Storage Overview

Learning Objectives Storage network technologies Types of storage system Fiber channels Fabric in storage Storage Area Networking Storage Virtualization

Storage networking technology Storage networking is the process of linking storage devices together and connecting to other IT networks and provides a centralized repository for data that can be accessed by users and uses high-speed connections to provide fast performance. Storage networking is used in reference to storage area networks (SANs) which links multiple storage devices and provides block-level storage. Storage networking can also refer to network attached storage (NAS) devices. NAS is a standalone device which connects to a network and provides file-level storage. The NAS unit typically does not use a keyboard or display and is controlled and configured over the network using a browser. An operating system is not needed on a NAs device and usually a stripped down operating system like FreeNAS is used. The Network Attached Storage uses file based protocols like NFS, SMB/CIFS and NCP.

Block Level Storage Block Level Storage - In this block level storage, raw volumes of storage are created and each block can be controlled as an individual hard drive. These Blocks are controlled by server based operating systems and each block can be individually formatted with the required file system. Block level storage is usually deployed in SAN or storage area network environment. Block level storage can be used to store files and can work as storage for special applications like databases, Virtual machine file systems and so on. Block level storage data transportation is much efficient and reliable. Block level storage supports individual formatting of file systems like NFS, NTFS or Server Message Block (SMB -Windows) or VMFS (VMware) which are required by the applications. Each storage volume can be treated as an independent disk drive and it can be controlled by external server operating system. Block level storage uses  Internet Small Computer Systems Interface (iSCSI) and Fibre Channel Over Ethernet (FCoE) protocols for data transfer as SCSI commands act as communication interface in between the initiator and the target.

File Level Storage  This storage technology is most commonly used for storage systems, which is found in hard drives, NAS systems and so on. In this File Level storage, the storage disk is configured with a protocol such as NFS or SMB/Common Internet File System(CIFS) and the files are stored and accessed from it in bulk. The File level storage is simple to use and implement. It stores files and folders and the visibility is the same to the clients accessing and to the system which stores it. This level storage is inexpensive to be maintained, when it is compared to its counterpart i.e. block level storage. Network attached storage systems usually depend on this file level storage. File level storage can handle access control, integrate integration with corporate directories; and so on.

Storage networking technology The Storage networking can include direct-attached storage (DAS), network-attached storage (NAS) and storage-area network (SANs). The interface technologies used in storage networking include Fibre Channel (FC), iSCSI and serial-attached SCSI (SAS). iSCSI is deployed in small and medium-sized businesses because of the low cost and simplicity and can also be scaled up with 10 GbE technology to be used with larger enterprises. Fibre Channels are used for its excellent performance, availability and scalability and is generally isolated from the LAN. Fibre Channels are commonly used in large data centres. Fibre Channel over Ethernet encapsulates FC protocol within Ethernet packets using a new technology called Data Center Bridging (DCB).

DAS vs. NAS vs. SAN Direct-attached storage (DAS) is digital storage directly attached to the computer accessing it, as opposed to storage accessed over a computer network. Examples of DAS include hard drives, optical disc drives, and storage on external drives. Network-attached storage (NAS) is a file-level computer data storage server connected to a computer network providing data access to a heterogeneous group of clients. NAS is specialized for serving files either by its hardware, software, or configuration. A storage area network (SAN) is a network which provides access to consolidated, block level data storage. SANs are primarily used to enhance storage devices, such as disk arrays, tape libraries, and optical jukeboxes, accessible to servers so that the devices appear to the operating system as locally attached devices.

Benefits of Storage Networking The benefits of storage networking are: improved performance, reliability and availability and also make it easier to back up data for disaster recovery purpose. Storage networks are often used in parallel to storage management technologies like storage resource management software, virtualization and compression.

Types of Storage System Storage is a technology consisting of components and recording media to retain digital data for the purpose of future usage. It is a core function and fundamental component of computers. All computers use a storage hierarchy which puts expensive and small storage options into the CPU. The volatile technologies are referred to as memory and the slow permanent technologies are referred to as Storage. The computer represents data using binary numeral system. Text, numbers, pictures, audio are converted into string of bits or binary digits having value of 0 or 1. Storage in a Computer is measured usually in bytes, Kilobytes(KB), Megabytes(MB), Gigabytes(GB) and presently in Terabytes(TB).

