Storage Technology and Management W.lilakiatsakun

Storage Technology JBOD (Just Bunch Of Disk) JBOD (Just Bunch Of Disk) RAID (Redundant arrays of inexpensive disks) RAID (Redundant arrays of inexpensive disks) SSA (Serial Storage Architecture) SSA (Serial Storage Architecture)

JBOD (Just Bunch Of Disk) (1)

JBOD (Just Bunch Of Disk) (2) JBOD can be used as individual disks or any RAID configuration or Concatenation (SPAN) depending on the Host Bus Adapter JBOD can be used as individual disks or any RAID configuration or Concatenation (SPAN) depending on the Host Bus AdapterHost Bus AdapterHost Bus Adapter Concatenation or Spanning of disks is a popular method for combining multiple physical disk drives into a single virtual disk. Concatenation or Spanning of disks is a popular method for combining multiple physical disk drives into a single virtual disk. – It provides no data redundancy. – Disks are merely concatenated together so they appear to be a single large disk. concatenated

JBOD (Just Bunch Of Disk) (3) For example, JBOD (Just a Bunch Of Disks) could combine 3 GB, 15 GB, 5.5 GB, and 12 GB drives into a logical drive at 35.5 GB, which is often more useful than the individual drives separately. For example, JBOD (Just a Bunch Of Disks) could combine 3 GB, 15 GB, 5.5 GB, and 12 GB drives into a logical drive at 35.5 GB, which is often more useful than the individual drives separately.

Redundant arrays of inexpensive disks (RAID) The organization distributes the data across multiple smaller disks, offering protection from a crash that could wipe out all data on a single, shared disk. The organization distributes the data across multiple smaller disks, offering protection from a crash that could wipe out all data on a single, shared disk. Benefits are depended on level of RAID Benefits are depended on level of RAID

RAID0 (stripe set or striped volume) RAID Level 0 splits data evenly across two or more disks (striped) with no parity information for redundancy. RAID Level 0 splits data evenly across two or more disks (striped) with no parity information for redundancy. It is important to note that RAID 0 provides zero data redundancy. It is important to note that RAID 0 provides zero data redundancy. RAID 0 is normally used to increase performance RAID 0 is normally used to increase performance A RAID0 can be created with disks of differing sizes, but the storage space added to the array by each disk is limited to the size of the smallest disk A RAID0 can be created with disks of differing sizes, but the storage space added to the array by each disk is limited to the size of the smallest disk

RAID0 – Summary (1) RAID 0 uses a very simple design and is easy to implement with a HUGE performance advantage. RAID 0 uses a very simple design and is easy to implement with a HUGE performance advantage. I/O performance is greatly improved by spreading the I/O load across many channels and drives while the best performance is achieved when data is striped across multiple controllers with only one drive per controller. I/O performance is greatly improved by spreading the I/O load across many channels and drives while the best performance is achieved when data is striped across multiple controllers with only one drive per controller.

RAID0 – Summary (2) No parity calculation overhead is involved No parity calculation overhead is involved Not a "True" RAID because it is NOT fault- tolerant. Not a "True" RAID because it is NOT fault- tolerant. The failure of just one drive will result in all data in an array being lost. The failure of just one drive will result in all data in an array being lost.

RAID1 (mirrorring) A RAID 1 creates an exact copy of a set of data on two or more disks. A RAID 1 creates an exact copy of a set of data on two or more disks. This is useful when read performance or reliability are more important than data storage capacity. This is useful when read performance or reliability are more important than data storage capacity. Such an array can only be as big as the smallest member disk. Such an array can only be as big as the smallest member disk. A classic RAID 1 mirrored pair contains two disks which increases reliability A classic RAID 1 mirrored pair contains two disks which increases reliability

RAID1 – Summary (1) RAID Level 1 requires a minimum of 2 drives to implement. RAID Level 1 requires a minimum of 2 drives to implement. 100 redundancy of data means no rebuild is necessary in case of a disk failure, just a copy to the replacement disk. 100 redundancy of data means no rebuild is necessary in case of a disk failure, just a copy to the replacement disk. Transfer rate per block is equal to that of a single disk. Transfer rate per block is equal to that of a single disk. Simplest RAID storage subsystem design. Simplest RAID storage subsystem design.

