Research On ISCSI-based Disk Array Online Capacity Expansion

At present,with the the rapid development of information technology,the demands of data high availability and safety are pushing the storage technology development.On the premise of uninterrupted data availability,how to online increase storage system capacity,backup and recovery important data have become the focus of research.iSCSI is a novel storage networking technology which transports SCSI protocol over TCP/IP network,combining the SCSI and IP/Ethernet technologies,which are standard and mature in storage and network fields respectively.iSCSI enables low-cost SAN to be deployed on ubiquitous IP network,thus becoming a key factor for rapid popularization of networked storage.RAID is the base device for storage systems and online capacity expansion is an essential function of it.Online capacity expansion function can add additional disks into RAID without suspending normal requests.In this thesis,analyze the throughput before and after the on-line expansion in different algorithms for RAID6 disk array.In this thesis,we comprehensively introduce the related theories and techonologies of online expansion,including the network architecture,network layer and network protocol of SCSI and iSCSI whose own unique characteristics.Then,analyze the mathematical model of Raid6 algorithm and how to recovery the crashed disk array.Analyze the throughtput of disk array before and after on-line expansion and carry out successfully simulation experiments.Through simulation experiments,we conclude that RAID6 has a good random reading performance when we use the larger data block because that not only write the check data on each hard disk but also write the check data on expertise hard disk.The performace of RAID6 random writing is poor.The performace of persistence writing is common.The performace is good when we use smaller data block.The throughput of RAID6 is better after disk array on-line expansion.