Disk-to-Disk-to-Tape Backup on the Cheap

One alternative is to back up data on disk, which is inherently faster than tape. Some users are taking an extra step by adding tape to the mix, creating disk-to-disk-to-tape (D2D2T) backup systems.

Commercial D2D2T solutions are cool. They use iSCSI and Fibre Channel connectivity to provide high-bandwidth SAN (storage area network) links. These links let multiple servers simultaneously push big byte loads of data from production disks to D2D2T disk and tape farms. The idea is to first quickly provide disk-based protection for an organization's crown jewels, then to archive backups to tape at a more leisurely pace.

But commercial D2D2T systems from vendors including Breece-Hill, Overland Storage, and Certance are also costly. The cost for a high-end D2D2T system with 2 GB of disk and tape is around $20,000. (If you're interested in such solutions, see my review of the Certance CP 3100 in the July 2 issue of VARBusiness.) To give you a sense of how these boxes look, here's a photo of Breece-Hill's iStoRA 4000, a sleek black box that will set you back a cool $19,400:

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But what if you -- and your clients -- don't have nearly $20,000 burning a hole in your pockets? In that case, I'm here to show you how to build a low-cost D2D2T solution. While this low-cost system won't have every bell and whistle you'd find on a commercial product, it will help your clients deal quite effectively with data inflation -- and without breaking the bank.

This Recipe assumes a Windows 2000 or 2003 server environment. The system we're going to create is designed to run on just one server and to back up only local files. Later, I will explain how to use the system to back up other servers and workstations on the network. I'll also briefly mention how this recipe could be adapted to other, non-Windows operating systems. But first, let's look at the minimum set of ingredients you'll need to get started.

Minimum Ingredients

The diagram below shows how your simple D2D2T solution will be configured for backing up local files:

The Server

For my D2D2T server, I prefer to use a non-file server that isn't heavily loaded with applications. In some situations where backup loads may be heavy during business hours, I've actually installed a new server. In other situations where loads are likely to be light, I've used application and file servers -- even domain controllers.

The Backup Software

My favorite backup software is Veritas Backup Exec for Windows Servers. It makes both backup to disk and finding files for recovery very easy and simple. But any software that can back up to both disk and tape is fine. These include Computer Associates' Brightstor and the backup program that comes with Microsoft's Windows 2000 and 2003 server products.

Do you need to backup databases such as SQL Server, Oracle, or Exchange while they are online? If so, you'll also need to ensure that your backup software includes agents for these databases.

Once you have your software installed, it's time to implement disk-to-disk (D2D) and disk-to-tape (D2T). You simply set up jobs using your backup software. For D2D backups, you need to specify a place on disk -- a file -- where each backup will be stored. Because an entire backup goes into one file, you can't just go in and find a file with Windows Explorer. Instead, as with tape backups, you'll need to access and recover files with your backup program.

By judiciously scheduling jobs and setting expiration dates for backups to disk, you can set retention schedules for backups to disk, just as you do for backups to tape. Schedules also assure that files move to tape in a timely manner. If you leave backups on disk for longer periods of time, you have a redundant backup on tape. If you implement short retention times for disk and longer times for tape, your tape backup quickly becomes an archive.

The screen shot below shows a series of regular backups to disk as set on Veritas Backup Exec:

The Disk Drive

Fancy D2D2T devices incorporate multiple disk drives, often the new Serial ATA (SATA) disks. Most D2D2T units support at least RAID 5, providing better protection for disk-based backups. If you have access to RAID for backups to disk, that's great. If you don't, you can still take advantage of those great USB 2 and Firewire external drives from vendors such as Maxtor, Seagate, and Western Digital. Below is a photo of Maxtor's 250-GB external drive, which includes both USB2 and Firewire interfaces:

While one such drive is okay, multiple drives will let you add both capacity and redundancy. Think about it: Four 250-GB external drives give you 1TB (a trillion bytes!) of storage for only $800 to $1,000 at today's prices. You can either use all that storage for backups or you can copy backups from one disk to another for redundancy. You can use your backup software to make the copies. Backup Exec makes this very easy. Or you can use a product like ViceVersa from TGRMN Software to initiate automatic copies from one disk to another whenever anything changes on the first disk.

