iSCSI Targets

The savings are even greater if you're planning for disaster recovery by linking storage from multiple locations. You can send iSCSI traffic across your WAN links--assuming you've got sufficient bandwidth--by just routing the traffic. In contrast, sending Fibre Channel traffic across a WAN would call for Fibre Channel to IP routers or switches, sending your cost well into five figures.

Because iSCSI uses standard Gigabit Ethernet, you may want to implement access controls so only authorized servers can access an iSCSI logical drive. Typically, iSCSI devices can limit access to logical drives by IP address, IQN (iSCSI qualified name) and/or CHAP (Challenge Handshake Authentication Protocol).

Of course, a SAN is nothing without storage, so you'll need to hook up a disk array or three. Since most vendors figure iSCSI customers are looking for more bang for the buck, today's iSCSI disk arrays use SATA (Serial Advanced Technology Attachment) drives to take advantage of their lower cost and higher capacity. Before you reject SATA as for server storage, take a look at how the disk-drive industry has changed in the past few years.

iSCSI Arrays

As recently as the turn of the millennium, the disk-drive market was split into high-performance and -reliability server drives with SCSI or Fibre Channel interfaces and low-cost desktop drives. Over the past few years, the market has become even more differentiated, with ATA and SATA drives designed with low noise levels--especially for consumer electronics applications like TiVos--and high-reliability drives designed to the same million-hour MTBF (mean time between failures) as SCSI and Fibre Channel drives. Now SATA drives have features like hot-swappability and native command queuing that were long reserved for SCSI or Fibre Channel.

We put out the call for iSCSI disk arrays and received products reflecting a full range of functionality. We tested Adaptec's iSA1500 Storage Array, EqualLogic's PeerStorage Array 100E, FalconStor's iSCSI Storage Server, Intransa's IP5500, Overland Storage's REO 4000, Promise Technology's VTrak 15200 and Snap Server's 18000. Lefthand Networks and Stonefly declined to participate, while Network Appliance and SANrad didn't have equipment available to meet our schedule.

These products fall into three groups. At the high end, the Intransa IP 5500 and EqualLogic Peer Storage Array provide room to grow by treating a group of disk cabinets as a single storage resource. With these systems, if you run out of disk space you just add another drive cabinet. The drives in the extra cabinet are added automatically to the group. Even better, as you add drive cabinets and/or Intransa controllers, you also add Gigabit Ethernet connections to the virtual IP address of the group. You can expand these systems to 50 TB or more while improving performance.With iSCSI SANs taking on primary storage tasks, such as supporting server clusters and critical messaging and database servers, iSCSI arrays are gaining support for enterprise array features, including snapshots and replication. Snapshots let you store and then mount the state of a disk at a point in time as an additional disk for reference or backup. All the systems that support snapshots use similar copy-on-write technology. This copies the current contents of a disk block to the snapshot area of the disk when the block's contents are changed.

Manual or scheduled snapshots are useful as part of data protection, but they may not always give you valid data, because they don't coordinate with the server's apps to make sure the data is consistent at the snapshot's creation. You're better off with a system that uses Microsoft's VSS (Volume Shadow-copy Service) or other agents to tell an app--like a messaging or database server--to flush its buffers and queues so a snapshot can be taken. FalconStor and Intransa ship VSS providers, while Adaptec and EqualLogic promise to have them available by year's end.

The lower-end products we tested provide basic iSCSI disk functionality. The Promise VTrak 15200 cannot perform LUN masking, but it makes up for this shortcoming in bang for the buck. Where else can you get more than 3 TB of RAID 5 networked storage for less than $10,000? Adaptec's iSA1500 includes support for LUN masking, disk virtualization and even snapshots, but its 1-TB capacity and lack of expansion put it in the basic class.

The third and most interesting group includes devices that combine iSCSI disk targets with other functionality. The Overland REO is primarily a backup appliance emulating tape drives as well as acting as a disk array. The Snap Server 18000 and FalconStor's iSCSI Server running on a Dynamic Network Factory IPBank-E 1600 are NAS boxes with iSCSI functionality baked in.With high marks across the board in performance, functionality, management and price, the FalconStor product wins our Editor's Choice award. We give an honorable mention to the EqualLogic PeerStorage Array 100E: It's ideal for users who need massive expandability.

