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RPO (Recovery Point Objective) The maximum acceptable time period that data can be lost prior to a disaster. The RPO determines at what point your data can be fully restored in the event of a disaster. An RPO of one hour means you should be able to recover any data changes made up the 60 minutes before a disaster.
RTO (Recovery Time Objective) The maximum acceptable time period required to bring data, processes, applications or systems back into full use after a disaster. Sometimes referred to as Maximum Allowable Downtime.
Shoe Shining Term used to describe a process whereby the data supplied to a tape drive is at a rate slower than the drive’s optimal writing speed. As a result, the tape is constantly slowed down, stopped, rewound and restarted. This back-and- forth motion is similar to the act of polishing shoes, hence the expression. Excessive shoe shining can cause wear on both drive and tape.
Shelf Term used to describe the disk housing of a SAN, which can contain multiple disks. Generally, it is possible to expand SAN solutions by adding shelves. The shelf usually does not contain any intelligence; it only provides additional disk space.
SIS (Single Instance Storage) A de-duplication process developed by Microsoft, which removes identical copies of stored files to increase available storage space. See expanded explanation.
Recovery Point Objective (RPO)
The maximum acceptable time period that data can be lost prior to a disaster. The RPO determines at what point your data can be fully restored in the event of a disaster.
Last full backup Recovery Time Objective (RTO)
The maximum acceptable time period required to bring data, processes, applications or systems back into full use after a disaster. Activities include fault fixing, system recovery, testing and communication to the network users
Failure or disaster Service back online
SAN (Storage Area Network) A centralised pool of disk storage which connects to multiple servers. See expanded explanation.
SAS (Serial Attached SCSI) An enterprise-grade hard disk technology. See expanded explanation.
SATA (Serial ATA) A high-capacity, low-cost disk technology. See expanded explanation.
SCSI (Small Computer System Interface) Hardware interface used for connecting hard disk drives to a computer or server. SCSI allows up to 15 devices to be connected to a SCSI host adapter and supports data transmission rates of up 80MBps.
Serverless Backup A system which bypasses the server during the backup process, by using a Fibre Channel or iSCSI connection to link a SAN directly to a tape unit. The technology has much potential in education, but it is currently too expensive for most schools to consider.
SFP (Small Form-Factor Pluggable) A hot swappable optical modular transceiver designed for use with small form-factor connectors. The modular nature of SFP transceivers makes it easier to upgrade a fibre optic network.
Snapshot Process whereby a point-in-time copy of the data is made. Snapshotting can help protect your data, and various types of snapshot technologies are available, including Copy-on-write and Continuous Data Protection. See expanded explanation.
Software Compression The use of software to compress data. Software compression is slower than hardware compression and can make demands on system resources (especially the CPU). For these reasons, software compression is rarely implemented.
SPS (Standby Power Supply) Usually, a battery installed inside or attached to a SAN. In the event of a power failure, the SPS allows the SAN to continue to function.
SSD (Solid State Drive) A data storage device which uses solid state memory to store data. Solid state drives offer a number of benefits over conventional hard disk drives including, faster start-up times, faster access times, no moving parts, low noise and no risk of mechanical failure. However, they are more expensive, have lower capacities and have a limited lifetime, typically offering 30,000-1 million write cycles per block, depending on the quality of the flash chip. For these reasons, hard disk drives remain the most cost effective storage solution for schools.
Switch High speed interconnection device which controls port-to-port transfers between nodes. In Fibre Channel switched fabric, host computers and storage devices are connected to each other through Fibre Channel switches. iSCSI systems utilise Ethernet switches.
Tape Library A storage system which uses one or more tape drives and racks of magnetic tape cartridges. Many tape drives are automated and use robotic arms to load and unload the tape cartridges. Tape libraries can store vast amounts of data and are scalable, making them ideal for use as a data backup store.
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