access control record
Controls host access to a volume and its snapshots. Access can be restricted through IP address, iSCSI initiator name, or CHAP user name.
active control module
In a dual control module array, the control module that is actively serving I/O. To physically identify the active control module, examine the array front panel. The LED labeled ACT will be green on the active control module.
array
A PS Series array is a completely self-contained storage unit that includes at least seven and up to fourteen disks in a highly-available disk array with single or dual control modules and redundant power supplies and fan modules.
bandwidth
Rate at which an I/O subsystem or component can transfer bytes of data. Also, sometimes called the transfer rate.
CHAP
Acronym for Challenge Handshake Authentication Protocol, used in conjunction with access control records to restrict host access to volumes and snapshots. CHAP is a network login protocol that uses a challenge-response mechanism. With CHAP authentication, volume and snapshot access can be restricted to hosts that supply the correct account name and password combination.
CLI
Acronym for Command Line Interface, used to manage groups and arrays. CLI commands can be used in scripts.
cloning
Functionality that enables the creation of an exact copy of a volume or a copy of a volume as it existed at the time a snapshot or replica was created.
One or more snapshots created at the same time through a multi-volume snapshot operation.
default gateway
Local router that is used to forward network traffic beyond the local network.
Converts a replicated volume to a failback replica set for the purpose of failing back data from the secondary group, or converts a recovery volume to an inbound replica set, returning it to its original state. Also, see promote and failback.
discovery
Discovery, or auto-discovery, involves an iSCSI initiator requesting from a target portal a list of valid iSCSI targets (for example, volumes or snapshots) and making those targets available for use by the initiator.
Mechanism for temporarily hosting a volume on the secondary group and then returning to the primary group. You may want to use failback if the primary group is unavailable due to failure or maintenance.
To perform failback, you can promote the volume’s inbound replica set to a recovery volume (allowing initiators to access the recovery volume, as needed), demote the original volume (when it becomes available) to a failback replica set, replicate volume changes to synchronize the groups, demote the recovery volume to the original inbound replica set, and then promote the failback replica set to the original volume.
When configuring a volume for replication, if you enable the option to retain the failback snapshot, you may be able to fail back to the primary group by replicating only the changes that occurred while the volume was hosted on the secondary group.
Indicates the point at which you may be able to fail back to the primary group by replicating only the changes that occurred while the volume was hosted on the secondary group. A failback baseline depends on the existence of a failback snapshot. See failback and failback snapshot.
failback replica set
Replica set created by demoting a replicated volume. To return to the original volume, you must promote the failback replica set. See failback, demote, and promote.
Snapshot that represents the most recent complete replica and establishes the failback baseline. When configuring a volume for replication, if you enable the option to retain the failback snapshot, you may be able to fail back to the primary group by replicating only the changes that occurred while the volume was hosted on the secondary group. See failback baseline.
Gigabit Ethernet
Group of Ethernet standards in which data is transmitted at a rate of one Gigabit per second.
group
See PS Series group.
A user who has permission to manage all features and objects in a PS Series group, including configuring replication partners. Compare to pool administrator.
group IP address
Highly available IP address that is used by iSCSI initiators and administrators to access a group.
group member
See member.
host
Any computer directly connected to a network that acts as a repository for services (such as e-mail or FTP) available to other computers on the network.
host bus adapter
I/O adapter that links an iSCSI initiator with target systems.
hot-swapping
Removing a component from a PS Series array and installing a replacement while the power is on, the array is running, and without disrupting I/O.
iSCSI
Acronym for Internet Small Computer Systems Interface. Standard protocol for transporting storage I/O block data over an IP network.
Hardware or software that starts the transfer of information to and/or from an iSCSI target (for example, a volume or snapshot).
SCSI block storage device that is accessed through TCP/IP and iSCSI protocols. Each volume and snapshot is seen on the network as an iSCSI target.
iSNS
Acronym for Internet Storage Name Service. Facilitates the automated discovery, management, and configuration of iSCSI and other devices on a TCP/IP network.
latency
Amount of time needed to complete a specific I/O operation. Also called delay.
manual transfer replication
The process of sending the first replica of a volume (the entire volume contents) to the partner location using physical media such as a CD-ROM, instead of the network. Used in cases where the network link between replication partners is too slow or otherwise unsuitable for transferring large amounts of data. Manual transfer replication applies only to the first data transfer for a volume.
