The iSCSI solutions discussed in this report are managed using the Microsoft iSCSI initiator. The storage volumes can be managed using standard Windows tools such as “Disk Management”. In addition, most iSCSI target storage solutions provide Microsoft VSS and VDS hardware providers and can be managed with Microsoft Storage Manager for SANs (SMfS), which is available in Windows Server 2003 R2.
Storage Performance and iSCSI
One of the concerns about iSCSI is the overall performance of the solution, including the load on the host CPU, the iSCSI target performance, and the Ethernet network performance, especially during periods of heavy I/O. Although this report is not intended to be an exhaustive performance benchmark, some of these performance issues will be discussed.
iSCSI solutions are a blend of traditional network and traditional storage technologies, and most of the iSCSI storage solutions are pre-configured to provide good overall network and storage performance. Administrators may choose to fine-tune various advanced network and storage settings for additional performance or configuration purposes.
The implementations discussed for the various iSCSI target solutions were intentionally disparate to illustrate the variety of ways in which iSCSI targets can be deployed and the configurations discussed for individual products were not necessarily optimized for performance. As a result, the performance of the iSCSI target solutions varied widely, due to the variety of designs and components used. These storage solutions used a variety of storage devices, including SATA disk drives, SCSI (parallel) and SAS disk drives. The disk drives spun at various RPM including 7200, 10K and 15K RPM. Each storage array had a different number of disk drives in the array. Different RAID stripe sizes were used with different arrays. Various disk subsystem caching designs were used, not all of which have been publicly disclosed.
Basic I/O tests were performed with IOMeter, an open-source I/O load generator. The same group of block sizes and I/O patterns was tested with each iSCSI target solution; however the queue depth was varied as an additional data point. Some of the iSCSI target solutions supported multi-path I/O, and where possible, multiple paths were used. The deployment scenarios outlined below include up to 2 sessions. Although the purpose of these tests and this report is not to be a head-to-head performance comparison of the iSCSI target solutions, performance was measured in order to provide some general reference points for the expected performance range of iSCSI target solutions. Some interesting reference points comparing various types of network adapters in the host servers (iSCSI initiators) were also made. The IOMeter test results for each iSCSI target solution are included in their respective sections. Readers should take notice that IOMeter testing is by no mean a substitute for workload testing and modeling. In addition, tools from Microsoft such as LoadSim for Microsoft Exchange and SQLIO and SQLIOSim for SQL Server can be used to test how an iSCSI initiator and target respond for those particular applications.
IMPORTANT NOTE: the iSCSI targets presented in this white paper are different in class, price, and disk I/O characteristics, so head-to-head comparison of the iSCSI targets in the context of this report is not possible. In addition, the tests were run with different parameters to emphasize that this report is not a benchmark report.
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