The volume of data we must manage is rising steadily. But what is our management strategy? Nothing is deleted, and hardly anyone takes the time to go through and purge obsolete files, so we end up stockpiling everything… just in case (and often in multiple copies!) Should these hundreds of gigabytes or terabytes be saved on disk or on tape? Your data must be safeguarded to protect against computer failure, theft and manipulation errors (approximately 40% of data loss is the result of human error).
It all comes down to knowing which type of backup media to use.
Below is a table that compares the key points of a disk-based system with a tape-based system:
- Disk-based systems are gaining a solid foothold in the market.
- Tape-based systems, whether DAT, LTO, DLT or SDLT, are an old habit to break.
Below is a table that compares the key points of a disk-based system with a tape-based system:
- Disk-based systems are gaining a solid foothold in the market.
- Tape-based systems, whether DAT, LTO, DLT or SDLT, are an old habit to break.
Disk Solution
Tape Solution
Disks in a RAID configuration guarantee continuity of service: RAID technology enables two or more hard disks to work in parallel. If one disk fails, the other serves as a backup disk. The reputation of disks being fragile no longer applies. For even greater security, several disks can combine to operate in a RAID5 or RAID6 configuration.
Requires daily human intervention, unless a backup robot is put in charge of changing the cartridge every day. Many companies give this responsibility to an administrator, who has to remember every day. If the cartridge is forgotten for any reason, then no backup is made for that day. Continual operation places a great strain on the tapes; they begin to break down after about six months, and must be replaced soon thereafter. An ever-increasing number of tapes must be managed to handle the volume of data being saved.
Backups are quick and effortless to set up. Once a backup regime has been configured, backup operations are performed without any intervention, once daily or even several times a day if necessary. Backups are taken quickly and automatically; only a minimum number of backup windows are displayed to limit the impact on system availability. Users can access and configure their own backups. They can also schedule backups as often as they need. Users do not need to know where their backups are located. The storage capacity is easy to increase.
Backups are managed exclusively by the administrator. Users can neither configure their backups nor access them directly.
Backing up the data stored on mobile workstations is a challenge for tape systems. A backup robot is required, as is self-discipline on the part of the laptop users. Even when mobile workstations connect to the network, they cannot be backed up immediately because the backup schedule must be respected. Likewise, backing up data from remote sites is a complex operation.
Backing up mobile workstations, as well as data from remote sites is supported. As soon as the mobile workstation is connected to the network, a backup of its data can be taken.
Restoring files is simple, intuitive, speedy and guaranteed at all times. The data is available 24 hours a day, seven days a week. Users can restore files by themselves with their own search criteria.
More hassle is involved: you have to figure out which tape was used to back up a file or folder before it can be recovered, something which can easily take several hours. Only the administrator has access to the restored data. It frequently happens that the cartridge cannot be read.
Tape backups cannot be initiated on-the-fly. Backups are planned and launched by the scheduler. The version of the files selected for the backup will be frozen as of the moment when the backup process began.
With a disk backup system, it is possible to back up one or several files on-the-fly, directly on the backup media. On-demand backups can be initiated by any user authorized by the administrator.
A disk-based backup solution can offer a history of X days of your files (X being a length of time set by the administrator, which can be several months). Such flexibility enables you to restore a file in the exact state it was in at a specific date
Unless a large number of cassettes are available, a tape backup solution cannot elegantly support a lengthy history.
The backup server can be located on-site at the company or off-site (in a clean room, for example). The incremental backup technology works in the same way, bandwidth permitting, whether the server is on or off the client site. The backed-up data can be replicated on external disks whenever needed.
The tape drive is generally left on-site; however, the tapes can easily be taken off-site. Investing in a backup robot is necessary in order to automate tape backups.
The price of hard disks is falling. For large volumes of data, backing up on disks is emerging as the more economical solution since the disks remain in place and do not require rotation..
To be comprehensively thorough, you need a minimum of one tape per day, per week, per month and per year.
Backing up data on disks makes it possible to set up secured access to the backed up files. Users enjoy authorized, real-time access to their own files.
Backing up data on tapes does not allow the creation of user-specific access permissions. For this reason, an administrator must be assigned to all data recovery tasks. Access to the data is sequential, which means that all files leading up to the data to be restored must also be readable for the recovery operation to be successful.
An unbeatable level of virtually infinite system durability is achieved by placing the disks in a RAID configuration and monitoring the hardware components of the disks where the backed up data will be stored. Disks of the configuration are replaced as soon as they become defective. Data therefore remains permanently accessible, regardless of the age of the system or its disks. For example, by implementing three or four disks in a RAID5 or RAID6 array, defective disks are replaced progressively during a malfunction, and the data is losslessly and securely copied over to the new disks. The data’s security is continuously maintained.
Keeping the tapes working properly over an extended period of time is very challenging. The mechanical elements (the drive and the magnetic tapes) degrade very quickly. A backup cartridge can become unreadable with no visible signs; the failure only becomes apparent when an attempt is made to restore a file. A malfunction can be brought about simply by changing the aging drive or by the state of the worn-out tape being read.
XOPHOS Conseils Canada 2013
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