Manual Transfer Utility
A stand-alone utility that enables you to perform the first volume replication using external media, instead of the network. The utility has two versions, a graphical user interface and an interactive command line interface.
A PS Series array that is connected to the network and has been configured into a PS Series group. Groups can have several members, optionally configured into one or more storage pools.
MIB
Acronym for Management Information Base (or Bases, when written as MIBs). A type of database used to manage the devices in a communications network. SNMP, a communication protocol between management stations (consoles, for example) and managed objects (such as routers, gateways, and switches) makes use of MIBs.
Writing and maintaining the same (redundant) data in two equal-sized segments residing on two separate disks to protect data against loss due to disk or device I/O failure.
MRTG
Acronym for Multi Router Traffic Grapher, a third-party utility to monitor group performance.
multi-subnet configuration
Network configuration in which some of the IP addresses assigned to the network interfaces on the members and the group IP address reside on different subnets.
netmask
Network address used to identify the network segment (subnet) on which an IP address (network interface) resides. Same as subnet mask.
notification
Method a group uses to automatically inform users of significant events through e-mail, remote syslog files, and SNMP traps.
NTP
Acronym for Network Time Protocol. Defines a set of procedures for synchronizing clocks on hosts connected to a network and having access to the Internet.
parity
Form of redundancy used to re-create the data on a failed disk.
Portion of group disk space to which you assign members and volumes. Pools provide you with greater control of group storage space and enable you to segregate users and applications, while maintaining a single-system view of the storage. Also called storage pool.
A user who has permission to manage objects only in a specific pool or set of pools for a group. Compare to group administrator.
primary volume
A volume configured for replication to a partner group.
Converts an inbound replica set to a temporary recovery volume or converts a failback replica set to a volume, returning it to its original state. An inbound replica set can also be promoted to a volume that cannot be demoted (a permanent promotion). Also, see demote and failback.
One or more PS Series arrays (members) configured on a network, accessed through a single IP address, and managed as a single system.
RADIUS
Acronym for Remote Authentication Dial-in User Service. This service centralizes the authentication and management (and optionally accounting) of user accounts and login information for multiple network connections.
RAID policy
The combined RAID level (RAID 10, RAID 5, or RAID 50) and spare disk policy for a member.
RAID
Acronym for Redundant Array of Independent Disks. The disks are joined together and managed as a single element. RAID arrays set aside part of the physical storage capacity to store redundant information about the data stored on the array. This information can then be used to regenerate user data in the event a disk in the array fails or the access to the disk fails.
RAID 0 (striping)
RAID level that distributes (stripes) data evenly across disks in equal-sized segments. Striping improves performance but does not provide fault tolerance.
RAID 1 (mirroring)
RAID level in which data is mirrored across (written to) two disk drives for redundancy and high availability.
RAID 5 (distributed parity)
RAID level in which parity information is distributed across all drives in the array for redundancy and high availability.
RAID 10
RAID level consisting of striping on top of multiple RAID 1 sets. Also called performance optimization.
RAID 50
RAID level consisting of striping on top of two RAID 5 sets. Also called capacity optimization.
primary group
In a replication operation, the group where the base (or primary) volume resides. See secondary group.
recovery group
In a replication operation, the group (also called the secondary group) where volume data can be recovered if the primary group where the original volume resides is destroyed.
recovery volume
Temporary volume created by promoting an inbound replica set. To return to the original inbound replica set, you must demote the recovery volume. See demote, failback, and promote.
replica
Represents the contents of a volume at a specific point in time, located on the secondary group in the replication operation. You can clone a replica or promote a replica set to recover volume data.
replica set
Set of complete replicas for a volume. You can promote a replica set to recover volume data.
replication
Functionality that enables you to replicate (copy) volumes from the primary group, where the volume resides, to the secondary group, where volume data can be recovered in the event of a disaster. The groups can be separated by an unlimited distance.
replica collection
One or more replicas created at the same time from a volume collection, containing one replica for each volume in the collection.
replica collection set
The set of replica collections for a volume collection.
