After completing this module, you should be able to:
- List existing backup methods and explain their evolution.
- Explain the importance of hard drive and controller feed speed on backup performance.
- Identify performance tuning issues of designing a secondary storage solution.
- Define backup and restore strategies.
- Identify backup and restore tape rotation schemes.
- Define archiving and Hierarchical Storage Management.
LAN speeds
The following table displays maximum and typical LAN speeds, which can be regarded as the upper limits to backup data transfer rates over a LAN.
SCSI-3
SCSI-3 defines new physical-level transports, IEEE 1394 and Fibre Channel, as a means of transporting SCSI data packets.
SCSI-3 defines a new low-voltage differential (LVD) SCSI specification. LVD SCSI is a technology that combines the advantages of both its predecessors. LVD uses differential signaling techniques instead of single-ended, making the bus more stable. It will support up to 15 devices on one cable and enables the use of external SCSI cabling up to 12m long.
Bus speeds are defined in the SCSI-3 protocols:
+ Ultra — Transfer rate of 20MHz (also called Fast-20 or F20). Ultra SCSI buses have a maximum transfer rate of 20MB/s for Narrow SCSI or 40MB/s for Wide SCSI.
+ Ultra2 — Transfer rate of 40MHz (also called Fast-40 or F40). Ultra2 SCSI buses use LVD and has a maximum transfer rate of 40MB/s for Narrow SCSI or 80MB/s for Wide SCSI.
+ Ultra3— Ultra160 SCSI is the generation of high-performance SCSI technology that offers data transfer speeds of up to 160MB/s.
+ Ultra320— Ultra320 SCSI is the generation of high-performance SCSI technology that offers data transfer speeds of up to 320MB/s.
Backup Speeds and Feeds
The feed speed is the rate at which data is transferred to a tape drive. Feed speed is dependent on many factors, which are discussed later in this module. The write speed is the rate at which a tape drive transfers data to a tape.
The HP engineering team in Houston quantified the performance of the entire backup solution and its components. Basic speeds and feeds of the solution were tested. In order to achieve optimal backup performance, a 3:1 feed speed to write speed ratio is necessary for tape drives. If the feed speed to write speed ratio is less than 2:1, the tape drive performance may be halved.
The HP engineering team in Houston quantified the performance of the entire backup solution and its components. Basic speeds and feeds of the solution were tested. In order to achieve optimal backup performance, a 3:1 feed speed to write speed ratio is necessary for tape drives. If the feed speed to write speed ratio is less than 2:1, the tape drive performance may be halved.
Array Controller
The controller for the primary storage helps determine how quickly data can be retrieved from the system. The following table lists transfer rates for some of the array controllers.
Compression Ratio and Data Verification
The optimal backup solution is one that performs backups while other tasks are processing on the system. It must do this with minimal processor use to enable those other tasks to continue processing. This means that the backup solution should have hardware (rather than software) data compression and read-whilewrite data verification to ensure data integrity without affecting the performance of the system or the backup devices.
Hardware data compression means that compressing data for efficient storage on the backup device does not require use of the server’s processor, which would slow performance of other transactions on the server.
Read-while-write data verification means that when data is recorded to tape, parity checks and other forms of data verification occur concurrently with the writing of the data itself. This enables smooth streaming of data and continuous recording, even when errors are being discovered and corrected.
Speed
Performance needs are determined by dividing the amount of information (in gigabytes) that must be backed up by the size of the backup window (in hours). This simple calculation yields the required performance as an overall transfer rate expressed in GB/hr.
HP Tape Drive Specifications
For you to begin working with the required transfer rate formula, the table on the next page shows the following specifications on some of the HP tape drives:
+ The maximum capacity of uncompressed data each drive can store on a cassette
+ The transfer rates for reading and writing uncompressed data with each drive
+ Transfer rates when performing a local backup using each drive in a system
+ The estimated time for that system to perform a 100GB backup using each of the drives
+ The number of tape cartridges that will have to be loaded and unloaded during the backup operation
The Backup Window
the amount of time the company can afford to take servers offline each night for performing backups (if indeed they need to perform an offline backup).
Example
You need to provide local backup support for the ProLiant ML370 Server shown in the table to have 30GB of data to back up. Your backup window is four hours. What performance is required to deliver this kind of backup within the available time?
30GB ÷ 4 hours = 7.5GB/hr performance required
Three HP tape drives can transfer the data quickly enough to complete the backup in the allowable backup window: the HP AIT 35GB Tape Drive (10GB/hr), the HP AIT 50GB Tape Drive (20GB/hr), and the HP 40/80GB DLT Drive (18.6GB/hr). All three are good choices, but the DLT drive might offer a smoother migration path toward bigger storage systems.
Capacity
+ DLT drives use simultaneous multichannel and multihead read/write technology to achieve capacities up to 40GB without compression. A DLT drive is the appropriate high-end backup solution for larger servers, especially those with storage of 40GB or more, owing to a wide range of tape array, mini-library, and large library options.
+ SDLT (Super DLT) drives offer backward-compatibility with DLT tapes and increase storage capacity and transfer rate by an order of magnitude. Storage capacity starts at 110GB without compression. The SDLT drive is appropriate for enterprise-class servers, owing to its capacity and transfer rates, as well as improved reliability over DLT.
+ Ultrium drives offer outstanding reliability, excellent capacity, and data rate matching technology to optimize performance. Cartridge memory helps improve media management and reduce wear.
Hardware Reliability
The best method for building hardware reliability into a backup strategy is to ensure that the backup hardware is matched to the servers. The following table relates various servers with the appropriate tape drives. If the company needs special, partial backups in addition to the routine backups, it might be appropriate to select the next larger drive size.
Another factor to consider is media life. The following table lists the typical life for the various media discussed in this module.
