One of the most common chores for a network administra= tor is protecting data by ensuring that backup copies exist. As we discussed last time, this is part of an overall disaster recovery plan. Backups are extrem= ely important for the obvious reason, if the original gets corrupted, deleted, = or lost due to some sort of mishap (user error, virus, hardware failure, etc.)= , it cannot be replaced without a backup copy. Therefore, in continuation of our look at disaster recovery, we will focus this time around on backup technologies and what data you should be looking at backing up on your netw= ork. In the next installment we’ll continue our discussion of backups to examine specific backup types and establishing a schedule for backing up da= ta and handling backup media.
Storage technology has grown quite a bit over the last= few years, and now there are multiple options available when it comes to storag= e. Some of these are:
* &nb= sp; Storage Area Networks
* &nb= sp; Removable Storage Drives
* &nb= sp; Tape
Storage Area Networks, or SANs, draw their origin to t= he mainframe days. However, they have really only come into prominence in the world of client/server networking in the last few years. Rather than having a storage device attached to each individual serv= er you have a collection of storage devices linked together and connected to b= ack to the network through a switch and high speed fiber channel or Gigabyte Et= hernet connections. While costs are initially quite expensive, in the tens of thousands of dollars to get setup, performance is greatly improved since yo= ur servers don’t spend as much time processing basic I/O requests for da= ta from user workstations. Improved performance increases efficiency and lowers overall costs. The speed ensures that data is always available, an advantage over traditional storage devices that backup to media such as tape. With th= ose technologies data that isn’t still on the server due to disk space us= age must be restored from a tape or similar media before it can be accessed. Wi= th storage centrally managed and the storage devices backing each other up for redundance, reliability is greatly strengthened.
An additional benefit is what is called near-line s= torage. This is media that is too slow to work directly off of in an efficient mann= er, but is fast enough to make data quickly available in the event a restore is needed. If you’ve ever had to access a backup from a tape solution, y= ou know that even retrieving a single file can take several minutes. That is said t= o be off-line storage because the nature of it is such that you’re = not going to be able to quickly retrieve data from the tape on the fly if neede= d. Even though software exists that allows you to access a tape drive through a drive letter, this still would not qualify as near-line. Media such as hard drives and even floppy drives or CD-RW drives are fast enough that you can = work from them directly. Think of near-line storage as being in between these two speeds. Another feature of near-line storage is that the data is available without the intervention of an administrator to restore files for the user. That is, no special programs have to be run to “restore” the da= ta. A user with permissions can access the backup directly, though again it wou= ld be too slow to work directly with the files in this manner.
Removable storage drive such as those made by Iomega h= ave grown in popularity in recent years as the media costs have come down and d= ata files are often too large to fit on a single floppy disk anymore. The technologies start with floppy drive replacements such as the LS-120 Superdisks, which are 120MB floppy drives that can also read standard 1.44MB floppies, to Iomega Zip drives at 100-250MB capacity and. Recordable CD-ROM drives and Rewritable CD-ROM drives also fit into this category of removable storage. From there they move onto hard drive capacities and speed such as = with Iomega’s Jaz drive. These technologies are better suited to world of workstation backups though because of their capacities. Backing up a multiple Gigabyte hard drive would require several disks and would making backups even more tediou= s.
For all of the criticism tape drives get for their lac= k of speed, tapes still offer the most bang for the buck when it comes to price = per megabyte, usually costing around $.03-$.05 per megabyte. That price point a= nd their wide availability make tapes the overwhelming choice for the vast majority of companies. Tape drive speeds have dramatically increased as technology has advanced, and some drives today will backup at a rate of well over 100MB of data per minute. DAT and DLT drives are the most popular type= of tape drives on the market.
Tape drives work the same way cassette recorders work,= data is read or written sequentially as the tape passes over the heads of the dr= ive. This fact makes restoring data sometimes take a lot longer than you think it should. For instance, if you need to restore a 30K word document that a user accidentally deleted, the drive has to read the tape until it comes to the = file it is looking for. There are software packages that exist that actually give the tape drive a drive letter on the system it is attached to, however, the speed is why we referred to tape as off-line storage. That means that the data is not available in a manner that makes it efficient to work with = it directly off of that particular media.
For our purposes we are going to assume your backup st= rategy will involve the use of tape drives and tape media since that is what is in= use by the vast majority of companies today. Once you have your backup hardware= in place, you have to decide how exactly you are going to do your backups. As = was mentioned earlier, there is more to a backup strategy than just feeding tap= es and walking away. The first step in planning is to determine what exactly i= t is that you are going to backup. That will help you decide of the appropriate backup method. We will focus on determining what to backup in this article,= and then cover the backup methods next time.
The different types of files on a network to be backed= up are:
* &nb= sp; Operating System Files and Settings
* &nb= sp; Applications
* &nb= sp; User Data Files
Operating system files are the files that are essentia= l to the operation of the machine. Because without an operating system there is nothing for your computer to do when you turn it on, the OS is of vital concern. The Windows Registry maintains system configuration settings that Windows and its applications refer to during its operation. It also maintai= ns security and policy information as well as the hardware device settings of = the system. Part of the backup process for Windows NT/2000 machines is creating emergency repair disks (ERDs) to backup this type of information. Even with having up to date ERDs though you will still want to have the data files themselves backed up to tape for the possibility of future restore.
Applications are not just the programs users access and run from the server, but also the applications such as the backup software that you run on the server. In most cases applications do not need= to be specifically backed up unless it is part of an overall scheme of perform= ing full backups. If you are not backing up applications, ensure that you have = any special configuration settings documented and kept with your original installation media. Additionally, you want to be extra careful that you hav= e an a plan involving where application CDs are stored, what patches or fixes are required to be installed along with the applications, and the information required for installation such as a service account name and password. This should all be documented and kept up to date as versions change and updates= are released.
Arguably the most important of the files to backup, th= ese are the files that cannot be reinstalled from a vendor’s diskette or CD-ROM. User data is the company’s livelihood and is what you are the= re to protect. You should have a network design in place where users at minimu= m back up their data to a central server location on a regular basis, and preferab= ly store and work from their data files directly from a server. Life will be m= uch easier on you as a network administrator this way, rather than if you have = to attempt to track down data files to user hard drives and various locations = on a server.
In addition to backing up files on the server to tape,= it is wise to also train users in saving their files to a floppy disk whenever possible. Not only does doing that give the user quick access to their file= s if they delete or accidentally damage the one on the server, it also provides = an extra layer of protection in case the tape drive fails or otherwise canR= 17;t read the tape media to restore the files.
Once you have determined what it that you want to back= up, whether it is just user data, or the entire server, you are ready to start designing your backup strategy based on the different types of backup metho= ds available. Next time around we will examine the types of backups you can perform, and how to create a schedule that provides good security against d= ata loss in the case of any number of disasters.
Questions or Comments?
Will can be reached at WWillis@Transcender.com