Types of Storage Primary Storage : Secondary Storage : Primary storage is also known as memory, which is directly accessible to the CPU. The CPU continuously reads the instructions which is stored and executes them as and when required. RAM, ROM and Cache memory are examples of primary memory. Secondary Storage : Secondary storage is also referred to as external memory or auxiliary storage and is the one which is not directly accessible by the CPU. The computer uses the input/output channels to access secondary storage and transfers the desired data using intermediate area in primary storage. Secondary storage is a non volatile memory. Hard Disks are example of Secondary storage. Some other examples of secondary storage technologies are Flash memory, Floppy disks, magnetic tapes, Optical devises like CD, DVD and also Zip drives.

Storage Devices and Technologies Hard Disk Drive: The most widely used storage device in desktop and Laptop computers is the Hard Disk Drive. The hard disk commonly stores the operating system, application programs and user data. The hard disk drive consists of magnetic coated disks called "platters“ stacked one above other and is written and read by drive heads. Hard Disk Drives are commonly available in 3.5" and 2.5" which denotes the size of the platters. . External disks can be connected using interfaces like SCSI, USB or eSATA. The capacity/price ratio of the hard disk drive is presently rapidly improving which makes it more competitive as a storage medium. The advantages of hard disk drives are low access times, availability, capacity and ease of use

RAID or Disk Array Redundant Array of Independent Disks (RAID) in which the hard disk drives are grouped together using hardware or software and is treated as a single data storage unit. The data is recorded across multiple hard disk drives in parallel, increasing the access time significantly. The array of multiple hard disk drives which forms the RAID can also be partitioned and assigned with a file system.

RAID Functions Striping Mirroring Parity Calculation Striping is the process in which consecutive logical bytes of data is stored per blocks in the consecutive physical disks which forms the array. Mirroring Mirroring is the process in which the data is written to the same block on two or more physical disks in the array. Parity Calculation If there are N number of disks in the RAID array, N-1 consecutive blocks are used for storing data blocks and the Nth block is used for storing the parity When any of the N-1 data blocks are altered, N-2 XOR calculations are performed on the N-1 blocks The Data Blocks and Parity Block is written across the array of hard disk drives that forms the RAID array. If any one of the N blocks fail, the data in that particular block is reconstructed using N-2 XOR calculations on the remaining N-1 blocks If two or more blocks fail in the RAID array the reconstruction of the data from the failed blocks is not possible.

RAID Types RAID 0 RAID 0 is also called as Data Striping with No Parity information. RAID 0 requires a minimum of 2 Hard Disk drives. The advantages of RAID 0 is the increase in performance due to the parallelism in the read and write process. The disadvantage is that there is no redundancy (not a high availability level)

RAID 1 RAID 1 RAID 1 is called as Data Mirroring. RAID 1 requires a minimum of two or more Hard Disk drives. The advantages of RAID 1 are good performance in the read operation as the data is read parallely from several disks. The disadvantage is the slow write process as multiple writes are required. The cost is also doubled.

RAID 0+1 RAID 0+1 RAID 0+1 is a combination of both RAID 0 and RAID 1 in which the data stripping happens on inside and Mirroring happens on the outside.

RAID 1+0 RAID 1+0 RAID 1+0 is a combination of RAID 1 (Mirroring) and RAID 0 (Data Stripping) in which the mirroring is on inside and the data stripping happens on the outside. The advantage of RAID 1+0 is good performance in reads and the improvised write performance when compared to RAID 1.

RAID 1

RAID 4 RAID 4 RAID 4 is a process of independent, whole Block Access in which the data is stored across the number of disks (N-1) and the other disk acts as a dedicated Parity Drive which stores the parity information.

RAID 5 RAID 5 RAID 5 is the process which is identical to the RAID 4, but the parity is striped across multiple drives in the array. RAID 5 requires a minimum of 3 hard disk drives for its configuration. The advantage of RAID 5 is the good read performance due to the parallelism like RAID 0 Cost is slightly increased when compared to the disks without high availability solutions.

