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What is iSCSI?Answer: iSCSI (Internet SCSI) is a protocol that encapsulates SCSI (Small Computer System Interface) commands and data in TCP/IP packets for linking storage devices with servers over common IP infrastructures. By using iSCSI, you can supply high performance SANs over standard IP networks like LAN, MAN, WAN or the Internet. The iSCSI standard was defined and ratified by the IETF (Internet Engineering Task Force) in early 2003 to ensure interoperability. Which software initiators are available for iSCSI?Answer: The most recent tested and supported OS versions and SW initiators can be found listed on our firmware release notes or you can contact your nearest SANRAD offices for details. What hardware iSCSI adapters are available?Answer: In addition there are TOE (TCP/IP Offload Engine). NICs, that offload the TCP/IP processing, e.g. Alacritech SES1001, which is an iSCSI dedicated TOE. The most recent tested and supported OS versions and SW initiators can be found listed on our firmware release notes or you can contact your nearest SANRAD offices for details. What is NAS, IP Storage and IP SAN?Answer: IP Storage are external RAID enclosures that support iSCSI thus allowing servers to connect to the RAID storage systems over IP instead of traditional protocols like SCSI and FC. IP SANs are true SANs (Storage Area Networks) that allow a few to 100's of servers to attach to an infinite number of storage volumes using iSCSI over TCP/IP networks. With IP SANs you can scale the storage capacity to 100's of Tbs with any type and brand of storage system. In addition, you can use any type of network (10,100,1000) and combine operating systems (MS, Linux, HP-UX, Solaris, AIX, Netware) within the SAN network. IP-SANs also include mechanisms for security, data replication, multi-pathing and high availability. What is the difference between iSCSI and NFS/CIFS?Answer: iSCSI, NFS (Network File System) and or CIFS (Common Internet File System) allow access to information over IP networking infrastructures. NFS and CIFS were designed to transfer complete files (as in NAS), while iSCSI was designed to transfer data between servers and storage systems at the block level (as in SAN), similar to how servers read and write to internal disk drives. iSCSI block level storage access can offer superior performance (up to 10 times faster) than NAS and provides open interoperability with all applications including data bases and other performance intensive applications. Why has TCP/IP not been used for SANs before?Answer: All SANs are block based. Before iSCSI, there was no protocol that provided block based access over IP networks. Now that iSCSI is available and broadly supported, SAN’s are available for IP networks. In addition, 1 GbE is a common standard and will in the future follow with 10 GbE. 10 GbE, IP SAN performance will be higher than in current FC (Fibre Channel) technology. Why should I use iSCSI?Answer: What do I need to run iSCSI?Answer: On the host side you will need to use an iSCSI initiator. The initiator is a driver that handles the SCSI traffic over iSCSI. The initiator can be software or hardware (HBA). OS native initiators or other SW initiators use the standard TCP/IP stack and Ethernet HW while iSCSI HBAs (host bus adapters) use their own iSCSI and TCP/IP stacks on board. Do I need to build a separate network for iSCSI SAN?Answer: No, in most cases you do not. One of the major advantages of iSCSI vs. Fibre Channel SANs is that you can determine the level of separation between your different networks. For example, you can utilize all your IP traffic, including iSCSI, on the same infrastructure and network, or create logical separation on the network infrastructure, or use rigid separation in all HW and logical networks. In some cases, however, it might be desirable to separate storage traffic into a dedicated network for performance reasons. This is especially true for installations, which do not use GbE NICs or HBAs. Has the iSCSI standard been finalized yet?Answer: Yes. In the beginning of 2003 the IESG approved iSCSI draft 20 as a Proposed Standard. See http://www.ietf.org/rfc/rfc3720.txt Can I do storage virtualization within an iSCSI / IP SAN?Answer: Storage virtualization is not done at a protocol level, this is true for Fibre Channel protocol as well. A virtualization device, like SANRAD’s V-Switch, can create custom volumes from all the pooled storage capacity and deliver access to these volumes to servers attached over IP networks. What does a target and initiator mean?Answer: All storage protocols, FC, pSCSI, iSCSI have two ”ends” in the connection. These ends are the Initiator and the Target. In iSCSI we call them iSCSI Initiator and iSCSI target. The iSCSI Initiator: Requests, or initiates, any iSCSI communications. It requests all SCSI operations like read or write. An initiator is usually located on the host/server side (either an iSCSI HBA or iSCSI SW initiator). Can I use iSCSI to boot a diskless machine?Answer: Yes. When using an iSCSI HBA you can connect a diskless computer to an iSCSI (virtual) volume over the network. This disk can be used as the boot device of the machine. In the future it will be possible to boot from iSCSI volumes even without a HBA. There is a future standard from the IETF that will support this issue. IP SAN V-Switch 3000 | ISCSI V-Switch 2000 | Disaster Recovery & Data Replication |
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