RAID1 – Summary (2) Highest disk overhead of all RAID types - inefficient due to the duplication of Write tasks. Highest disk overhead of all RAID types - inefficient due to the duplication of Write tasks. Typically the RAID function is done by system software, loading the CPU/Server and possibly degrading throughput at high activity levels. Typically the RAID function is done by system software, loading the CPU/Server and possibly degrading throughput at high activity levels. Hardware implementation is strongly recommended. Hardware implementation is strongly recommended. –May not support hot swap of failed disk when implemented in "software".

RAID 0 +1 (A Mirror of Stripes) RAID Level 0+1 is implemented as a mirrored array whose segments are RAID 0 arrays. RAID Level 0+1 is implemented as a mirrored array whose segments are RAID 0 arrays. RAID Level 0+1 requires a minimum of 4 drives to implement RAID Level 0+1 requires a minimum of 4 drives to implement

RAID 10 (A Stripe of Mirrors) RAID 10 is implemented as a striped array whose segments are RAID 1 arrays. RAID 10 is implemented as a striped array whose segments are RAID 1 arrays. RAID Level 10 requires a minimum of 4 drives to implement. RAID Level 10 requires a minimum of 4 drives to implement.

RAID3 (Parallel access with a dedicated parity disk) RAID Level 3uses byte-level striping with a dedicated parity disk. RAID Level 3uses byte-level striping with a dedicated parity disk. This comes about because any single block of data will be spread across all members of the set and will reside in the same location. This comes about because any single block of data will be spread across all members of the set and will reside in the same location. So, any I/O operation requires activity on every disk. So, any I/O operation requires activity on every disk.

RAID3 – Summary Level 3 only requires one dedicated disk in the array to hold parity information. Level 3 only requires one dedicated disk in the array to hold parity information. The server's data is then striped across the remaining drives, usually one byte at a time. The server's data is then striped across the remaining drives, usually one byte at a time. The parity drive then keeps track of all the info on the striped drive(s) and uses it to restore info if the drive should fail. The parity drive then keeps track of all the info on the striped drive(s) and uses it to restore info if the drive should fail. Because of the parity information that is stored and because Write operations take place on a byte level, Read/Write operations often take longer than other RAID configurations. Because of the parity information that is stored and because Write operations take place on a byte level, Read/Write operations often take longer than other RAID configurations.

RAID5 (Independent access with distributed parity) A RAID 5 uses block-level striping with parity data distributed across all member disks. A RAID 5 uses block-level striping with parity data distributed across all member disks. A minimum of 3 disks is generally required for a complete RAID 5 configuration. A minimum of 3 disks is generally required for a complete RAID 5 configuration. In the example, a read request for block "A1" would be serviced by disk 0. In the example, a read request for block "A1" would be serviced by disk 0. A simultaneous read request for block B1 would have to wait, but a read request for B2 could be serviced concurrently by disk 1 A simultaneous read request for block B1 would have to wait, but a read request for B2 could be serviced concurrently by disk 1

RAID 5 – Summary Level 5 also relies on parity information to provide redundancy and fault tolerance using independent data disks with distributed parity blocks. Level 5 also relies on parity information to provide redundancy and fault tolerance using independent data disks with distributed parity blocks. Each entire data block is written onto a data disk; parity for blocks in the same rank is generated on Writes, recorded in a distributed location and checked on Reads. Compared to RAID 3, RAID 5 uses striping to spread parity information across multiple drives. Each entire data block is written onto a data disk; parity for blocks in the same rank is generated on Writes, recorded in a distributed location and checked on Reads. Compared to RAID 3, RAID 5 uses striping to spread parity information across multiple drives. Requirements: RAID Level 5 requires a minimum of 3 drives to implement. Requirements: RAID Level 5 requires a minimum of 3 drives to implement.

