but I strongly recommend that you use the same or later version CD to avoid potential problems.)

If you plan to perform restores to dissimilar hardware, the system being backed up should include the entire Solaris distribution plus OEM support (SUNWCXALL). If you are restoring a system with a limited Solaris distribution to a system with different peripherals or of a different architecture (for example, Sbus versus PCI bus), required drivers may be missing and the recovery can fail. If you plan to perform restores on the same hardware, this is not a requirement.

Frequency of backup

Your individual requirements determine how frequently you create flash archive images. If you’re using flash archive images only for bare-metal recovery purposes, you definitely need to create a new image every time you make a change to the server that you want included when performing a bare-metal recovery. Most users of flash archive, though, automate the creation of fresh flash archive images on a regular basis, which makes sure that your system images are always up to date.

Back up to disk or tape?

Flash archive images can be written directly to disk or tape, and you’ll need to make a choice as to which option works for you. How you plan to use the images plays a large part in determining whether to use tape or disk. For example, if flash archive images are created solely for the purpose of off-site bare-metal recovery, you may conclude that a tape-only environment is right for you.

Most environments use a combination of tape and disk by storing a flash archive image on disk, and then copying to tape periodically. This lets you send a copy of the image off-site for disaster recovery purposes and retain a copy on-site to restore a server locally. Companies may also choose to implement a flash image server. In this case, flash images are stored on and restored from a central server. Many system administrators also use their existing Jumpstart boot servers to store their flash images (Jumpstart is a Sun tool used to simplify Solaris installation). This provides a network-based boot and an image to recover from all in the same place. In either case, the server may also have one or more tape drives attached to provide an easy way to create portable copies of the image for storage off-site.

If you are considering using disk, keep in mind that sufficient disk space is required to store the flash archive images. Depending on the options selected during the image creation process, a flash archive is typically between 75 and 100 percent of the size of the filesystems included in the archive.

Restore from tape or disk?

A flash archive image can be used locally to restore the Solaris operating system on a server that has failed. In this scenario, either tape or an NFS mount provides an excellent source from which to recover. If hardware and network resources permit, it is recommended that images be stored on disk and restored over an NFS mount. Generally, this method requires less locally attached hardware (useful when recovering multiple servers) and is usually faster than tape.

A flash archive image can also be used to restore a system in an off-site location, such as in the case of a disaster recovery. In this scenario, a company may decide that restoring critical servers directly from tape is its best option. Others, depending on several factors (number of servers to restore, hardware availability, etc.), may decide to restore all flash images to disk and perform the actual flash recoveries from an NFS mount.

Finally, another option worth mentioning is the use of cloning in conjunction with flash images to build new servers. This option allows users to deploy a standard, hardware-independent build to servers much quicker than if Solaris had to be installed separately on each system.

Interactive or noninteractive restore?

When deciding how to set up flash archive, you first have to decide whether you want to be able to perform an interactive or noninteractive restore. An interactive restore requires almost no initial setup but more input is needed during the restore process. It may also entail more significant post-recovery efforts. A noninteractive restore method requires more setup work but calls for little to no input during the restore process (when time is typically critical).

Either method is considered acceptable. However, since time is usually most critical when a server is down, most system administrators find the time spent creating the files and scripts up front for the noninteractive restore method to be a worthwhile investment.

Other environmental constraints

Many organizations use DMZs and other network tools to restrict access from certain systems to the production network. If this applies to your company, consider how it will impact your implementation of flash archive.

It is recommended that the flash archive infrastructure in a DMZ should mirror what is available in production. Examples of required infrastructure include tape drives, NFS servers, and backup servers. If resources are not available to mirror the production infrastructure, be sure to have a tested, reliable process in place to back up and restore the servers in the DMZ.

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