FalconStor wisely deduced that there's a sizable demand for iSCSI disk systems for Windows shops. So it created its iSCSI Storage Server software for Windows Storage Server, the NAS version of Windows Server 2003.

When we told FalconStor we were testing disk-array targets, it had one of its OEMs, Dynamic Network Factory, send us a 3U IPBank-E 1600 appliance preloaded with Windows Storage Server and iSCSI Storage Server.

We expected to find a solution like the Snap Server 18000's that provided iSCSI functionality without any flashy features or earth-shattering performance. What we got was the most impressive of the products we tested, with high-end performance and enterprise features at an almost unbelievable price.

The iSCSI Storage Server adds an iSCSI tab to the Windows Storage Server Web interface, so we configured the server through the GUI without having to refer to the manual. Dynamic Network Factory had preconfigured the disk drives into a RAID 5 set, so our next step was to create a series of LUNs. Unlike the Snap Server 18000, which creates an iSCSI LUN as a file within the file system, iSCSI Server creates LUNs from raw disk space, limiting overhead in the process.When it comes to data protection features, the iSCSI Storage Server has just about every feature we could think of (even though some of them require you to buy additional feature licenses). You can take snapshots manually, on a schedule or triggered through your backup application and Microsoft's VSS. FalconStor even has snapshot agents for SQL Server and Exchange so you can take coordinated snapshots of those databases without VSS.

Recognizing that applications like Exchange and SQL Server store their database on one volume and related log files on another, iSCSI Server can group LUNs so snapshots of the entire group are synchronized. The iSCSI Server manages snapshot space dynamically, whereas others require you to specify the amount of snapshot space when you create a LUN. In addition to underlying RAID protection, the iSCSI Storage Server can create LUN mirrors on separate RAID arrays to protect your data against RAID controller failure. If that's not enough, you can buy the cluster option and run a pair of iSCSI Storage Servers.

After acquiring the feature license, you can tell iSCSI Storage Server to replicate data from one iSCSI server to another for disaster recovery. Let's be clear here: This is not real-time replication like you get with EMC's SRDF (Symmetrix Remote Data Facility). The iSCSI Storage Server lets you schedule replication as frequently as on the hour. At the appointed time, it takes a snapshot, replicates the snapshot to the target and rolls it forward to bring the replica up to date.

If 4 TB of SATA disk isn't enough for you, Dynamic Network Factory just announced a 7U behemoth just coming to market with 42 SATA drive slots, which could be as much as 16 TB using the 400-GB drives. Since FalconStor sells its software products through multiple OEMs, we expect an expandable NAS appliance with iSCSI server soon.

Amazingly enough, Dynamic Network Factory manages to put this all together for $7,000. Fast, flexible, easy to manage and cheap to boot--what's not to like?iSCSI Storage Server on IPBank-E 1600, starts at $6,000. FalconStor Software, (631) 777-5188. www.falconstor.com

When we were unpacking the EqualLogic PeerStorage Array 100E, it looked like what we had expected: an iSCSI disk array to be. With lots of high-capacity drives in a 3U enclosure with a couple of Gigabit Ethernet ports coming out the back, it was very similar to the Promise vTrak. However, once we saw what it could do, our attitude changed. Except for its use of SATA drives, the PeerStorage Array is more like an EMC or Hitachi array with snapshots, replication and redundant everything. Each PeerStorage cabinet has redundant controllers with three Gigabit Ethernet connections.

But the real fun starts when you add a second cabinet to your iSCSI SAN. You can form a single group with up to 32 PeerStorage arrays. Like an Intransa realm but without all the back-end Gigabit Ethernet cables, a group is a virtual RAID array that shares resources like free space and hot spare drives. Performance grows along with disk space, since adding another array translates to three more load-balanced Gigabit Ethernet ports.

We hooked up the laptop and ran the text-based setup script. It prompted us for IP addresses for this cabinet and the virtual IP address for the group. We then fired up a Web browser and started creating volumes. When we created a volume, we had to enter its size, the amount of space to hold for snapshots, and to which servers we wanted to limit access. In addition to the usual IQN and CHAP restrictions, it was even easier to just limit volume access by IP address.