Volume size as seen by iSCSI initiators. For a volume without thin provisioning enabled, the entire amount of space indicated by the reported size is allocated to the volume (that is, the reported size is the same as the volume reserve). For a volume with thin provisioning enabled, only the volume reserve is allocated to the volume. Therefore, the reported size may differ from the volume reserve, which increases as the thin-provisioned volume becomes in use. See volume reserve.
SAN
Acronym for Storage Area Network, a high-speed subnetwork of shared storage devices. SAN architecture enables you to consolidate storage and simplify storage management. As more storage devices are added to a SAN, they too will be accessible from any server in the larger network. PS Series groups are iSCSI SANs, in which storage devices are accessible from an Ethernet network.
SAS
Acronym for Serial Attached SCSI technology. SAS is a serial communication protocol for direct attached storage (DAS) devices.
SATA
Acronym for Serial ATA (Advanced Technology Attachment) technology. SATA is the successor to the legacy ATA standard.
SCSI
Acronym for Small Computer System Interface.
secondary control module
In a dual control module array, the control module that mirrors data from the active control module.
In a replication operation, the group (also called the recovery group) where the replicas are stored. Volume data can be recovered on the secondary group if the primary group, where the original volume resides, is destroyed.
SES
Acronym for SCSI Enclosure Services. A SCSI command set is defined for managing various non-SCSI elements contained within the enclosure.
single-subnet configuration
Network configuration in which the group IP address and the IP addresses assigned to the group member network interfaces reside on the same subnet.
SMART
Acronym for Self-Monitoring Analysis and Reporting Technology. This technology is designed to determine the reliability status of a disk. If the SMART system determines that a failure is imminent, the member would fail the disk and notify the user.
SMTP
Acronym for Simple Mail Transfer Protocol. SMTP is the protocol used for routing e-mail across the Internet.
snapshot
Represents the contents of a volume at a specific point in time and is seen on the network as an iSCSI target. Can be used for backups, testing, and upgrades. To recover data, you can restore a volume from a snapshot or clone a snapshot.
snapshot collection
One or more snapshots created at the same time from a volume collection or through a multi-volume snapshot operation. See custom snapshot collection.
SNMP
Acronym for Simple Network Management Protocol.
spare (disk)
PS Series array disk used as a hot standby (redundant) component. A spare disk is powered on but does not operate until a data disk fails. Spare disks are configured and used automatically.
SSH
Acronym for Secure Shell, a program developed to log into another computer over a network, to execute commands in a remote machine, and to move files from one machine to another. It provides strong authentication and secure communications over insecure channels.
SSL
Acronym for Secure Socket Layer, a protocol developed by Netscape for transmitting private documents via the Internet. SSL works by using a public key to encrypt data that is transferred over the SSL connection. Many websites use SSL to obtain confidential user information, such as credit card numbers. By convention, URLs that require an SSL connection start with https: instead of http:.
storage pool
See pool.
subnet mask
Network address used to identify the network segment (subnet) on which an IP address (network interface) resides. Same as netmask.
target portal
A target or iSCSI portal is the IP and TCP port number pair for a target. The default port number is 3260.
Feature that allows administrators to improve storage resource utilization by logically over-allocating SAN volumes. With thin provisioning, you can meet current and future storage capacity needs while eliminating the difficulty of adding storage to applications or operating systems that do not support online expansion.
When first created, the volume reserve for a thin-provisioned volume is only a portion of the volume size. As the volume is used, the volume reserve will grow, up to a user-defined limit, at which point the volume is set offline. A warning is issued as additional space is allocated, enabling you to make adjustments, if desired.
throughput
Rate at which an I/O subsystem or component can perform I/O operations.
vacate
Operation in which all the volume data on a member is moved to a different member. For example, a member vacate operation occurs when you remove a member from the group or move a member across storage pools.
volume
Logical device representing a portion of storage pool space and seen on the network as an iSCSI target. Volume data is distributed across the pool members. Volumes are protected with access control records and can be expanded and load-balanced without disrupting access to the volume.
volume collection
One or more volumes grouped together for the purposes of creating snapshots or replicas at the same time.
Amount of pool space allocated to a volume (consumed from free pool space). For a volume without thin provisioning enabled, the volume reserve is the same as the reported size (seen by initiators). For a thin-provisioned volume, the volume reserve is initially set to a minimum value and then increases automatically (if space is available) as the volume becomes in use. See reported size and thin provisioning.