Dell PowerVault 220S Manual

Also see for PowerVault 220S: Installation guide Manual Notice Updating firmware Service manual

Dell PowerVault 220S Manual Manual pdf 20 page image

A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02PAGE 20 11/17/2005The primary EMM must always be present. Regardless of whether SES redundancy isavailable, the secondary EMM slot must always have either a EMM or Terminator moduleinstalled to properly terminate the SCSI bus. Leaving this slot unpopulated is notsupported and will have undesirable consequences.Configurations with two EMMs and one cable connected provide a level of redundancy.Even though there is no data path redundancy, there is enclosure managementredundancy. The redundancy, however, is provided in the form of the SES enclosuremanagement services to monitor and control critical functions such as temperature, fanspeeds, initiating warnings/alerts, and in the worst case scenarios to safely power downthe enclosure to prevent any potential damage under adverse thermal conditions. SESfunctions by default are performed by primary EMM. In the event there is a catastrophicfailure of the primary EMM, the secondary EMM automatically will detect this event andperform enclosure management functions.Split Bus TopologyThis topology splits the PV22xS into two halves, essentially providing two independent,electrically isolated, SCSI busses capable of supporting up to seven (7) HDD on each bus.Because the two busses are electrically isolated, this allows simultaneous SCSItransactions on each bus. Two cables are required, one connected to each EMM. Thecables can attach to two host systems (Figure 4-2) running different applications andoperate completely independent from one another, or they can be connected to two SCSIchannels on a single host system (Figure 4-3) to increase performance by splitting the I/Otraffic between two different physical data paths In either case, it is highly recommendedthat both halves of the PV22xS be connected to the same type of SCSI RAID controllers(e.g. PERC4 and PERC4 or PERC3 and PERC3). The primary EMM monitors the stateof the seven HDD in slots labeled 0 thru 5, and 8. The secondary EMM monitors thestate of the seven HDD in slots labeled 9 thru 15. SES management is provided by bothEMM modules to their respective SCSI hosts. SCSI failures on one bus will not affect theother bus. Power and enclosure cooling, however, are shared. Power disruptions (e.g.,power short on a HDD) will affect both busses equally.Figure 4-2 Split Bus Cabling to Two Host System