Optical Storage Optical Storage is one of the low-cost and reliable storage media used in personal computers for incremental data archiving. Optical storage are available in any one of the three basic formats. They are Compact Disk (CD), Digital versatile disk (DVD) and Blue-ray disk (BD). The media unit costs are very low in Recordable CDs, DVDs and Blue-ray disks. However, when comparing to the hard disk drives or tape drives the capacities and speeds of the optical discs are comparatively lower.

Solid State Drives The solid state drives do not contain any moving parts like the magnetic drives. The solid state drives are also known as flash memory, thumb drives, USB flash drives, Memory Stick, Secure digital cards. The SSDs are relatively expensive when compared to the other types for their low capacity, but are very convenient for backing up the data. SSD drives are presently also available in the order of 500GB to TBs.

Network and Online Storage Network storage is a method in which the user’s data is stored and backed-up onto their company’s network servers. The files stored online are stored in a hard disk drive located remotely to the computer and can be accessed from a remote location. As the internet access is more widespread the remote backup services are gaining popularity. Backing up of users data using the internet to a remote location helps to protect data against worst-case scenarios such as fires, floods, or earthquakes which would destroy any backups stored in the same location.

Objective Understand various storage devices Understand the types of storage systems Understand storage networking technologies Understand storage virtualization

FC-AL (Fibre Channel Arbitrated Loop) FC-AL is a fibre channel topology used to connect devices using a loop topology, is similar to a token ring network. A token is used to prevent data from colliding when two or more streams are sent at the same time. FC-AL passes data using one-way loop technique. FC-AL technology eliminates the expensive fibre channel switches and allows several servers and storage devices to be connected. The fibre channel arbitrated loop can also be called as arbitrated loop. The FC topology has three major fibre channels to connect ports: Switched Fabric : A network topology using crossbar switches that connects devices. Point-to-Point : Allows two-way data communication connecting one device to another. Arbitrated Loop : Devices are connected in a loop, only two devices can communicate at the same time. This is the most common fibre channel used in FC-AL.

FC-AL (Fibre Channel Arbitrated Loop) Fibre channel arbitrated loop can connect upto 127 devices with a port attached to the fabric. In FC-AL only one port can transmit data at a time. FC-AL uses the arbitration signal to choose the port. Once the port is selected by the arbitration signal, it can use the fibre channel, gigabit-speed network topology is used for network storage. The FC-AL topology has the following properties: All devices share the same bandwidth in the loop Can be cabled using hub or loop technology If a port malfunctions in the loop, all ports stop working Two ports function like arbitrated loop and not as a point-to-point 127 ports (devices) can be supported with one port attached to the fabric Has a serial architecture compatible with small computer system interface (SCSI) FC-AL topology is used where interconnection of storage devices is needed and where multiple node connections require high-bandwidth connections.

Types of FC-AL FC-AL are of two types Private loops: Private loops are not connected to the Fabric, so the nodes are inaccessible to the nodes that do not belong to the loop. Public loops: Public loops are connected to the Fabric through one FL Port and are accessible to other nodes that are not part of the loop.

FABRIC Storage Area Network (SAN) Fabric is hardware used to connect workstations and servers to the storage device in a SAN. Fibre Channel switching technology is used in a SAN Fabric to enable any-server to any- storage device connectivity. Fabric is a network topology used to connect network nodes with each other using one or more network switches. Switched Fabric in Fibre Channel: Switched Fabric is a topology in which the devices are connected to each other through one or more Fibre Channel switches. This topology has the best scalability of the three Fibre Channel topologies like Arbitrated loop and Point-to-point as the traffic is spread across multiple physical links and also the only one requiring switches. The visibility among various devices also called as nodes in a fabric is controlled with Zoning.

Methods of implementing zoning There are two methods of implementing zoning Hardware Zoning: Hardware Zoning is a port based zoning method. Physical ports are assigned to a zone. A port can be assigned to one zone or multiple zones at the same time. The devices are connected to a particular port, if the devices are shifted to different port, the entire zone ceases to operate. Software Zoning: Software Zoning is a SNS based zoning method. The device’s physical connectivity to a port does not play a role in the definition of zones. Even if a device is connected to a different port, it remains in the same zone. The hardware zoning is more secure than the software zoning.