I strongly urge you to use redundant drives. Large-capacity external drives run very hot. I have a business partner who, over the past two years, has lost three out of 10 drives due to failure from overheating. Of course, it doesn't hurt to keep your drives cool, as well!

The Tape Drive

High-end D2D2T systems use tape auto-loaders and high-capacity tapes -- 200 GB and more -- such as those manufactured in accord with the LTO 2 (linear tape open) standard. These devices are expensive. If you already have a DAT drive in your server, you can use it. But you'll probably find yourself changing tapes more than you want to, just to accommodate the massive amounts of data you're backing up to disk. The good news is that you are backing up backups, not live data. So if you don't get around to changing a tape for a little while, the world won't come to an end.

There's even better news. Take a look at Iomega's new <>folder_id=16006169&ASSORTMENT<>ast_id=63191&bmUID=1087585354632">REV removable disk drive. It has a native capacity of 35 GB and costs about $350, making it a cost-effective replacement for a higher-capacity tape drive. The REV's removable cartridges cost less than $50 in quantity and are sure to come down in price with time. So with this unit, you can have near-DLT tape capacity at a much lower hardware price and near-comparable media prices. Here's how the REV looks:

Even better, the REV drives are faster than tape drives. You can even back up in native Windows file format by using a program such as ViceVersa. So what if you wind up with a D2D2D system? As long as you can remove your backups and take them off-site, who cares?

Backing Up Other Servers, Other OSes

What if you want to back up other servers or even workstations on your network? Or, what if you want to back up non-Windows operating systems? In these cases, you have two possible solutions: drive mapping and iSCSI.

On your D2D2T server, you can simply map a drive to another Windows server or workstation. Then you can back up files using the drive mapping. Additionally, you can map a drive to a non-Windows computer -- Linux, for example -- and backup files through that mapping.

The problem with drive mapping is that you often can't effectively back up entire disk drives, especially OS drives. With drive mapping, all of the backup work is done by your D2D2T server.

This is where iSCSI comes in. Using software on your D2D2T server, you turn the server into what is called an "iSCSI Target." This sets up the server so that when other computers run so-called iSCSI Initiator software, they see specific disk drives on your D2D2T server, as if the disks were locally attached drives. (All of this works over standard Ethernet TCP/IP networks.) Using these virtual local drives, iSCSI Initiator servers and workstations push jobs to the D2D2T server using their own copies of the backup software. With iSCSI, you essentially create a backup storage attached network (SAN).

iSCSI Initiator software for Windows is free. You can download it from this Microsoft Download Center. iSCSI Initiator software is also available for Linux and NetWare; check with your Linux vendor or Novell for more information. Also, iSCSI Target software for Windows is available for $250 per server from String Bean Software.

With iSCSI, you come closer to the power of commercial D2D2T products. For example, multiple servers or workstations can simultaneously push backups to your D2D2T server. The initiators, instead of your D2D2T server, do much of the backup work.

If you want to get into multi-server push backups, you'll want to seriously consider building a Gigabit Ethernet backbone. Gigabit Ethernet prices are low, and building such a backbone is easy.

Finally, what if you want to build your D2D2T server on another OS platform? Pretty much everything is the same, except maybe for the backup software and, should you chose to use it, the iSCSI Target and Initiator software you need to use.

Good luck!

BARRY GERBER is a Los Angeles-based electronic communications, networking, and storage consultant and author. He is the author of "Mastering Microsoft Exchange Server 2003" (Sybex, 2003) and co-author of "Microsoft Exchange Server 2003 24seven" (Sybex, 2004). Barry has no commercial connections with any of the products or vendors mentioned in this Recipe.

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