SSA (Serial Storage Architecture) (1) Serial Storage Architecture (SSA) defines a high- performance serial link for the attachment of input/output devices. Serial Storage Architecture (SSA) defines a high- performance serial link for the attachment of input/output devices. –It has been optimized for storage applications such as hard disk drives, host adapter cards, and array controllers. SSA has many advantages over existing parallel interfaces such as the Small Computer Systems Interface (SCSI-2). SSA has many advantages over existing parallel interfaces such as the Small Computer Systems Interface (SCSI-2). –It uses compact cables and connectors, and it has better performance, connectivity, and reliability.

SSA (Serial Storage Architecture) (2) Disk Subsystem provide a peak data rate of 20 MB/s in each direction. Disk Subsystem provide a peak data rate of 20 MB/s in each direction. However, a typical loop configuration with one host adapter can provide a total sustained bandwidth of up to 80 MB/s, and higher speeds are becoming available. However, a typical loop configuration with one host adapter can provide a total sustained bandwidth of up to 80 MB/s, and higher speeds are becoming available. The physical medium is usually a copper cable up to 20 meters long, but fiber optics can also be used for longer distances. The physical medium is usually a copper cable up to 20 meters long, but fiber optics can also be used for longer distances.

SSA (Serial Storage Architecture) (3)

SSA (Serial Storage Architecture) (4) Architecture overview Architecture overview SSA is defined in three layers: SSA is defined in three layers: SSA-PH1 defines the electrical specifications, cables, and connectors. SSA-PH1 defines the electrical specifications, cables, and connectors. SSA-TL1 is a general-purpose transport layer. It defines the transmission protocol, configuration, and error recovery. SSA-TL1 is a general-purpose transport layer. It defines the transmission protocol, configuration, and error recovery. SSA-S2P is a mapping of the SCSI-2 queuing model, command set, status, and sense bytes. SSA-S2P is a mapping of the SCSI-2 queuing model, command set, status, and sense bytes.

Storage Model

Storage Area Network A SAN is a specialized, high-speed network attaching servers and storage devices A SAN is a specialized, high-speed network attaching servers and storage devices It is sometimes referred to as “the network behind the servers.” It is sometimes referred to as “the network behind the servers.” A SAN introduces the flexibility of networking to enable one server or many heterogeneous servers to share a common storage utility, which may comprise many storage devices, including disk, tape, and optical storage. A SAN introduces the flexibility of networking to enable one server or many heterogeneous servers to share a common storage utility, which may comprise many storage devices, including disk, tape, and optical storage.

SAN Component SAN Connectivity SAN Connectivity –the connectivity of storage and server components typically using Fibre Channel (FC). SAN Storage SAN Storage –TAPE /RAID /JBOD (Just Bunch of Disk) /SSA (Serial Storage Architecture) SAN Server SAN Server –Windows /Unix /Linux and etc

Switched Fabric An infrastructure specially designed to handle storage communications called a fabric. An infrastructure specially designed to handle storage communications called a fabric.fabric A typical Fibre Channel SAN fabric is made up of a number of Fibre Channel switches. A typical Fibre Channel SAN fabric is made up of a number of Fibre Channel switches.Fibre Channel switchesFibre Channel switches Today, all major SAN equipment vendors also offer some form of Fibre Channel routing solution, and these bring substantial scalability benefits to the SAN architecture by allowing data to cross between different fabrics without merging them. Today, all major SAN equipment vendors also offer some form of Fibre Channel routing solution, and these bring substantial scalability benefits to the SAN architecture by allowing data to cross between different fabrics without merging them.