Multiple switches in a Fabric Multiple switches in a fabric forms a mesh network with devices on the "edges "of the mesh. Two separate fabrics are found in most Fibre Channel network for redundancy. Both the fabrics share the edge nodes which are unconnected. This setup provides failover, if one link breaks or a fabric goes out of order datagram's can be sent over the second fabric. The number of devices is limited only by the available address spaces in the fabric topology.

Storage Area Network A Storage Area Network (SAN) is a dedicated network that carries data between computer systems and storage devices, which can include tape and disk resources. SAN forms a communication infrastructure providing physical connections and consists of a management layer, which organizes the connections, storage elements, and computer systems so that the data transfer is secure and robust. SAN supports block level operations and does not provide file abstraction. File systems built on SAN’s provide file-level access are called as SAN file systems or shared disk file systems. SAN uses a Fibre Channel Fabric topology specially designed to handle storage communications. The access is faster and more reliable than the protocols used in NAS. A Fibre Channel SAN fabric is made up of a number of Fibre Channel switches. The storage devices can exist in their own separate network and communicate directly with each other over a fast media in an SAN.

Storage Area Network SAN uses different technologies to interconnect different network nodes. Fibre channel is a dedicated high performance channel. It uses the fibre channel protocol. SCSI protocol carries IP packet over the network. Fibre channel can be the source or destination of the information. If the node is the initiator of the information it is connected to the network using HBA (Host Bus Adapter). This is a physical layer connection. If the node is the target for the information then it is connected through RAID or storage drives. Existing communication technologies like optical fibre can also be used by storage area networks. SANs can also support disk mirroring, archival and retrieval of archived data, backup and restore and data migration from one storage device to another and also the sharing of data among various servers. SANs can also contain subnetworks with network-attached storage systems.

Zoning Zoning in a Storage area network is the allocation of resources for the devices load balancing and for allowing access to data only for certain users. Zoning is similar to that of a file system. Zoning can be of two kinds, Hard or Soft zoning. Hard zoning is one in which each device is assigned to a particular zone and this does not change. In the case of soft zoning device assignments can be changed to accommodate variations in demand on different servers in the network. Zoning is used to minimize the risk of data corruption, helps to secure data against hackers and minimizing the spread of viruses and worms. The disadvantage of zoning is the complication in the scaling process if the number of users and servers in a SAN increases significantly.

Storage Virtualization Storage Virtualization is a concept in which the storage system uses virtualization concepts which enables better functionality and advanced features within and across storage systems. Storage virtualization hides the complexity of the SAN by pooling together multiple storage devices to appear as a single storage device. Storage virtualization can be of three types Host based: In the Host based virtualization the virtualization layer is provided by a server and presents a single drive for the applications. The host based storage virtualization depends on the software at the server often at the OS level. Volume Manager is the tool which is used to enable this functionality. The volume manager is configured so that several drives are presented as a single resource which can be divided as needed. Appliance Based: In the Appliance based virtualization a hardware appliance is used which sits on the storage network Network Based: The network based virtualization is similar to the appliance based except that it works at the switching level. Appliance and network based work at the storage infrastructure level. Data can be migrated from one storage unit to another without reconfiguring any of the servers; the virtualization layer handles the remapping.

Storage virtualization Storage virtualization can be implemented using software applications. The main reasons to implement storage virtualization are Improvised storage management in an IT environment Better availability with automated management Better storage utilization Less energy usage Increase in loading and backup speed Cost effective, no need to purchase additional software and hardware

Disadvantages of storage virtualization The common disadvantages of storage virtualization are Storage virtualization uses a network system which is more complicated Failure in any one of the system fails the entire setup The entire network is compromised if any server is infected or breached Storage virtualization can be applied to different storage functions such as physical storage, RAID arrays, LUNs, storage zones and logical volumes.

Virtualization The two main types of virtualization are: Block Virtualization: The abstraction (separation) of logical storage (partition) from the physical storage so that the partition can be accessed without regard to the physical storage. The separation of the logical storage from the physical storage allows greater flexibility to manage storage for the users. File Virtualization: File virtualization eliminates the dependencies between the data accessed at the file level and the physical location where the files are stored. This optimizes the storage use and server consolidation and also to perform non-disruptive file migrations.