The PeerStorage Array can create snapshots on command through its GUI or on a schedule. It can even make snapshots available automatically, adding a time stamp to the end of the volume's IQN to create the snapshot's IQN. You can also create clones, like Intransa replicas, or mirrors.The really exciting part came when we unpacked the third PeerStorage Array and set it up as a second group. We then configured the two groups to be replication partners and started replicating volumes from one group to the other. Like FalconStor's iSCSI Server, the PeerStorage Array takes snapshots of the source volume and replicates them to the destination volume on a schedule. The only thing we can really complain about is that when you choose a RAID level, 1+0 for performance or 5+0 for space, you're choosing it for the whole group. Having one 30-TB free space pool is nice sometimes, but we'd rather have a fast pool and slightly less expensive pool.

PeerStorage Array 100E, $39,900. EqualLogic, (888) 579-9762, (603) 579-9762. www.equallogic.com

Intransa's IP5500 presented a surprising architecture. Rather than the 3U box of disks with Gigabit Ethernet coming out the back, the IP5500 came in three boxes. In total, a 3U disk cabinet with 16 250-GB SATA disks and four--count 'em, four!--disk controllers (one for each row of four drives) and a matched pair of 1U servers acting as redundant iSCSI controllers. The controller 1U servers communicate with the disk cabinets via iSCSI as well, requiring eight ports for each disk cabinet, a teamed pair for each disk controller and two ports for each controller. That's a total of 12, in addition to the four ports (two for each controller) to connect the IP 5500 to our iSCSI SAN and management networks.

Within a realm, which is what Intransa calls a set of interconnected disk cabinets and controllers, the load is automatically balanced across all the controllers. If a controller fails, its connections to the servers are picked up by the other controllers providing controller fault tolerance. A realm can have up to eight controllers and 12 disk cabinets, for a total of 48 TB.

Because Intransa includes installation in the price of the IP 5500, we let the vendor send a field engineer to the lab for installation. We created a VLAN on the Extreme Summit7i switch for the internal communications, and in a few minutes, the engineer had the system up and running.We then installed the StorControl Windows management application on our management PC and started configuring our realm. Rather than create a single large RAID set and subdivide it into logical drives, we created LUNs, which Intransa calls volumes, and let the system allocate space from the realm based on our policy and fit. All volumes use some form of RAID 1 or 10. Policies determine how many physical drives the data should be spread across, so we picked the speed policy to spread it over eight spindles. Fit determines how physical drives should be shared with other volumes, so we chose "New," which placed each volume on its own set of drives.

When assigning volumes to initiators, we were pleasantly surprised to find that the IP 5500 kept track of all the initiators that had tried to connect to it. This meant we didn't have to type those pesky IQNs.

The IP 5500 supports both multifaceted mirrors and snapshots. You can create up to three mirrors of a volume and break mirrors off at any time after they're synchronized to have a standalone copy of the data. You can create snapshots from the GUI or command line. Intransa has a VSS provider for creating snapshots from Windows 2003 servers programmatically. Once snapshots are created, you can assign them to initiators and roll back from the GUI. The IP 5500 is the only product we tested that provides extensive event logging, graphical performance and throughput displays through its GUI.

The IP 5500 is a powerful system with massive expandability, but it costs a bundle. The $60,000 entry price for a system that uses SATA drives and requires yet another Gigabit Ethernet network to connect its components together isn't all that compelling.

Intransa IP5500, starts at $60,671 for 2 TB. Intransa, (408) 678-8600. www.intransa.comLong a volume leader in the small and midrange NAS market, Snap Appliance, now a division of Adaptec, is moving uptown with its first dual-processor appliance: the 3U, 2-TB Snap Server 18000. The latest version of Snap's Linux-based Guardian OS, which runs on Snap servers from the 4500 on up, includes iSCSI support, so our Snap Server 18000 is not just a NAS appliance, but an iSCSI disk system as well.

If you outgrow the Snap Server 18000's 1.5 TB of RAID 5 capacity, you can connect up to seven Snap Disk 30 expansion cabinets through the Snap Server 18000's Fibre Channel interface. Each Snap Disk 30 holds 16 250-GB drives, which gives the Snap Server 18000 up to an impressive 30 TB of raw disk space.

Installing the Snap Server 18000 was simple enough. We plugged its dual Gigabit Ethernet ports into our iSCSI SAN and used the Snap Server Manager, from a machine on the same subnet as the Snap Server, to assign an IP address to the load-balanced Ethernet ports. We could then manage the Snap Server from its internal Web server. Note that all management is in-band, so if you're planning to use iSCSI HBAs that don't also provide IP access to the network, you may have to set up a management station with access to the iSCSI net.

