TCO analysis: where D2D fits--part 1.

There are thousands of storage systems that are being used for disk-to-disk (D2D) backup and it appears that nearly every customer is considering implementing a solution within the next 18 months. Backing up to disk is one of those things that just makes sense. The price of hard drives is decreasing while capacities increase; data growth is off the charts; backup windows are shrinking; reliable recovery of data is requisite; and D2D technology is advancing.

The Enterprise Strategy Group recently completed a report, The Evolution of Enterprise Data Protection, which surveyed over 220 IT managers. Based on this research, the majority of these users are using or will be deploying D2D solutions of some variation. The benefits are clear:

* Increased backup performance

* Decreased time to recover

* Ensured data integrity and recoverability

* Media management issues

Some of the reasons that customers were interested in deploying D2D solutions:

* "One problem we have is that we can't recycle backup-tapes fast enough. This has really affected our ability to backup and restore desktops. Our backup application backs up all daily changes across thousands of desktops so tapes get filled up pretty quickly. It sometimes takes us three days to restore a desktop because the user's data is scattered across 40 different backup tapes!"

* "With tape-based systems, the human overhead of managing tapes is much more pronounced than with disk-based products."

* "We really only want to use tape for disaster recovery purposes. We'll address data retention with cheaper, more readily accessible disk technologies."

* "A big problem we have is that we have no way to know whether or not a backup tape is good until we try to recover."

The question is not whether to implement a D2D solution but what options are available, and which will solve the problems to meet your needs.

Backup to Disk (B2D)

On the surface, backup to disk is very straightforward. Most major backup software applications allow users to backup to a disk target. Customers did not back up to disk in the past due to the high cost of disk storage. Today low-cost, high-capacity ATA drives makes backing up to disk economically practical. But backing up to disk is not as simple as it would seem. There are issues that IT managers should be aware of.

The file systems on the media server qualified by the backup vendors typically have a 2-TB limitation. This will impact scalability, management and performance. You can get around this by installing a third-party file system but this will add cost and complexity. Using a host-based file system may expose you to viruses, file corruption, and accidental or malicious file deletion.

The storage array used for the backup must be configured and managed and comes with all of the same technical challenges as any other SAN-attached system. Imagine managing 50TB of backup data. Based on the 2TB file system described, this would mean that the storage administrator would have to support 25 file systems. And if you configure a LUN per file system, that equates to the management of 25 LUNs. Backup polices will more than likely need to be reconfigured to backup to disk.

Having said this, there are a number of users that are doing exactly what is described above. In the ESG report, a large number of customers are using ATA drives in their storage arrays and are performing backup to disk. Right now, this solution is good enough for their purposes. But as the demand and storage capacity grows, IT managers should look at special built D2D solutions, including backup to disk (B2D) appliances and Virtual Tape Libraries.

NetApp and Data Domain are two vendors that provide B2D products that resolve some of the issues described above. NetApp supports up to 16TB in a file system; Data Domain supports 1.5TB (most customers want to keep data sets small to maintain decent recovery performance) and provide powerful compression capabilities that allow customers to effectively store more data with less actual used storage capacity. ESG Lab tested Data Domain and found that they can easily achieve 20:1 compression.

Both NetApp and Data Domain have developed products that have their own file system. This eliminates the issue of file corruptions, viruses and file deletions. Data Domain claims that their file system was designed to recover from major disasters allowing users to rebuild data with just the drives.

Both products are NAS systems, which are usually easier to install and manage than a SAN storage array. Backup polices will still need to be modified to work with these solutions; however, customers that have done this say that the changes are minimal.

Virtual Tape

Virtual Tape is not a new concept and has been widely used in IBM Mainframe environments for years. ESG research has found that approximately 60% of all IBM Mainframe data is protected by virtual tape. Virtual Tape solutions now support other operating systems including Windows, Unix and Linux.

Virtual Tape Library (VTL) solutions are storage subsystems that emulate a tape library and use RAID-protected hard drives to store the data. Typically the VTL solution has its own file system, emulates multiple tape libraries, and provides additional performance boosts through load balancing and large block sizes.

Advantages of Virtual Tape Solutions

VTL solutions support their own file system that provides larger storage capacity and reliability. The amount of capacity ranges depending on the product. Products from ADIC, Quantum and Sepaton support up to 40, 64 and 200TB respectively.

These systems are completely transparent since they emulate the tape library and therefore policies do not need to be re-written. Customers that have deployed VTL solutions are using them in their production environments out of the box in a few short hours.

VTL solutions should provide a significant improvement in backup performance since these solutions typically provide load balancing and support large block sizes. Restore from VTL should be much faster than tape.

As mentioned above, since VTL solutions have their own file system the reliability and recoverability should be rock solid. There are a handful of VTL providers with a mixture of startups and established companies providing products in this space (see Table).

The End of Tape?

Not according to our research. ESG research found that most users will continue to use tape to archive data offsite for at least the next two years. Customers will continue to use tape because they have already invested time and money into their solutions, tape is a removable media, and tape cartridges are still less expensive than hard disk drives. For the short term, D2D backup is being used in conjunction with tape and not as a complete replacement. Customers typically keep between two and five months of backups on disk for rapid and reliable recovery, which is more than sufficient since ESG research found that 56% of all recovered data is less than 2 days old and 79% is less than 7 days old.

Conclusion

Over 50% of customers that ESG surveyed believe that all of their data will be backed up to disk at some point in its lifecycle. Additionally, nearly half of the customers surveyed are already backing up some of their data to disk today. Customers will see more solutions being offered in 2004 by new and established vendors, which will help with the adoption rate of D2D solutions. EMC entering the market, on some level, legitimizes it and creates opportunity for all D2D providers.

Customers that have not deployed a D2D solution are primarily concerned with cost and are dealing with other higher priorities. Early adopters have deployed D2D to improve backup performance; rapidly restore data; ensure data integrity and recoverability; and manage their people resources more efficiently. The IT community has started to embrace D2D and its use will become a more strategic and requisite part of an overall data protection strategy and life cycle management process.

  Vendor     Product   Integrated or  Emulated Tape Libraries
                           SW

ADIC        Pathlight   Integrated    ADIC Scalar series

Alacritus    Securitus      SW        Multiple

Copan        VTL         Appliance    ADIC, HP, IBM, STK

Diligent     VTF Open       SW        Multiple

EMC DL       VTL         Appliance    ADIC, HP, IBM, STK

FalconStor   VTL         Appliance    ADIC, HP, IBM, STK

Maxxan       VTL         Appliance    ADIC, HP, IBM, STK

Overland     REO        Integrated    Overland

Quantum      DX100      Integrated    Quantum only

Sepaton      S2100      Integrated    Multiple

www.esglab.com

Tony Asaro is a senior analyst for the Enterprise Storage Group (Milford, MA)