Thought stream

SAN: Enhance storage devices - Disk arrays and tapes SANs make disk arrays and tape libraries accessible to servers so that the devices appear to the OS as locally attached devices; SAN is a separate network of storage devices not accessible through LAN by other devices. NAS: A single device or server or computing appliance, sharing its own storage over the network. iSCSI: Transports block-level data between an iSCSI initiator on a server and and iSCSI target on a storage device. The protocol encapsulates SCSI commands, assembles the data packets for the TCP/IP layer. Packets are transferred using point-to-point connection. Bastion host is a special purpose computer on a network specifically designed and configured to withstand attacks, generally hosts single application. Ex. a proxy server, and all other services are removed or limited to reduce the threat to the computer. Source: Wikipedia

Standard RAID levels comprise of configurations that employ the techniques of * STRIPING * MIRRORING * PARITY  to create large reliable data stores using general purpose HDDs. Levels are standardized by SNIA (Storage Networking Industry Association) in Common RAID Disk Drive Format (DDF) RAID 0 >> STRIPING (No fail-over, No Redundancy, Total loss of information if disk fails, each disk size will be of smallest disk size in the set of the disks) RAID 1 and its variants >> MIRRORING (Copy of write will be in more than one disk, Redundancy, less performant) RAID 5 >> Distributed PARITY RAID 6 >> Dual PARITY Source:   Wikipedia

Points to keep in mind: 1. Computers that belong to a subnet are addressed with an identical most-sig bit group in the IP addresses 2. IP is logically divided into NetworkIdentifier/Routingprefix and Restfield/HostIdentifier 3. Routing prefix can be expressed as CIDR (Classless Inter-Domain Routing) notation. Ex. 198.51.100.0/24 Implies NetworkIdentifier has 24 bits allocated and Rest field has 8 bits allocated 4. A network is characterized by subnet mask or netmask, applied by bitwise AND operation Ex. For 198.51.100.0/24, the subnet mask is 255.255.255.0 Subnet masks are used to identify the networks *If 198.51.100.0 is NetworkIdentifier, then 198.51.100.255 is BroadcastIdentifier For Class A, mask is 255.0.0.0; Class B, mask is 255.255.0.0; Class C, mask is 255.255.255.0 5. Traffic is exchanged between subnets through routers, when the routing prefixes of the source and destination addresses differ; A router serves as a logical boundary between the subnets. Advantag