40 Questions
What is the primary advantage of data compression in communication systems?
Enabling devices to transmit or store the same amount of data in fewer bits
What type of compression is used in formats like JPG and MP3?
Lossy compression
What is the primary purpose of the 3-2-1 backup strategy?
To provide multiple copies of data on different media
What was the consequence of UniSuper pension fund's cloud provider configuring services incorrectly?
Two backup copies on Google Cloud were lost
What is the primary benefit of using lossless compression formats like FLAC and TIFF?
Improved data quality
What is the primary goal of a backup strategy?
To provide a way to restore data
What is the effect of compressing a 1MB plain text file to 35% of its original size?
Data transfer time decreases by 50%
What is the primary advantage of using a 3-2-1 backup strategy with a different provider?
Reduced reliance on a single provider
What is a major concern with solid or multi-volume archives?
They can be lost with even minor data corruption
What is the primary drawback of lossy compression?
It reduces the quality of the data
What is the purpose of RAID 1?
To pair drives for redundancy
What is the difference between a full and differential backup?
A full backup includes all files, while a differential backup includes only changed files
What is the primary advantage of using incremental backups?
They are faster than differential backups
What is the primary concern with using a single cloud provider for data storage?
The risk of a single point of failure
What is the purpose of redundant array of independent disks (RAID)?
To improve data integrity
What is a characteristic of a backup?
It is a copy in a geographically separate location
What is the primary purpose of data deduplication and Single-instance storage in backup systems?
to eliminate duplicate copies of data within and across systems
Which of the following is NOT a characteristic of a good backup strategy?
two-way synchronization
What is the main difference between a full backup and an incremental backup?
full backup captures all data, incremental backup captures only changed data
What is the purpose of the 3-2-1 Backup Checklist?
to ensure multiple copies of data in different formats and locations
What is the main advantage of using LTO tape or optical disc libraries as nearline tertiary storage?
they are platform independent and can be moved offsite
What is the main difference between user-level file recovery and backup?
user-level file recovery is not a backup strategy, it's a way to recover individual files
What is the main disadvantage of using Windows Recycle Bin or macOS Trash as a backup strategy?
it's only good for short-term recovery
What is the main advantage of using AWS Glacier or Google Nearline as a cloud storage option?
they are inexpensive for upload storage
What is the primary purpose of minimizing redundancy in file compression?
To reduce the size of the compressed file
What type of compression is suitable for applications requiring high-quality output, such as medical imaging?
Lossless compression
What is the primary advantage of using a 3-2-1 backup strategy?
Improved data integrity
What is the purpose of using encryption in file compression?
To enhance the security of the compressed data
What is the primary benefit of using ZIP archives for cross-platform file exchange?
Platform-independent file exchange
What is the primary purpose of using RAID in data storage?
To improve data integrity
What is the primary consequence of data corruption in a compressed file?
Data loss or corruption
What is the primary benefit of using lossless compression formats like FLAC and TIFF?
Preservation of original data quality
What is the primary reason why user-created files need to be backed up?
To recover from accidental deletions
Which backup strategy is used when a system operator or backup software runs a backup at specific times?
Scheduled
What is the main disadvantage of using local backup media?
If the computer is lost or malfunctions, the data is also lost
Why is manual backup considered the least effective method?
It relies on the user to perform the backup
What is the primary advantage of using external backup media?
It provides a safe off-site storage location
What is the main difference between local and external backup media?
Local backup is stored on the computer, while external backup is stored on a separate device
Why is network backup considered a slower option for large backups?
It has a lower throughput than directly attached devices
What is the primary advantage of using automatic backup software?
It continuously monitors for file changes
Study Notes
Servers and Archives
- Archived files must be uncompressed before use, requiring extra space for both compression and decompression.
- Data corruption can cause loss of the entire archive, and even minor corruption can result in loss of solid or multi-volume archives.
- Archive repair is possible but not probable, so it's essential to test archives to confirm integrity.
Why We Need Backups
- Accidental deletion by users or IT people is a common cause of data loss, accounting for 2/3 to 3/4 of all data loss.
- Hardware failure is another significant cause of data loss, as all storage devices will eventually fail.
- Less frequent causes of data loss include catastrophes, account cancellation or accidental closure, and single-point failure of cloud service providers.
Continuous Data Integrity
- Redundant Array of Independent Disks (RAID) ensures continuous data integrity by tolerating drive failure.
- RAID 1 pairs drives, RAID 5 uses +1 parity drive, and RAID 6 uses +2 parity drives, all providing redundant data storage.
- RAID appears as one logical drive space to the OS, excluding parity drives.
Characteristics of a Backup
- A backup is a copy of data in a geographically separate location that is platform-independent.
- Classic file backup strategies include Full, Differential, and Incremental backups.
- Full backup is slow, Differential backup is faster, and Incremental backup is faster than Differential, but restore is slowest.
One-Way Backup to Cloud Cold Storage
- One off-site backup (geographically separate location) is essential, using cloud storage that is different from your cloud service provider.
- Tape/optical media can be used to rotate Full, Differential, and Incremental backups to off-site storage services.
UniSuper Pension Fund Case Study
- UniSuper pension fund, with USD $125 billion and 647,000 members, experienced a near loss of data due to a cloud provider's configuration error.
- Fortunately, the fund had a proper 3-2-1 backup with a different provider, which enabled them to restore services.
The Final Word on Backups
- Backups do not matter; only restore matters.
Effect of File Compression on Data Transfer
- File compression can significantly reduce data transfer time and size.
- For example, compressing a 1MB plain text file to 35% of its original size can reduce transfer time from 16.6 hours to 8.3 hours.
File Compression Formats
- Lossless compression formats include TIFF, PNG, GIF, and FLAC.
- Lossy compression formats include JPG, MP3, AAC, MP4, MPG, and DIVX.
How Compression Works
- Data compression enables devices to transmit or store the same amount of data in fewer bits.
- There are various data compression techniques, but only a few have been standardized.
Enterprise Backup
- Backup software uses Full, Differential, and Incremental strategies.
- Options for file versions/generations and periodic snapshots are available.
- Enterprise OS provides for backup of continuously running systems, and LTO tape or optical disc libraries can be used as nearline tertiary storage.
User Level File Recovery
- Windows File History and macOS Time Machine are not exactly backups, but they can be used for file recovery.
- Automatic copying of files to external or network drives can be used for file recovery.
- However, these methods are not true backups, as they are not geographically separate or platform-independent.
3-2-1 Backup Checklist
- 3 copies: 1 active, 1 local backup, and 1 remote backup.
- 2 different formats/platforms: platform independence.
- 1 off-site backup: having a backup will allow you to recover from lost, broken, or stolen hardware, and from accidental deletions.
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