StableBit’s DrivePool is a popular Drive Extender alternative. Unfortunately at this time it doesn’t support any type of parity information.  DrivePool is available for Windows Home Server 2011, Windows Small Business Server 2011 Essentials, and Windows Storage Server 2008 R2 Essentials.  I’m not going to post screen shots here, as StableBit’s website has a plethora of their own images of every possible option.

Ease of Use

DrivePool is extremely easy to use.  Simply run the installer and within a few minutes the DrivePool Addin will be available in the Windows Home Server 2011 Dashboard.  Adding a drive is as simple as clicking the “Add drive to the pool” link in the Dashboard.  The free space on the drive is instantly available to the pool.  To make the files currently on the drive be managed by the pool, simply move the folder from the drive (which is still accessible) to the pool, which is available natively under a new drive letter.  As the files move, the drive statistics will be updated and data will be protected if set up to do so. Unfortunately, writing directly to the drive letter does not result in automatic duplication.

Drive and DrivePool listings

There is no concern over lock in, as native file systems are used for all storage.  DrivePool simply offers a virtual interface to treat them all as one large disk and manage duplication.  DrivePool can also manage free space, ensuring equal distribution across all available drives.  This is probably less important if the drives contain no “non pooled” usage, as DrivePool will simply utilize disks where space is available.

The above listings was from the command line.  Listing the directory within the pool produced slightly surprising results, as the list was not in order by file name as is typical, but by drive number.  Windows Explorer assigns its own ordering, so this difference is not visible outside of the command line listings.  Also, it is merely coincidence in this case that Drive 3 contains a complete list.  In larger directories, the distribution was much more evenly balanced.

Rebalancing rules are easily configurable through the Dashboard settings and custom balancers can be written as plugins.  With an additional purchase of StableBit Scanner, DrivePool can start evacuating drives that have S.M.A.R.T. warnings by either moving all files or only files that are not duplicated.

Removing a drive is really where this solution beats Windows 8’s own pooling, Storage Spaces.  Simply put, it’s possible!  In fact, there are two choices when removing a drive from the pool.  Assuming the pool is duplicated, the option to remove immediately and duplicate later will enable quick drive removal while scheduling the duplication to happen at a later time.  Otherwise, simply wait as DrivePool evacuates the removed drive.  In either case, once the drive is removed it will be completely empty of any pooled data.  I removed 2 out of 3 drives, both times selecting the option to duplicate later.  Obviously, this presents a scenario where, if a system did not check, I could end up losing files.  With only one drive, duplication is not possible, but the second drive did take much longer to remove as DrivePool validated and merged all contents to the single remaining drive.  When completed, a warning event was raised that showed up on the dashboard explaining that some files are not duplicated on the pool.

Notification

Notification is done through the Dashboard as events.  This works fine, since the dashboard has e-mail notification options.  Additionally, there are numerous third party utilities to monitor events and provide alternative notification methods.

Performance

I did not see a performance hit in read or write speeds to the duplicated files directories, however CPU utilization did double.  When copying a large file from a non pooled drive to another non pooled drive, explorer utilized about 12-15% CPU.  When copying to a pooled, duplicated directory, explorer was utilizing about 20-30% CPU.  This seems more like overhead in explorer than in the DrivePool.  Regardless, as this solution is intended for dedicated servers, I don’t see a huge concern with these numbers.

Verdict

Ease of Use: 5/5
Drive loss limit: 1 (minimum, assuming duplication is enabled).
Performance: 4/5
Expansion / Upgrade options: Simple
Efficiency: N/2
Cost: $20, plus $25 for Scanner if S.M.A.R.T. warnings are desired.
Viable: Yes

The only part of this solution that I dislike is that it only offers duplication.  While researching disParity, I did encounter forums of people using DrivePool simply for pooling, and using disParity for the redundancy.  As a pooling solution, DrivePool works great and is easy to use.  It does not lock in your data, so in a worst case scenario your data could still be read on any machine capable of reading the underlying file system.  The only loss here would be that directories may not be complete on individual drives, but they could easily be reconstructed with no loss.