Dell PowerVault MD1000 SAS Solution Manual

Dell PowerVault MD1000 SAS Solution Manual Manual pdf 5 page image

A REFERENCE GUIDE FOR OPTIMIZING DELL™ MD1000 SAS SOLUTIONS VER A00PAGE 5 5/06/2005The paper presumes that the reader has a basic understanding of different RAID levels andinterconnect technologies – such as Serial Attached SCSI (SAS) and PCI Express. In this paper,we will focus on Serial Attached SCSI storage technology, specifically for Dell’s PowerVaultMD1000 storage expansion enclosure and Dell’s PERC 5/E RAID controller. Other storagetechnologies such as SCSI or Fibre Channel, as well as topologies such as Network AttachedStorage (NAS) or Storage Area Network (SAN) are outside the scope of this document. All storageapplications will be treated independent of any specific host system or server.Serial Attached SCSI (SAS)The SCSI (Small Computing System Interface) protocol originated more than 20 years ago and isused in the majority of server storage needs (e.g. storage that is internal to a server or physicallyconnected to a server in an external disk expansion enclosure). The market prevalence of SCSIhas created economies of scale making it one of the most affordable storage interconnecttechnologies available today. Many businesses rely on SCSI physical disks to help deliverextremely cost-effective and reliable storage. In fact, SCSI physical disks have advanced over theyears offering increased performance and more sophisticated features with each iteration.However, given the inherent limitations of its parallel architecture, the current version of SCSIphysical disks, U320 or Ultra320, will be the last version of the traditional SCSI technology.Serial Attached SCSI (SAS) is a major iteration of SCSI technology and introduces a host ofbenefits when compared to older SCSI technology including,Dramatic improvement in bandwidth performance• The first generation of SAS will support 3.0 Gbps (or 300 MB/sec) per “lane”• Ultra320 SCSI is the shared-bus architecture. SAS introduces a point to point topologyenabling systems with many physical disks to scale bandwidth far beyond the bandwidthcapacity of Ultra320 SCSI.Figure 1: Parallel U320 SCSI bus versus point to point Serial Attached SCSI connection• SAS introduces the concept of port aggregation to storage interconnects. External storagedevices can connect via a x4 (“by four”)wide-lane. Cabling aggregates four SAS lanes, eachoperating at 3.0 Gbps, for a full external connection bandwidth of up to 12.0 Gbps on a singleconnector.Up to 3.0 Gbps per linkUp to320 MBps