Highly Reliable Systems: Removable Disk Backup & Recovery


Using Removable Drives for Softwareless Backup

By Tom Hoops

Highly Reliable System’s 2 bay High-Rely, RAIDFrame, MPac, and FirstRAID removable drives allow users unique backup possibilities.  This paper discusses softwareless and automatically redundant backup strategies.

The 2 bay High-Rely, RaidFrame, and FirstRAID all have Automatic Mirror Technology (AMT).  AMT devices don’t require special RAID drivers or controllers on the host because the board is integrated into the external unit.  This custom RAID 1 board allows them to mimic a standalone USB3 or SATA hard drive.  Unlike typical mirror systems, which are only intended to offer you data protection with occasional drive failure, the 2 Bay AMTs also provide daily backup functionality.  Remirroring happens with each drive swap.  The FirstRAID and 2 Bay RAIDFrame have the same functionality but add the redundancy of RAID5 arrays.

In a recent case study at leading video producer the client connected a FirstRAID AMT to their Windows 2003 server and shared the main RAID5 array to their users.   All of the company’s daily work is done directly on the external RAID volume.   They could have installed high RPM drives and a RAID controller inside the server, but the cost and available space made that approach unworkable.  Internal storage does provide fast write performance, but the client didn’t need multi-user simultaneous access to databases and there are fewer than 15 users.  The FirstRAID is no performance slouch and provided more storage than would fit in the rack mount server.  Plus it doubles as both primary storage and backup in one unit.  With AMT, once the data is synced  information which is changed or added during the workday is replicated to the removable drive.  Essentially the system does the equivalent of “continuous data protection – CDP” without the need of any software or configuration.

The video production company also purchased 5 extra High-Rely classic removable drives.  Each evening they rotate in a new one and transport the old one off site. The remirroring process begins immediately at a data rate of approximately 300  to 400 Gigabytes/Hr.  When the system has created a copy of the data to the removable drive (usually by next day), an LED signals the user the copies are in sync.   No backup software is required in this type of installation. Because the 2 drive AMT units stay connected and online without notification or operational changes to the host when a drive is swapped, the host can treat the unit as it would an internal drive.  This example is what we call “softwareless” backup.  The 2 bay High-Rely classic AMT offers the same capability at an even lower price point using 2 individual SATA drives. Optional monitoring software can also be used to send email alerts on critical events (mirror complete etc.) or remotely check the activity/error log, note syncing progress or change configuration.

Care should be taken to train the operator not to swap drives before mirroring is finished to avoid data loss or partial mirrors.  While only a small portion of data is potentially at risk if the drive is removed while the system is actively writing, it should be avoided. It is best to swap the drives at a time which there should not be any activity or after closing applications that would be writing.

Another case study is a web server running Ubuntu 10.1 Every night, the machine runs a script which simply mounts a 2 Bay High-Rely Classic AMT as a single drive, compresses the contents of the system and stores them on the what looks to it like a single external drive. In the morning, one of the Tandem’s (2 bay AMT) media is swapped out for off site backup.  While this case does use “software” for backup in the form of the script it runs, it would have been just as easy to configure the webserver to store and work on it’s data and contents on the 2 bay device in real time. The same process of swapping drives out in the morning would work.

Recovering from a failure is as simple as replacing the master with a previous backup.  While you can manually switch mirroring off on the AMT systems, the danger of beginning to remirror when inserting an older archive should always be avoided.  If older, archived drives are needed for the restore, another High Rely device, such as the inexpensive High Rely SATA/USB3 one bay can be attached to simplify things.

Backup software certainly has its place and AMT may not render it obsolete. But, after analyzing your needs and use you may determine that by using our hardware mirroring and you can go without the software.

Tom Hoops

About Tom Hoops

CTO/VP Engineering, Highly Reliable Systems, Inc. View all posts by Tom Hoops →


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