Each iSCSI disk target on the Snap Server is stored as a file in one of its Linux volumes, so we created a RAID set from all eight 250-GB drives, created a volume on that RAID set and then created the four 100-GB iSCSI disks for performance testing. The Snap Server doesn't provide for LUN masking by IQN or IP address, but you can set up independent local user IDs and passwords for each iSCSI disk and use CHAP to authenticate.

Although Snap's guardian OS supports both volume snapshots and replication, these features aren't supported for iSCSI volumes. If you're using a Snap Server primarily for iSCSI storage, you should reduce the amount of disk reserved for snapshots, since you won't be using this feature.Combining file and block storage in a single, relatively high-performance device that's expandable to 30 TB is very appealing. Many organizations would be well-served to consolidate all their storage into a Snap Server, with users accessing the shared file systems while Exchange and SQL servers use iSCSI to access their data.

Snap Server 18000, $142,960 (fully configured 30-TB system). Snap Appliance, (888) 310-SNAP, (408) 795-3600. www.snapappliance.com

The smallest of the products we looked at (with 1U and 1 TB of raw disk space), Adaptec's iSA1500 could be a good choice for organizations that want to cluster a few servers. Despite its size, the iSA1500 has some advanced features, including snapshots--and Adaptec promises both a VSS provider and replication for future firmware releases.

We connected the iSA1500 to our KVM switch and used the command-line interface to give it a name and other basic setup information, such as IP address. We then connected the management and two iSCSI data Ethernet ports to our network and installed Adaptec Storage Manager on our management PC. Wait ... scratch that. We attempted to install it.

Adaptec Storage Manager consists of a management Web server that installs on Port 8000 of your management server and a client that you can install on your servers to simplify using iSCSI resources. Unfortunately, when Microsoft updated its iSCSI initiator, it broke Adaptec's Storage Manager client. A download from the Adaptec site solved that problem.The client interacts with the Microsoft iSCSI initiator and Windows, so you can use Adaptec Storage Manager to create a volume on a server and have it create the LUN on the iSA1500, connect the iSCSI initiator, assign the LUN to that server's IQN, partition and format the drive, and assign the drive a letter.

That meant creating a RAID set--or, as Adaptec calls it, a storage pool--creating LUNs from the RAID set and assigning initiators to the LUNs. Aside from the usual CHAP authentication, the iSA 1500 was the only product we tested that supported IPsec encryption. The programmer who created the Web interface was perhaps a bit overzealous in enforcing the official format for IQNs, rejecting the name of one of our servers if we typed the machine name portion in upper-case letters, which is how the Microsoft initiator reported it to us.

All in all, the iSA 1500 is somewhat disappointing. It has most of the important features, but its limited performance and expandability left us cold. To some extent, we wish Adaptec would put the iSA 1500's features on box with more drive slots and a bit more horsepower.

Adaptec iSA1500 Storage Array, $6,800 (as configured). Adaptec, (800) 442-7274, (408) 945-6000. www.adaptec.com

Promise Technology has long been a leader in the low-cost ATA RAID world, and its VTrak 15200 is its first foray into networked storage. A 15-drive SATA enclosure with dual Gigabit Ethernet ports for iSCSI access, the VTrak 15200 is a solid--if somewhat basic--iSCSI array that would be a good choice for small server clusters and disk-to-disk backup applications.Promise sells the VTrak 15200 enclosure and controller through value-added resellers and system integrators. VARs can fine-tune the configuration using Western Digital Raptors for a database server or 400-GB, 5,400-RPM drives for a disk-to-disk backup application. Promise arranged for Western Digital to provide eight 250-GB SATA Caviar drives for our tests.

You can upgrade from another Promise array controller or enclosure and transfer your existing drives, maintaining the existing RAID sets and their contents.

After racking up the VTrak and mounting the eight SATA drives in their sleds, we started the configuration by connecting a PC to the serial port and setting the management port's IP address through the menu-driven interface. Next, we installed the WebPAM management app on a server. WebPAM installs a Web server on Port 8080--or 8443, if you've configured it to use SSL--which serves up the Java app you're using to administer the array.