Backup Strategies
Backup strategies are determined by asking the following questions:
+ Is the backup full or partial?
+ Is the backup image- or file-based?
+ How big are the backup and restore windows?
+ How often should backups take place?
Full Backup:
A full backup is a complete backup of the entire server or PC client hard drive. For a server, this includes all volumes, directories, and files. For a PC client, this includes all drives, directories, and files. Full backups can be further categorized as normal or copy backups:
+ Normal backup — Backs up files and resets the archive bit. The archive bit is used to determine if the file has been backed up or not.
+ Copy backup — Is similar to a normal backup except that it does not reset the archive bit.
Partial Backup
A partial backup can be any of the following:
+ Incremental
+ Differential
+ User-defined
Rotating Tapes - Grandfather-Father-Son Tape Rotation
The name GFS refers to three levels of backup:
+ Monthly grandfathers
+ Weekly fathers
+ Daily sons
Typically, the system administrator performs a full backup every Monday (father) and does incremental backups on Tuesdays, Wednesdays, and Thursdays (sons). The administrator performs another full backup at the end of the week (father) and yet another at the end of the month (grandfather).
Typical Monthly GFS Backup Schedule
No weekend activity is shown in the calendar. However:
+ If any mission-critical development is done over a weekend, the network administrator is notified to schedule one or two additional special backups.
+ If the last day in the month is a Saturday or Sunday, the grandfather backup takes place on that day.
The optimal backup solution is one that performs backups while other tasks are processing on the system. It must do this with minimal processor use to enable those other tasks to continue processing. This means that the backup solution should have hardware (rather than software) data compression and read-whilewrite data verification to ensure data integrity without affecting the performance of the system or the backup devices.
Hardware data compression means that compressing data for efficient storage on the backup device does not require use of the server’s processor, which would slow performance of other transactions on the server.
Read-while-write data verification means that when data is recorded to tape, parity checks and other forms of data verification occur concurrently with the writing of the data itself. This enables smooth streaming of data and continuous recording, even when errors are being discovered and corrected.
Speed
Performance needs are determined by dividing the amount of information (in gigabytes) that must be backed up by the size of the backup window (in hours). This simple calculation yields the required performance as an overall transfer rate expressed in GB/hr.
HP Tape Drive Specifications
For you to begin working with the required transfer rate formula, the table on the next page shows the following specifications on some of the HP tape drives:
+ The maximum capacity of uncompressed data each drive can store on a cassette
+ The transfer rates for reading and writing uncompressed data with each drive
+ Transfer rates when performing a local backup using each drive in a system
+ The estimated time for that system to perform a 100GB backup using each of the drives
+ The number of tape cartridges that will have to be loaded and unloaded during the backup operation
the amount of time the company can afford to take servers offline each night for performing backups (if indeed they need to perform an offline backup).
You need to provide local backup support for the ProLiant ML370 Server shown in the table to have 30GB of data to back up. Your backup window is four hours. What performance is required to deliver this kind of backup within the available time?
30GB ÷ 4 hours = 7.5GB/hr performance required
Three HP tape drives can transfer the data quickly enough to complete the backup in the allowable backup window: the HP AIT 35GB Tape Drive (10GB/hr), the HP AIT 50GB Tape Drive (20GB/hr), and the HP 40/80GB DLT Drive (18.6GB/hr). All three are good choices, but the DLT drive might offer a smoother migration path toward bigger storage systems.
Capacity
+ DLT drives use simultaneous multichannel and multihead read/write technology to achieve capacities up to 40GB without compression. A DLT drive is the appropriate high-end backup solution for larger servers, especially those with storage of 40GB or more, owing to a wide range of tape array, mini-library, and large library options.
+ SDLT (Super DLT) drives offer backward-compatibility with DLT tapes and increase storage capacity and transfer rate by an order of magnitude. Storage capacity starts at 110GB without compression. The SDLT drive is appropriate for enterprise-class servers, owing to its capacity and transfer rates, as well as improved reliability over DLT.
+ Ultrium drives offer outstanding reliability, excellent capacity, and data rate matching technology to optimize performance. Cartridge memory helps improve media management and reduce wear.
Hardware Reliability
The best method for building hardware reliability into a backup strategy is to ensure that the backup hardware is matched to the servers. The following table relates various servers with the appropriate tape drives. If the company needs special, partial backups in addition to the routine backups, it might be appropriate to select the next larger drive size.
Backup strategies are determined by asking the following questions:
+ Is the backup full or partial?
+ Is the backup image- or file-based?
+ How big are the backup and restore windows?
+ How often should backups take place?
Full Backup:
A full backup is a complete backup of the entire server or PC client hard drive. For a server, this includes all volumes, directories, and files. For a PC client, this includes all drives, directories, and files. Full backups can be further categorized as normal or copy backups:
+ Normal backup — Backs up files and resets the archive bit. The archive bit is used to determine if the file has been backed up or not.
+ Copy backup — Is similar to a normal backup except that it does not reset the archive bit.
Partial Backup
A partial backup can be any of the following:
+ Incremental
+ Differential
+ User-defined
Rotating Tapes - Grandfather-Father-Son Tape Rotation
The name GFS refers to three levels of backup:
+ Monthly grandfathers
+ Weekly fathers
+ Daily sons
Typically, the system administrator performs a full backup every Monday (father) and does incremental backups on Tuesdays, Wednesdays, and Thursdays (sons). The administrator performs another full backup at the end of the week (father) and yet another at the end of the month (grandfather).
Typical Monthly GFS Backup Schedule
+ If any mission-critical development is done over a weekend, the network administrator is notified to schedule one or two additional special backups.
+ If the last day in the month is a Saturday or Sunday, the grandfather backup takes place on that day.
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