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StarWind iSCSI SAN Free Edition

StarWind Free is an iSCSI Target that converts any Windows server into a SAN. This is a fully functional product at no cost.

Key features:

Compare StarWind iSCSI SAN Free to Microsoft iSCSI Target

The comparison chart below contains the list of the main features of StarWind iSCSI SAN and Microsoft iSCSI Target solutions. After the comparison chart the detailed comments are provided.

Feature StarWind Free iSCSI SAN Microsoft iSCSI Target
Price Free Free, with hidden costs
Host operating systems supported Any modern Windows Windows Server 2008 R2
De-duplication Fully supported, variable block size
Served capacity Unlimited Unlimited
Number of concurrent connections Unlimited Unlimited
Usage scenarios Production allowed Production allowed
Caching Multi-level, Write-Back and Write-Through, de-duplicated
iSCSI boot Fully supported Partially supported (see explanation below)
High Availability HA storage limited to 128GB
WAN replication Upgrade is possible
CDP and snapshots Supported Snapshots only, no CDP
VSS (Volume Snapshot Services) Supported Supported

Price and host operating systems supported

Both companies offer their product free of charge. StarWind Free iSCSI SAN is really 100% free, in contrast to the Microsoft iSCSI target which can be used on top of Microsoft Windows Server 2008 R2 only. With StarWind you can use a desktop for the StarWind Free iSCSI SAN, or install StarWind on top of free Hyper-V host. Microsoft requires you to use Windows Server 2008 R2 with their target. Microsoft iSCSI Target is not a stand-alone product, it is a component to improve the functionality of their server OS. StarWind itself is a flagship product and you can use its free version without paying directly or indirectly. With StarWind Free iSCSI SAN you can build a test SAN with a server running Windows Server 2003. You can also use StarWind in a production environment without paying for OS licenses, use Hyper-V as your setup of choice.

Conclusion: StarWind Free iSCSI SAN is 100% free, but Microsoft offers their solution with hidden costs.


StarWind supports variable block deduplication, while Microsoft hasn’t implemented deduplication, nor have they announced plans to implement it in the future. What does this technology mean to our respected customers? Many SAN users run server clusters using iSCSI SANs as the shared storage provider for various hypervisors, utilizing iSCSI diskless boot and use iSCSI SANs as a destination for disk-to-disk backup. In the most commonly used scenario iSCSI SAN acts as a shared storage provider for hypervisors hosting virtual machines.
For example, a company just migrated to Windows 7 on the desktops with 50 workstations hosted on our iSCSI SAN. One virtual machine footprint is around 20 gigabytes, so using storage without deduplication they all should occupy a terabyte of disk space (50 * 20 GB = 1 TB). Using storage that supports deduplication the required capacity could be less than 100GB, since the Windows 7 OS files are duplicated across all the workstations - they are ideal candidates for deduplication. Deduplication can be also applied to backups dealing with repeated data.

Conclusion: With deduplication savings are huge and the return of investment can be huge.

Served capacity and number of concurrent connections

These features are also very important. Both companies provide solutions with no served capacity limitations and the number of concurrent connections is also not limited. You can have any setup without worrying about running out of capacity or being concerned that virtual machine migrations could fail. Some companies offer just a few terabytes of storage in their limited free versions or limiting number of iSCSI connections to just one. These configurations are not very functional and such "free" versions from numerous vendors cannot compete with the solutions developed by StarWind or Microsoft.

Conclusion: iSCSI SAN software from both StarWind and Microsoft provide unlimited capacity and unlimited number of concurrent connections.

Usage scenarios

Both StarWind and Microsoft allow using their software in production, a possibility that was not available in the past. This is a good step forward, as you can use the same target for pre-production and production without wasting time for data migration or conversion between virtual machines and physical servers.

Conclusion: Allowing production use with a Free iSCSI SAN is a great step forward that will help accelerate wider spread occurrence of iSCSI storage in the IT industry.


Any commercial deployment requires an ability to apply for technical support and software updates. Both Microsoft and StarWind provide the same basic e-mail and open public community forum support model for their free software. With StarWind there is an option to upgrade to a paid per-incident or fixed time frame premium support plan. With Microsoft additional support options are unclear yet.

Conclusion: Free iSCSI SAN versions are covered with basic support plans by both StarWind and Microsoft.


Here performance is at issue. When using an iSCSI SAN in production, the system performance is important. StarWind has a multi-level cache mechanism. It takes gigabytes of RAM from the server hardware that StarWind is installed on and converts it into extremely fast level 1 write-back or write-through cache. It’s also used to store level 2 cache data. As a result you could achieve I/O and MB per/sec values with a spindle-based storage system that is typically only available if using a full SSD equipped storage array. And you achieve this for a tiny fraction of an SSD array’s cost. Deduplication comes into play again: in a real production when used with hypervisors StarWind has a three-level cache with one level being also deduplicated. So it takes a single memory block to cache multiple virtual machine disk accesses. Microsoft has no caching so its potential for production use is severely limited compared to StarWind.

