Just look at some recent litigation that has come about as a result of failed restores from tape. The cost for restoring e-mail from tapes in the 2005 Zubulake v. UBS Warburg employment discrimination case came to $29 million, the cost of the verdict due to some key messages being missing. Similarly, Morgan Stanley lost a $1.45 billion judgment after it overwrote some archived e-mails and had trouble processing backup tapes containing others.
Still, tape storage has been around for half a century and remains the backbone of many recovery strategies. But it is far from ideal. Creating full tape backups, doing a full restoration of the system and then a full restoration of the data is slow and painful.
Frequently files can't be recovered at all.
Tape is increasingly being exposed as a substandard medium for backups, says Simon Robinson, research director, storage, for consulting firm The 451 Group of San Francisco. Users like it because it's cheap; but it's inherently unreliable and performs poorly. Tape still has its place as a longer term archive, but is being superseded by disk.
Tape is far from dead, of course, and in terms of price it is hard to beat. According to The 451 Group, tape storage runs about 12 cents per gigabyte compared to 50 cents for secondary disk storage and $2.50 for primary disks. But with the price of disk getting ever closer to tape, it is now considered economically viable for routine backup. Tape, on the other hand, is the preferred venue for long-term, off-site archiving.
Certainly, the numbers support the trend away from tape. Consulting firm IDC of Framingham, Mass. says the worldwide market for disk-based data protection hardware and software hit around $8 billion in 2006. By 2010, analysts predict t will expand to $50 billion.
Many IT organizations use disk as the backup target to shrink their backup window or improve access times for restore, says Lauren Whitehouse, an analyst at the Enterprise Strategy Group in Milford, Mass. Some organizations leverage virtual tape library (VTL) solutions, which emulate tape devices to the backup application, and others are implementing the disk backup options of their backup solution.
Disk can be used for data protection via such technologies as RAID, replication, mirroring and snapshots. Snapshots, for instance, provide more-current data for restoration than nightly backups, and are easier to restore than tape.
We recommend using disk-to-disk backup using block level snap-vaulting for operational backup, says Joe Shields, director of systems engineering and operations at Lightedge Solutions Inc., a managed network, voice services and hosting company in Des Moines, Iowa. This provides a short recovery time objective and is cost effective.
W. Curtis Preston, vice president of data protection services at GlassHouse Technologies Inc., a storage consultancy and services firm in Framingham, Mass, brings up another problem there is often a mismatch between network and tape speed.
You are not always able to supply the tape drive with enough data so it stops and starts when trying keep up with the slow incoming data rate, says Preston. This can even cause the backup to fail.
Better match ups in data rates can be achieved by using disks as an intermediary step in tape backup (disk-to-disk-to-tape backups). York University in Toronto, for example, uses disks to speed up the backups on its databases.
We will be able to do backups much faster from the server standpoint and then cycle it to tape during the day, says Ramon Kagan, York's manager of Unix Services. This will save a lot of time.
Disk, Tape or Combo?
The question of which technology to utilize, though, is far from an easy one. Some organizations might do fine sticking with tape. Others might be better advised to go whole hog on disk. But most experts say technology is the wrong place to start looking.
The problem that most organizations have is they are not asking the right question, says Cougias. We back up data to protect the continuity of our systems and our data.
The place to begin, he says, is an assessment of what data and systems need to be protected and what is the cost if they go down. The ideal, of course, is fully redundant systems so service is never lost. Next best is to quickly restore data when one a problem occurs. However, not all data and systems require the same level of protection.This article was first published on EnterpriseITPlanet.com.