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INTRODUCTION Backup is one of the thornier issues facing the network administrator, but it is also one of those most likely to find itself at the bottom of the “to do” pile. Let’s face it - backup is not particularly glamorous at the side of investigating Gigabit Ethernet or load balancing technologies. Surely it is more important to keep our network running smoothly and at peak performance? The lure of the user’s accolade is also very strong. Improve the response time to the workstation and you are an instant hero. Improve the chances of recovering a file after a disaster, and all you are likely to get is “Why is the response time so poor?” After all, a disaster is something which only happens to someone else .... isn’t it? So why spend lots of money on a boring old backup system? Cheap tape devices can be picked up from most mail order PC warehouses these days, and the operating system comes with a backup utility for free, doesn’t it? There is far more to backup than simply stringing together a PC, a tape drive and a piece of software, however. Although low-end tape devices have become commodity items, it is worth putting some thought into the requirements of your particular situation before spending money on something which may not satisfy your needs in the long term. Backup software too has become extremely sophisticated and feature rich, and the utilities included “free” with your operating system offer little more than a “taster” of what you can expect from a full-blown package. If you truly value your data, the backup system you choose should offer the following features : - Backup must be done within a narrow, predictable, inflexible window. The backup window cannot vary with the amount of file system activity, and is often non-existent in today’s 24x7 networks.
- Backup must be done at maximum speed.
- Backup must be completed even in the event of a cartridge or tape drive failure.
- Restore must be accomplished at maximum speed.
- Restore must be accomplished even if a cartridge is destroyed, mislabelled or missing from the original backup set.
- Restore must allow individual file or mailbox restoration.
- Simple backup management paradigm.
For many organisations, the backup application serves as a cornerstone to an expanding data management strategy that involves archival and retrieval. It used to be that backup and secondary storage strategies were driven by the relatively high cost of disk - now they are driven by the sheer amount of data and its thousands of distribution points across multi-server networks. That is why we have entitled this document “Data Storage Management”. This is not just a fancy term for “backup”, since in order to implement a really effective backup policy you need to be on top of your data management. Consider what would happen, for example, if you were to attempt to backup your 320GB server-based RAID array to a single DAT drive. Even with the best compression technology in the world, you are not going to fit this amount of data on a single tape. The result is a partially complete backup job, with the console requesting another tape when you return to work in the morning. What do you do then? Put the second tape in and keep your users off the system for the rest of the morning until the job is complete? Or abort the job and run the risk of operating with unprotected data? Hopefully we are about to dispel many of the myths and explain some of the jargon surrounding the storage management industry. The first section of this document looks at the backup issues facing most administrators today - mainly centred around too much data and too little time. What features should you look for in a backup package - file by file or image backup; push agents; automated tape rotation; directory services support; open file support? And how can you best design your network to take advantage of the limited backup window you have available? We also examine the various standards applicable to the backup industry, and look at how you might go about implementing a comprehensive backup regime. The second section covers some of the more advanced features that can be found in today’s high-end backup solutions. Anti-virus scanning, centralised management, fault tolerance, and for those of you already experiencing the trauma of a disk subsystem which is constantly creaking at the seams, we look at what data migration and Storage Area Networking (SAN) can offer you. Although these features are often perceived as too expensive for anything but the largest corporations, this is simply not the case with many of today’s systems. Finally, we explore the world of backup devices, sorting through the bewildering array of offerings and attempting to offer some guidance as to which might be the most suitable for your particular application. The choices out there are bewildering and there are many pitfalls to trap the unwary on the way to implementing a comprehensive data storage management strategy. Disk grooming, data migration, SAN, NAS, tape arrays, autoloaders - these are all technologies which can help to keep your data under control, and each of them will be examined as part of this document. The importance of data as an asset in modern business Many thousands of businesses still do not operate an effective data security system. As the size of hard disks grow and prices come down, many people take the view that backing up is either extremely time consuming or extremely expensive, and so they take a risk. But as more and more critical data is stored on these massive hard drives, the cost of replacing such data will make the cost of the most sophisticated backup system pale in comparison. Just sit back for a moment and try to imagine what the effect would be should your main file server go up in smoke today! Replacing the hardware would be the least of your problems - any reputable supplier or maintenance company should be able to help