Storage Virtualization | FAQs & Discussions

How to Repurpose an Existing Server with Internal Storage into a SAN Storage Array

A White Paper by Tim Warden

Whether you are considering a server virtualization project or just a refresh of your server hardware, here is a low-cost SAN storage consolidation solution that could save you thousands of dollars.

Many small and medium sized businesses run their datacenters on Direct Attached Storage: each server has its own local storage, either using the server's internal disk bays or an externally attached tray of disks, usually connected to a RAID controller HBA in the server. In most cases, a large portion of the storage capacity of those servers goes unused. The capacity may be "free space" on the server or unused space already allocated to a file system, but in any case it is tethered to the server and can't easily be used elsewhere. It is not uncommon to hear of 30%-40% utilization rates with DAS, meaning that 60%-70% of your disk space is wasted.

Not only does Direct Attached Storage often result in wasted capacity, it also results in wasted money when it's time to refresh the server: you'll have to repurchase the storage as well.

Portable, Low-Cost, Easy-To-Use Software Turns Your x86 Server into a SAN Storage Array

Here's a low-cost, low-risk solution that will enable you to enjoy the benefits of a shared storage array without the associated expense. DataCore Software Corporation offers a unique software package called SANmelody™ that converts ordinary x86 PCs into SAN Storage Arrays.

Let's consider an example of a small IT department with a limited budget. Perhaps they have been considering a SAN but are being held back by the expense. They currently have a few servers, one of which is a Windows server with a few shelves loaded with SCSI drives directly attached to a RAID card. For our example, suppose the server has 4 volumes. The "C:" drive, which contains the Windows OS and applications, a drive containing user fileshare data, a drive containing SQL Server tables for a database application, and a fourth, unformatted, unpartitioned drive. This server could easily be repurposed as a SAN Storage Array.

The first step will be to migrate the server's current applications to another server or servers: perhaps a newer model with one or two Gig-E NICs integrated, but with only an internal disk for installing and booting the Windows OS and application. Install Windows and prepare the server(s) for your environment, setting IP addresses, installing the application or applications, etc.

We'll shut down the old server's applications and un-install them, taking care to leave the data volumes undisturbed. Once the server is stripped of its old responsibilities (i.e. the Windows server is back to a relatively clean state with no superfluous applications installed), we will install the SANmelody software. After the installation, we will reboot the server and allow the SANmelody software to install its storage processor daemons and drivers.

The SANmelody software will install iSCSI target drivers on the available Ethernet ports, effectively turning the server into a SAN storage array and thus allowing you to publish volumes via iSCSI over your existing IP network. Ideally, you would isolate the iSCSI traffic to a VLAN or private network segment, but it is nonetheless possible to use iSCSI over your existing network.

As a SAN storage processor, SANmelody comes with a rich feature set, with options for implementing data mirroring data replication and snapshots. SANmelody is also a high-performance solution, using the server's RAM as storage processor cache and driving the processors in a real-time I/O polling fashion.

As for storage, SANmelody can use any volume or disk that can be seen in Windows Disk Management in the MMC (Microsoft Management Console). There are three ways to use the storage in SANmelody. First, any raw, unformatted partition (primary or logical drive on an extended partition) can be turned into a SANmelody volume which can be offered to SAN clients (or Application Servers) as a new, unformatted SAN volume.

Additionally, SANmelody has a unique feature called SANmotion, by which any partition containing a pre-cooked NTFS file system can be offered to the SAN clients via "proxy". In this case, SANmelody does not disturb the existing file system geometry or contents of the volume, but simply provides a pass through allowing the volume to be mapped over the SAN. To activate SANmotion on a volume, we unmount the volume from the server (remove its drive letter) and tell SANmelody to "protect" the volume. In our example, we can use this feature to take the existing fileshare and database volumes and assign them out to our new servers over the iSCSI SAN. In the screen-shot below, you will notice are existing FileShare and SQLTables volumes have been protected by SANmelody — their volume type is "FS" for File System Volume.

On our new Application Servers, we download and install the free Microsoft iSCSI Initiator and configure it to attach to our SANmelody server, using either the netname or IP address of the SANmelody server. Using the SANmelody GUI, we create two new Application Servers to logically represent our new FileShare and SQL server hardware and assign them their iSCSI channels. Then we map our existing, virtualized FileShare and SQLTables volumes to their respective iSCSI server channels on the SAN. Rescan disks on the Application Servers, assign drive letters to the volumes, configure the file shares and SQL server and we're back in business.

The third way SANmelody can use our server's disk space is in a Thin-Provisioned Storage Pool. For this, we will use that unformatted, unpartitioned fourth volume. In this unpartitioned, raw state, the disk will shown as an available disk for SANmelody to add to a storage pool. We create a pool arbitrarily called SM1-P1, and assign the disk to the pool.

Disks can be added to a virtual storage pool at any time, without disrupting production

Creating volumes from a storage pool is as easy as right-clicking over the pool and selecting a menu. We can create as many volumes as we like from the storage pool; each volume will be sized at 2TB. We can size them smaller as we like, keeping in mind that ultimately the pool has a certain amount of physical storage associated. We can add additional physical storage to "feed" the pool at any time without disrupting our production file share and SQL servers; our virtual volumes are based on pooled storage, and not on any particular partitioning scheme.

Provisioning new Virtual Volumes from a Storage Pool is as simple as Right-Click

Storage Pooling coupled with Thin Provisioning radically simplifies the provisioning and administration of storage and allows you to fully utilize the physical disk space you've purchased. It also enhances performance. For more information on Thin Provisioning with examples, click here.

Advantages of implementing storage consolidation with SANmelody™

"I'm Ready To Get Started. How Do I Buy SANmelody™?"

Las Solanas Consulting is not a DataCore reseller — this article is published for informational purposes. However, you can purchase and download SANmelody™ from the DataCore website. The Virtual Infrastructure Foundation Kit includes a year of annual support and has all the features you need to implement our example above — and at a very attractive price. The package manages up to 3TB of logical disk space and features the Storage Pooling and Thin Provisioning feature, not to mention the sophisticated caching and I/O polling engine.

If you want to take a test drive of the SANmelody software, you can download a free, no-obligation 30-day evaluation. The evaluation software includes iSCSI and FC support, as well as support for their unique Thin Provisioning feature. You'll see for yourself how easy it is to create a scalable SAN infrastructure on a limited budget.