Conclusion: StarWind Free has advanced caching making it far more performant in production scenarios than Microsoft.

iSCSI boot

Hypervisors, VDI and iSCSI boot all walk together. It is reasonable to move all processing away from dedicated workstations and virtualize as much of your IT infrastructure as possible, including desktops gathered inside a single hypervisor cluster. As a result, the desktop clients require lower powered hardware, their costs and probability of failure are reduced, and end users are able to have the same working environment on any machine they use to connect to hypervisor, regardless of physical client hardware they are using. Both StarWind and Microsoft have all the necessary iSCSI-related features implemented inside their iSCSI SAN solutions to enable iSCSI boot. But iSCSI boot is dependent not just dependent on iSCSI. There are other services like DHCP, TFTP, and image management tools that the network administrator needs to deal with to achieve iSCSI boot. Microsoft has the iSCSI part only and StarWind has all the management control and required components embedded into a single management console making an iSCSI diskless boot configuration quite an easy task.

So, technically you can boot from both StarWind or Microsoft iSCSI targets, although in practice you will spend far less time achieving your goal if you use the solution from StarWind Software. Again, both caching and deduplication come into play when performing iSCSI boot of similar OS images. StarWind should work much faster as I/Os are cached on the server side and a StarWind-managed SAN will take less disk space as OS images contain pretty much the same data.

Conclusion: Microsoft can be used for iSCSI boot, although StarWind is far easier to manage, is faster and provides better ROI.

High Availability

Generic Windows and Linux clusters and hypervisor clusters bring applications to another level of uptime. A Hypervisor or cluster head could fail easily, it could be brought down for hardware or software maintenance and the virtual machines would be simply moved to another cluster head using any kind of a hypervisor specific VM migration. Everything works fine up to the layer where storage failures could be an issue. A storage node is just another machine that can also fail. Since we don’t run any redundancy for the storage node itself, we have a single point of failure. A failed storage node results in the entire Windows, Linux or hypervisor cluster not working. Both StarWind and Microsoft offer single node installations with their free versions. With StarWind you have a paid option to upgrade to a fully high available configuration. With Microsoft you don’t have such an option. It means that you can start using StarWind as an experimental SAN and can upgrade to a paid high availability version for full HA production use. Using a non-HA version in a production scenario may be fine for some file servers or disk backup, but leaves vulnerabilities for critical servers. Starting with Microsoft as an experimental setup and changing SAN vendor before doing production takes time and requires training on the product.

Conclusion: StarWind offers a full HA option. You can always switch to a paid version preserving the existing setup and running a simple multi-node upgrade. Microsoft does provide an HA option.

WAN replication

You keep an extra copy of the entire SAN storage data in an offsite location and if your primary storage fails you can run a recovery process from the remote site. The nature of the process assumes you have a comparably slow link between your main and backup sites so special activities are required to move large amounts of data over a slow performing replication link. StarWind offers a paid upgrade to enable WAN replication, Microsoft does not. StarWind allows you to add replication features as your requirements change or to keep initial costs down as you phase in a larger solution. Deploying StarWind initially and adding WAN replication later is a very simple upgrade. It’s the same product and same core technology based on deduplication and compression engine. Using the solution developed by Microsoft would require extra time spent on evaluation, testing, training and deployment of a third-party replication solution. And the resulting solution would not necessarily be better compared with StarWind’s built-in WAN replication.

Conclusion: StarWind saves time and money providing WAN replication as a paid upgrade option, while Microsoft doesn’t provide WAN replication.

CDP (Contiguous Data Protection), Snapshots and VSS (Volume Snapshot Services)

Snapshots and their logical evolution called CDP are critical to anybody who would like to have backup integrated with a SAN. With snapshots and CDP it is easy to recover any file corrupted or destroyed by user activities or any external influence (virus, disk failure, power outrage etc.). You have multiple copies of the same file and each copy represents up-to-date data for today, yesterday, a week ago and so on. Snapshot frequency is configurable by IT administrator. VSS is a Microsoft developed feature allowing you to have consistent snapshots. VSS asks all active writers to hold their writes in some known state and flushes the file system cache before taking a snapshot. This allows completed transactions to be written to disk. Nearly 100% of server-based applications are VSS-aware. Both Microsoft and StarWind offer snapshots which are VSS compatible. StarWind also offers CDP in their free version as well. CDP could be thought of as all-time-snapshot, so every single write is tracked and logged. This means with StarWind you can roll back to virtually any state of a working file.

Conclusion: Both companies offer VSS-compatible snapshots but StarWind solution is preferred, as CDP provided by StarWInd offers near point-in-time recovery compared to manual snapshots done by Microsoft.

Download StarWind Free

To proceed to the installer download and get your personal free license key, please click this link:

Please fill out the form below to download the product. An installer link together with the license key will be sent to the e-mail address that you’ve specified. You may check the Free vs. Paid document if you are unsure about which StarWind Virtual SAN version you would like to try. Aside from this, there is a totally unrestricted NFS (Not For Sale) version of StarWind VSAN available for certain use cases. StarWind Virtual SAN for Hyper-V release notes are available here.