you get physically up and running within a few hours. But where would you start when faced with the task of replacing your data? How long would the system be unavailable while you were attempting the salvage operation? What effect would this have on your daily operations? And, horror of horrors, what if you simply could not retrieve the data at all? Do you keep manual records of your debtors? How would you progress orders and get the cash in? How would you pay your employees? The list of questions goes on and on, and gets ever more horrifying as it does. The bottom line is that, assuming your company doesn't actually go out of business as a result of this disaster, the final cost in terms of time, temporary staff to cope with the increased manual workload and, possibly most important of all, lost orders and customer confidence, is far greater than the cost of implementing the most comprehensive backup solution. Of course, total catastrophes are rare. But personal catastrophes can be almost as devastating. The plight of the secretary who wants to retrieve a missing file from a month ago might not seem too important, but if she is the chairman’s PA you could be in big trouble. The thing is, of course, that backup is pretty low down on the priority list of most users too. Quite simply, they expect you as the network administrator to be able to lay your hands on just about every copy of every file they have ever written - even if those files are stored on their local hard disk. How can we manage our data? The explosion of networked data - ranging from traditional LAN storage (corporate documents, presentations, etc.) to distributed databases (e.g., inventory, financial, or personnel-related data) to application-specific data stores (such as e-mail message stores, directory services repositories, or internal Web sites) - has resulted in increasing storage demands and thus storage-related costs. The META Group projects LAN storage will increase at 40 per cent or more annually, and the massive growth of distributed databases will at least keep pace with file system data growth over the next several years. However, this information resides and continues to be deployed on disparate systems, creating additional difficulties in managing enterprise data from a centralised location. With the process of storage management encompassing so many disciplines (i.e., backup, recovery, data migration, tape management, and archiving), IT administrators are finding themselves devoting an increasing (and sometimes inordinate) amount of time to managing this data. Scope of duties may range from labelling and tracking tapes to restoring a lost file or directory to rebuilding entire servers. It is also becoming increasingly difficult to pinpoint the “owner” of a particular set of data in an organisation. That pile of documents and spreadsheets sitting over there in the corner of the disk is probably the responsibility of the LAN administrator. But what about the payroll and HR databases? They may belong to the database administrator. And what about the e-commerce system - a mixture of files and databases? Who takes responsibility for that one? Trying to accurately assess the true cost of rebuilding lost data is also extremely difficult. You have to include the physical cost of replacing media, time taken by the MIS team to perform the rebuild and - most important of all - lost production time while the end users wait for their data to be recovered. One thing is for certain, the more mission critical the application - as with engineering and production systems - the higher the cost involved in rebuilding. Whilst the actual cost of the data in terms of bits and bytes remains the same across all types of applications, the cost of not being able to ship your product out of the door can be enormous. Mainframe solutions rely on the huge reel-to-reel tape drives for backup, of the kind you usually see whirring away in the background on sci-fi B-movies. Far too expensive for PC use, most standalone users will resort to the humble floppy disk to backup small amounts of essential data. But with the much larger multi-gigabyte volumes available on today’s file servers – and even local desktops - a more efficient means of backup is required. Even client workstations have local hard disks running to tens of gigabytes these days, and with the latest server-based software allowing centralised backup of network clients, the destination device needs to be capable of storing many gigabytes of data in a single pass. We begin our journey into the world of Data Storage Management with a look at the backup issues facing most of today’s administrators Backup Issues When was the last time you backed up your hard disk ? What's more important is, when are you planning to do your next one ? Because Murphy's First Law of Computing states that your hard disk will fail just minutes before you planned to start it. There are many ways to back up your hard disk, ranging from the humble floppy through to the more expensive DAT's, optical disks and even second hard disk drives. Which method you choose depends on how important your data is, how much data you have to back up, and in what sort of time “window”. If you have a machine at home with a 6GB hard disk which you use mainly for completing jobs you started at work, you are hardly likely to want to spend thousands of pounds on a sophisticated backup system, especially since most of the files will exist on your work computer as well. However, if you are the manager responsible for a large network whose file server sports several 20GB drives, and on which your company relies totally, you are hopefully not going to trust that data to a few hundred 1.4MB floppy disks. No matter what your requirements, there is a backup solution to suit you. A combination of hardware and software which should not only be totally reliable, but should be as easy as possible to use - or else you simply will not use it! |
