Dell PowerVault 220S Manual

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Dell PowerVault 220S Manual Manual pdf 23 page image

A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02PAGE 23 11/17/2005be reserved for use by the second SCSI controller. A mapping of the SCSI ID addressspace reserved by the PV22xS enclosure is shown in Figure 4-5. The HDD identifiers aredirectly mapped to it’s assigned SCSI ID, as shown in Figure 4-6.Figure 4-5 SCSI ID AssignmentsFigure 4-6 SCSI ID Numbers and Associated Hard Disk DrivesMultiple PV22xS Enclosures on a Single Host SystemDaisy chaining of Multiple PV22xS enclosures is not supported. This is due to SCSIlimitation of only allowing a maximum of 16 devices on one SCSI bus. Daisy chainingwould effectively concatenate the devices in two (or more) enclosures into a single SCSIbus, thus violating the unique SCSI ID requirement.Multiple PV22xS enclosures, however, can still be configured for a single host. Theenclosure must be cabled directly to a separate SCSI channel on that host. A SCSIchannel 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 channelseven though both channels reside on one physical PCI adapter. In this example, twoPV22xS can be attached to the PERC4/DC adapter. Conversely, it is also perfectlyacceptable to use two PERC4/DC adapters and attach an enclosure to each. Themaximum number of enclosures that can be configured for a single host system is limitedby the number of channels the host system can support.Mixing EMM SpeedsThere are two types of EMM modules that PV22xS supports: U160 and U320. Thenumbers 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 to320MB/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 canbe easily identified with labels on back of EMMs. Mixing of U160 and U320 EMM