Scsi Cdrw
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PC Hardware in a Nutshell (In a Nutshell (O’Reilly))
£28.50
PC Hardware in a Nutshell relies on an eternal truth of the computer industry: legacy systems never die. This book focuses on the technologies that have provided Wintel personal computers with various capabilities over the years. Like most of its competitors, this book addresses the PC on a subsystem level, dealing with video cards, hard-disk interfaces, memory and other pieces of the componentry …
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Creating a Backup Strategy to avoid Disaster
Organize your data so it is easy to back up.
You want all your data files (e.g. Word documents, Excel documents, email, etc.) to be in folders that are all inside a single folder on your hard disk. Windows provides you with a folder named “My Documents” designed for this purpose. In Windows 95/98/ME there is a single My Documents folder shared by all users while Windows NT/2000/XP creates a separate My Documents folder for each login account. Backing up the “WinNTProfiles” folder in NT 4.0 or the “Documents and Settings” folder in Windows 2000/XP will back up the My Documents folders for all users if you are logged in as an administrator.
Many programs default to saving files in the My Documents folder and programs that can’t can usually be set to do so. You will probably want to create new folders under the My Documents folder to keep data from different applications or projects separate. You may need to read the documentation to learn how, but you should set each program to open documents from and save documents to the appropriate folders you have created under the My Documents folder. If you do this consistently you will know where all your data is on your hard disk and won’t accidentally miss backing up important data.
Choose what device you will use to back up your data.
The most common devices to back up data have been tape drives, zip drives and flash drives. More recently, CDRW drives (CD read/write drives) are being used for backups. Your decision will be based on how much data you need to back up, what devices you already have that could be used for backups, and whether or not you can purchase a new backup device.
The least expensive devices are Iomega zip drives and disks. Zip disks come in 250MB and 100MB sizes. You must buy a zip drive designed for 250MB disks to use 250MB disks. All zip drives can work with 100MB zip disks. Zip drives come with software for backing up data to zip disks or you can copy the folder that all your data is under (“My Documents” or “Documents and Settings” to a zip disk if it will all fit.
Jaz drives come in 1GB and 2GB sizes and are similar to zip drives but are bigger and cost more. They use the same Iomega backup software as zip drives. You can also use DVD disks which are 4.7gig in size.
CDRW drives can be used like a 650MB floppy disk when using CDRW disks and packet writing software that comes with the drive. The disks you create will be readable only on other CDRW drives or CDR/DVD drives that support the multi-thread standard. All drives capable of reading CDRW disks require software to be installed that supports reading CDRW disks. You should use software that supports the UDF standard (most current CDRW packet writing software does) when writing files on your CDRW drive and install UDF reader software on computers with multithread CD or DVD drives that you want to read CDRW disks. Drives with early implementations of multithread may not be able to read CDRW disks even with UDF reader software installed. Free UDF readers are available from Ahead Software and Roxio. CDRW drives may come with backup or disaster recovery software but you should look carefully at the software bundled with a CDRW drive before purchasing it.
Unlike the previous devices, tape drives are designed specifically for backing up data. They hold more data, 4GB to more than 40GB, and require running a backup program both to backup or restore files. A tape drive cannot be used like a large floppy disk. Windows 95/98/ME does not come with backup software so you must use the software, if any, that comes with the tape drive, or purchase backup software. Windows NT has a backup program that works with most SCSI tape drives. Windows 2000/XP has a backup program that works with any removable media that can be written to from within Windows (e.g. zip, jaz, CDRW) and most tape drives. Tape is the least expensive media for very large amounts of data.
Develop a backup strategy.
You can just copy the files you need backed up onto removable media. This cannot be done with tape, but works with zip, jaz, and CDWR disks. It only works well if all your data fits on a single disk. Using a backup program allows using tape and can span more than one disk or tape if necessary. Backup programs also allow special backup series starting with a complete backup followed by backing up only files that have changed. Initially, assume doing complete backups. Ideally, you should back up your data on a daily basis. This guarantees that you won’t lose more than one day’s work if your hard disk crashes. In the strategies below, it also means you aren’t completely dependent on any one disk or tape for your backups. Removable disks and tapes also go bad.
Strategy One: Gives you one work week of daily backups.
Label five media (disks or tapes) Monday, Tuesday, …, Friday.
On a Monday, put Monday’s media into its drive then copy/backup your “My Documents” folder or “Documents and Settings” folder to the media. Remove the media when all the files have been saved to it.
Repeat step 2 daily using the appropriately labelled media for each day. Erase the data on the backup media from the previous week either manually or through the backup program you are using before performing a new backup to it.
Strategy Two: This is an extension of Strategy One. It gives you one work week of daily backups plus one month of weekly backups.
Label four media Tuesday, Wednesday, Thursday, Friday.
Label five media 1st Monday, 2nd Monday, …, 5th Monday.
On the first Monday of the month, delete any data already on your 1st Monday media then backup your data to it.
Backups on Tuesday through Friday will be the same as in Strategy One.
On the second, third, fourth, and fifth (if there is one) Monday of the month you would delete previous data then perform a current back up to the media labelled for that Monday.
Strategy Three: This is an extension of Strategy Two. It adds a year of monthly backups.
Replace the 1st Monday media in Strategy Two with 12 media labelled January, February, …, December. On the first Monday of each month use the media labelled for that month erasing the data from the previous backup to that media. All other days of the month are as in Strategy Two.
Strategy Four: This is the minimalist backup strategy and is a cut down version of Strategy One. Use two media rather than five and label them A and B. Back up your data files daily alternating between the two media. This protects you against hard disk failure but not against viruses. Destructive viruses often go undetected for relatively long periods of time and you may need a backup that goes back days or weeks to recover data damaged by a virus. You should never use only one disk or tape for backups. All media can fail so you should have at least two backups in addition to working copies of your data.
Strategy Five: This is the easiest strategy if it’s available to you. If you are faculty or staff at a university and your computer is on a LAN (local area network), you may be able to keep your files on a LAN file server where files are backed up to tape every night. Check with your local computer support group to see if this is the case and what restrictions or costs might be in place.
Which strategy to use depends on how far back in time you want to be able to restore data from and how much effort you are willing to devote to backups. Strategy Three is no more work than Strategy One, but requires more media and slightly more organization. If you use backup software you may be able to use partial backups that are called incremental and differential backups. Both start by doing a full backup followed by:
Incremental backups: They copy only files that have changed since the last backup into a new backup set. This is the most space efficient backup type but is the most difficult to do restores from. You might be able to do a full backup plus four incremental backups on a single media. If so, you would only need one disk or tape per week but might need to look in five different backup sets to find the right one to restore a file from. A complete restore requires restoring all five backup sets. Using incremental backups this way would lose a week’s worth of backups if the media goes bad.
Differential backups: They copy all files that have changed since the last full backup into a new backup set. This means you only need to look in the full backup set and the most recent differential backup set to find the most recent version of a file. You only need to restore the full backup set and the most recent differential backup set to know you have the most recent version of all your data. Like the incremental backups, you might be able to put a full week of backups onto a single disk or tape and risk losing a full week of backup files if the media goes bad.
Complete backups on a daily basis are easiest to restore from. You use your most recent backup to recover the most recent version of a data file or go back to the previous backup that is appropriate if you want an earlier version of the file.
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