Dot Hill Systems SANnet II 200 - Manual (Page 34)

34
devices and servers providing accelerated data access.
SCA Single connector attachment. A SCSI disk connector technology coinvented by Sun
Microsystems. The SCA provides all SCSI, power, and control signals in a single
connector, and enables easy servicing and highly reliable, pluggable disk drives.
SCSI Small Computer Systems Interface. An industry standard for connecting disk and tape
devices to a workstation.
SCSI address The octal representation of the unique address (0-7) assigned to a narrow device; or hex
representation of the unique address (0-15) assigned to a wide SCSI device.
SES SCSI Enclosure Services driver. An interface to SCSI Enclosure Services devices. These
devices sense and monitor the physical conditions within an enclosure, as well as enable
access to the status reporting and configuration features of the enclosure (such as indicator
LEDs on the enclosure).
SID Primary controller identifier number
simplex Transmission in one preassigned direction only. See also full-duplex and half-duplex.
SMTP Simple Mail Transfer Protocol. A protocol for sending e-mail messages between servers
and from mail clients to mail servers. The messages can then be retrieved with an e-mail
client using either POP or IMAP.
SNMP Simple Network Management Protocol. A set of protocols for managing complex
networks. SNMP works by sending messages, called protocol data units (PDUs), to
different parts of a network. SNMP-compliant devices, called agents, store data about
themselves in Management Information Bases (MIBs) and return this data to the SNMP
requesters.
spanning Disk spanning makes use of the firmware's striping capability to stripe data across two
otherwise independent RAID logical drives. The two spanned logical drives are presented
to the operating environment as one logical drive. The advantages of spanning are: --
Supports two simultaneous drive failures in the combined fault tolerant logical drives
(provided there is one drive failure from each logical drive). -- Improves performance
because the number of spindles is increased. The disadvantage of spanning is that the
RAID overhead for redundant RAID levels is increased since each logical drive handles
fault tolerance separately.
split channel Inside the same drive array enclosure, when the drive channel is evenly divided into two
separate channels; for example, when a 12-drive channel is cleaved into two independent
channels
standby drive A drive that is marked as a spare to support automatic data rebuilding after a physical
drive associated with a logical drive fails. For a standby drive to take the place of another
drive, it must be at least equal in size to the failed drive and all of the logical drives
dependent on the failed disk must be redundant.
state The current operational status of a disk drive, a logical drive, or redundant controllers. The
array stores the states of drives, logical drives, and redundant controllers in its nonvolatile
memory. This information is retained across array power interruptions.
stripe sizestriping This is the amount of data in kilobytes that is striped across each physical drive in a
logical drive. The values are in increments of 8 kilobytes and range from 8 to 64 kilobytes.
Generally, large stripe sizes are more effective for arrays with primarily sequential reads.
To change the stripe size on an existing drive, you need to back up your data, redefine the
stripe size, reconfigure the storage, and restore all the data. The storing of sequential
blocks of incoming data on all the different SCSI drives in a logical drive. For example, if
there are three SCSI drives in a logical drive, data will be stored as follows: block 1 on
SCSI drive 1; block 2 on SCSI drive 2; block 3 on SCSI drive 3; block 4 on SCSI drive 1;
block 5 on SCSI drive 2, etc. This method of writing data increases the disk array
throughput because multiple drives are working simultaneously, retrieving and storing.
RAID 0, 3, 5 or 1+ 0 all use striping.
striping Spreading, or interleaving, logically contiguous blocks of data across multiple
i d
d t di k i dl Th t f d t itt h di k b f i t th