iStorage Server Ultimate

iStorage Server is an IP SAN solution that allows you quickly export existing storages such as disk images, physical disks, partitions, CD/DVD-ROMs, tapes or any other type of SCSI based devices and even a variety of popular CD/DVD images to its client machines, which delivers immediate benefits allowing storage to be consolidated, virtualized and centrally managed. iStorage Server also provides RAID-1 (mirror) feature, which allows you create two devices for mirror backup, the mirror devices can be local image files or remote iSCSI devices. iStorage Server has been added support for Microsoft Virtual Disk File (VHD) and VHD snapshots at the recent release.

Compares between KernSafe iSCSI SAN and XTremeSAN

Features Free Standard Ultimate SDK
CHAP user authentication
Number of concurrent connections per target 5
Unlimited Unlimited *1
Number of Targets can be created Unlimited Unlimited Unlimited *1
Number of connections per initiator-target nexus (Multiple connections feature) 1 Unlimited Unlimited *1
iSCSI RAM disk support
Standard image disk device support
Multi-user mutual CHAP authorization support
Virtual CD/DVD-ROM emulator support
Virtual CD/DVD-RW burner with auto-loader support
Generic SCSI device (SPTI) support
RAID-1 (Mirror) feature
Asynchronous Replication over Internet *1
Automatic snapshot replication *1
High-availability (failover) feature (<2T)
COW protection (Virtual Write) *1
Virtual Hard Disk (VHD) support *1
Virtual Hard Disk (VHD) snapshot
Image File (IMG) snapshot
Volume Shadow Copy Compatible
Windows GUI control application
IPsec on-the-fly iSCSI network line encryption
I/O read and write caching
Security disks for each client, each client use own disk which use CHAP password encrypted *1
IP address and mixed authentication mechanism *1
CHAP user management tool
Network-bridged(exports an existing partition, disk, CD/DVD-ROM to clients as a virtual iSCSI drive)
Remote Burning (via SPTI)
Remote Tape Backup (via SPTI)
Vendor Specified CDB support (via SPTI)
True real-time Continues Data Protection (CDP) *1
Software RAID *1
Distributed iSCSI SAN(Datacenter) *1
CHAP users counts  Unlimited 
Client side snapshot management
Storage Pool and Snapshots
*1 It depends on which license do you have.