Dell PowerVault 221S (SCSI) - Manual (Page 23)

A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02
PAGE 23 11/17/2005
be reserved for use by the second SCSI controller. A mapping of the SCSI ID address
space reserved by the PV22xS enclosure is shown in Figure 4-5.
The HDD identifiers are
directly mapped to it’s assigned SCSI ID, as shown in Figure 4-6 .
Figure 4-5 SCSI ID Assignments
Figure 4-6 SCSI ID Numbers and Associated Hard Disk Drives
Multiple PV22xS Enclosures on a Single Host System
Daisy chaining of Multiple PV22xS enclosures is not supported. This is due to SCSI
limitation of only allowing a maximum of 16 devices on one SCSI bus. Daisy chaining
would effectively concatenate the devices in two (or more) enclosures into a single SCSI
bus, thus violating the unique SCSI ID requirement.
Multiple PV22xS enclosures, however, can still be configured for a single host. The
enclosure must be cabled directly to a separate SCSI channel on that host. A SCSI
channel does not have to be on a physically separate adapter. For instance, a mult-
channel SCSI controller such as a PERC4/DC is considered to be two SCSI channels
even though both channels reside on one physical PCI adapter. In this example, two
PV22xS can be attached to the PERC4/DC adapter. Conversely, it is also perfectly
acceptable to use two PERC4/DC adapters and attach an enclosure to each. The
maximum number of enclosures that can be configured for a single host system is limited
by the number of channels the host system can support.
Mixing EMM Speeds
There are two types of EMM modules that PV22xS supports: U160 and U320. The
numbers refer to the SCSI bus speed (in MB/sec) that the EMM is capable of supporting.
For example, U160 can transfer up to 160MB/sec while U320 EMM supports up to
320MB/sec transfer rates. One or two EMM modules may be installed in the enclosure.
When two are installed, it is required that they have the same transfer speed, which can
be easily identified with labels on back of EMMs. Mixing of U160 and U320 EMM