Fiber Channel protocol (1) FC0 The physical layer, which includes cables, fiber optics, connectors, pinouts etc. FC0 The physical layer, which includes cables, fiber optics, connectors, pinouts etc.connectors, pinoutsconnectors, pinouts FC1 The data link layer, which implements the 8b/10b encoding and decoding of signals. FC1 The data link layer, which implements the 8b/10b encoding and decoding of signals.8b/10b FC2 The network layer, defined by the FC2 The network layer, defined by the FC-PI-2 standard, consists of the core of Fibre Channel, and defines the main protocols.

Fiber Channel protocol (2) FC3 The common services layer, a thin layer that could eventually implement functions like encryption or RAID. FC3 The common services layer, a thin layer that could eventually implement functions like encryption or RAID. FC4 The Protocol Mapping layer. Layer in which other protocols, such as SCSI, are encapsulated into an information unit for delivery to FC2. FC4 The Protocol Mapping layer. Layer in which other protocols, such as SCSI, are encapsulated into an information unit for delivery to FC2.

Storage Management Monitoring disk use Monitoring disk use –Disk monitor agent scans the server volumes to collect disk use information Hierarchical storage management Hierarchical storage management –Files will be archived according to certain criteria Prevention against Data Loss Prevention against Data Loss –To protect and recovery from loss Outsourcing storage management Outsourcing storage management

Monitoring disk use One or more the following categories of information can be collected One or more the following categories of information can be collected –Volumes:(Disk) total space : used /available –Directories: what are there –Directory and File owners: who create / who use /when create

Hierarchical storage management When disk space becomes exhausted, data files need to be backup (as archived file or back up tape) When disk space becomes exhausted, data files need to be backup (as archived file or back up tape) –Software tools (Back up tools) When a file system reaches a predefined threshold of X percent full When a file system reaches a predefined threshold of X percent full –automated procedure are initiated that determine which files are eligible for archive and are currently backed up –The file catalog is then updated to indicate that files have been archived and deletes them from the disk file system

Prevention against data loss (1/2) Data perspective Data perspective –Backups sent off-site in regular intervals –Use a Remote backup facility if possible to minimize data loss –Storage Area Networks (SANs) over multiple sites make data immediately available without the need to recover or synchronize it

Prevention against data loss (2/2) Facility perspective Facility perspective –Surge Protectors — to minimize the effect of power surges on delicate electronic equipment –Uninterruptible Power Supply (UPS) and/or Backup Generator –Fire Preventions — more alarms, accessible extinguishers –Anti-virus software and other security measures

Techniques to prevent data loss Mirroring Mirroring –Disk mirroring : Redundant arrays of inexpensive disks 1 (RAID1) –Server mirroring: web / ftp / On-site data storage On-site data storage –Back up - Tape / optical disk Off-site data storage (backup-site) Off-site data storage (backup-site) –Cold sites –Warm sites –Hot site

Mirroring Mirroring can occur locally or remotely. Mirroring can occur locally or remotely. –Locally means that a server has a second hard drive that stores data. –A remote mirror means that a remote server contains an exact duplicate of the data. Data is written to the original drive when a write request is issued and then copied to the mirrored drive, providing a mirror image of the primary drive. Data is written to the original drive when a write request is issued and then copied to the mirrored drive, providing a mirror image of the primary drive.

