Appendix A: Introduction to Serial Attached SCSI
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71
How are Disk Drives Identified in SAS?
In the BIOS and in the management utilities (see
Identifying Disk Drives
on page 90
), disk
drives are identified in the following formats:
●
CNX:DevY = Device Y is attached to Connector X (see
Direct-attach Connections
below for
more information)
●
BoxX:SlotX = Enclosure X is attached to a disk drive in Slot X (see
Backplane Connections
below for more information)
●
ExpX:PhyX = Expander X is attached to Phy X (see
SAS Expander Connections
below for
more information)
where X is the count number.
Note:
Devices other than disk drives (CDROM, tape drives, etc...) are listed in order after your
system disk drives.
In parallel SCSI, XX is the disk drive’s channel number, YY is the target number, and ZZ is the
logical unit number (LUN).
What are the SAS Connection Options?
You can connect end devices to each other through direct cable connections and through
backplane connections. When you use one or more expander devices (see
page 72
), you can
create large configurations.
Direct-attach Connections
In a direct-attach connection, SAS or SATA disk drives are connected directly to a SAS card
with SAS or mini-SAS cables. One disk drive is attached to one SAS/mini-SAS connector with
one SAS/mini-SAS cable (or multiple disk drives are attached to one SAS/mini-SAS connector
with one fan-out cable). The figure on
page 39
shows an example of direct-attach connections.
The number of direct-attached disk drives is limited to the number of
phys
supported by the
SAS card. (Note that there may be multiple phys within a single connector. See
page 72
.)
Backplane Connections
In a backplane connection, disk drives and SAS cards are attached to and communicate with
each other through a system backplane.
There are two types of backplane connections,
passive
and
active
. When connecting to either
backplane, it’s important to properly connect your disk drive LEDs in order to identify disk
drive conditions. See
About Your RAID Controller
on page 15
for your RAID controller Activity
LED connections and locations.
When connecting to a backplane, the ICP Storage Manager enables you to manage your system
disk drives, see
Monitoring Disk Drives with ICP Storage Manager
on page 41
.
The number of end devices is limited to the number of slots available on the backplane. For
example, the Adaptec S50 enclosure, which contains an expander, is a backplane connection
that supports up to 12 SAS or SATA disk drives.