Disk mirroring (RAID1) The replication of logical disk volumes onto separate physical hard disks in real time to ensure continuous availability, currency and accuracy. The replication of logical disk volumes onto separate physical hard disks in real time to ensure continuous availability, currency and accuracy. A mirrored volume is a complete logical representation of separate volume copies A mirrored volume is a complete logical representation of separate volume copies

Server mirroring Mirror sites are most commonly used to provide multiple sources of the same information, and are of particular value as a way of providing reliable access to large downloads. Mirror sites are most commonly used to provide multiple sources of the same information, and are of particular value as a way of providing reliable access to large downloads. Web server Web server –To preserve a website or page, especially when it is closed or is about to be closed –Load balancing server server –To protect loss of information ftp server ftp server –To allow faster downloads for users at a specific geographical location –Load balancing

Back up site A backup site is a location where a business can easily relocate following a disaster, such as fire, flood, or terrorist threat. This is an integral part of the disaster recovery plan of a business. A backup site is a location where a business can easily relocate following a disaster, such as fire, flood, or terrorist threat. This is an integral part of the disaster recovery plan of a business.fire floodterroristdisaster recovery planbusinessfire floodterroristdisaster recovery planbusiness A backup site can be another location operated by the business, or contracted via a company that specializes in disaster recovery services. A backup site can be another location operated by the business, or contracted via a company that specializes in disaster recovery services. In some cases, a business will have an agreement with a second business to operate a joint disaster recovery facility. In some cases, a business will have an agreement with a second business to operate a joint disaster recovery facility.

Cold Sites A cold site is the most inexpensive type of backup site for a business to operate. A cold site is the most inexpensive type of backup site for a business to operate. It provides office spaces to operate It provides office spaces to operate It does not include backed up copies of data and information from the original location of the business, nor does it include hardware already set up. It does not include backed up copies of data and information from the original location of the business, nor does it include hardware already set up. The lack of hardware contributes to the minimal startup costs of the cold site, but requires additional time following the disaster to have the operation running at a capacity close to that prior to the disaster. The lack of hardware contributes to the minimal startup costs of the cold site, but requires additional time following the disaster to have the operation running at a capacity close to that prior to the disaster.

Warm Sites A warm site is a location where the business can relocate to after the disaster that is already stocked with computer hardware similar to that of the original site, but does not contain backed up copies of data and information. A warm site is a location where the business can relocate to after the disaster that is already stocked with computer hardware similar to that of the original site, but does not contain backed up copies of data and information.

Hot Sites A hot site is a duplicate of the original site of the business, with full computer systems as well as near- complete backups of user data. A hot site is a duplicate of the original site of the business, with full computer systems as well as near- complete backups of user data. Ideally, a hot site will be up and running within a matter of hours. This type of backup site is the most expensive to operate. Ideally, a hot site will be up and running within a matter of hours. This type of backup site is the most expensive to operate. Hot sites are popular with stock exchanges and other financial institutions who may need to evacuate due to potential bomb threats and must resume normal operations as soon as possible. Hot sites are popular with stock exchanges and other financial institutions who may need to evacuate due to potential bomb threats and must resume normal operations as soon as possible.stock exchanges financial institutionsbomb threatsstock exchanges financial institutionsbomb threats

How to choose (1) Choosing the type is mainly decided by a company's cost vs. benefit strategy. Choosing the type is mainly decided by a company's cost vs. benefit strategy. Hot sites are traditionally more expensive than cold sites since much of the equipment the company needs has already been purchased and thus the operational costs are higher. Hot sites are traditionally more expensive than cold sites since much of the equipment the company needs has already been purchased and thus the operational costs are higher. However if the same company loses a substantial amount of revenue for each day they are inactive then it may be worth the cost. However if the same company loses a substantial amount of revenue for each day they are inactive then it may be worth the cost.

How to choose (2) The advantages of a cold site are simple--cost. It requires much fewer resources to operate a cold site because no equipment has been bought prior to the disaster. The advantages of a cold site are simple--cost. It requires much fewer resources to operate a cold site because no equipment has been bought prior to the disaster. The downside with a cold site is the potential cost that must be incurred in order to make the cold site effective. The downside with a cold site is the potential cost that must be incurred in order to make the cold site effective. The costs of purchasing equipment on very short notice may be higher and the disaster may make the equipment difficult to obtain. The costs of purchasing equipment on very short notice may be higher and the disaster may make the equipment difficult to obtain.