This install of a Web server on the management station is our least favorite form of management application. A station used for managing a variety of systems ends up with multiple background processes running all the time. Vendors, if you're going to give us a Web/ Java application to manage your appliance, put the Web server on the appliance, too.

We created logical drives by selecting a RAID level, block size and the physical drives we wanted to include. Because a VTrak logical drive is a full RAID set, the only way we could create four LUNs for performance testing was to create four RAID 1 sets. We then assigned the logical drives to iSCSI ports and LUNs. We expected that using RAID 1 when most of the competitors were running RAID 5 would have given the VTrak a performance advantage, but as it turned out, it was among the slower systems we tested.Unlike the other tested products, which present an iSCSI target complete with IQN for each logical drive, the VTrak 15200 presents itself as a single target with multiple LUNs on each of its two Gigabit iSCSI ports. This means that when you log in to the VTrak using most initiators, all the LUNs assigned to that Ethernet port become available to the server. Since the VTrak doesn't provide any LUN-masking capabilities, administrators will have to make sure to limit servers to only those drives that are necessary.

Once VTrak's software is capable of both basic LUN masking and subdividing a RAID set into multiple LUNs--features the vendor plans to have by early next year--VTrak will rise to the level of full-blown SAN array. Today, it's a low-cost solution for clustering and other applications that don't require a more than a few servers to share an array.

VTrak 15200, $5,999. Promise Technology, (800) 888-0245. www.promise.com

While the makers of most of the iSCSI disk arrays we tested promote disk-to-disk backup as an appropriate use of their products, Overland Storage's REO 4000 goes one step further by emulating tape drives as well as acting as an iSCSI--or optionally, Fibre Channel--disk array. For more information on the REO 4000's tape-emulation features, see "Marriage of Convenience,".

To install the REO, we connected the management port to our primary network and the two gigabit data interfaces to the iSCSI SAN. We then opened a browser and started configuring the system through its internal Web server.The REO 4000 treats its drives as two RAID sets, but you have to configure the entire 2 TB of raw space as a JBOD, RAID 0 or RAID 5 array. Assuming you, like most admins, consider fault tolerance good, you'll have 1.5 TB of usable space to allocate to iSCSI disks.

Once the RAID was set up, we clicked on "Add Logical Volume" to create iSCSI targets. The default target names are not fully qualified iSCSI names, so you'll have to be careful that you don't create duplicates if you have more than one REO on your network. Each system that's going to access resources on the REO must have its IQN typed into the REO and assigned to the logical drives it will access.

Although the REO has two Gigabit Ethernet ports, they must be set to different IP addresses, so they can't be set up for automatic load balancing or failover.

System configuration backups and software updates are simplified by the REO 4000's clever use of a USB flash memory key. Just move the key to any PC to back up its contents or upload a new software image. If you don't have a DHCP server, you can edit a text file on the USB key to set the management port's IP address.

Given the REO 4000's limited performance and expandability, it's best suited to the backup-and-restore applications for which it's designed.REO 4000, $17,500 (as configured). Overland Storage, (800) 729-8725, (858) 571-5555. www.overlandstorage.com

Howard Marks is founder and chief scientist of Networks Are Our Lives, a network design and consulting firm in Hoboken, N.J. Write to him at [email protected].

What are you going to do when you've got a huge wish list for storage but a budget that just might cover dinner for two at the local drive-through? Sure, everyone's got an eye on Fibre Channel, but the new iSCSI disk arrays are holding up against that technology with their relatively inexpensive answer to an enterprise SAN.

We tested iSCSI devices from Adaptec, Equalogic, FalconStor, Intransa, Promise Technology, Overland Storage and Snap Appliance, then rated them based on performance, functionality, management and price. With high marks for adaptability, FalconStor's product grabbed our Editor's Choice award.

We ran the open-source IOmeter benchmark to generate load and measure the performance of the iSCSI arrays. We tested each array using four servers (a Dell 1600SC with dual Xeon 2.4-GHz processors and 1 GB of memory using a QLogic 4010 iSCSI host bus adapter; two whitebox 2.4-GHz P4s, one with Alacritech HBAs, the other with the Microsoft Windows 2003 initiator and a low-cost Realtek-based gigabit card in addition to the Dell 1600SC; and a Compaq 1850 R with dual P3 550-MHz Xeons and 512 MB of RAM). The servers and iSCSI arrays were connected to an Extreme Networks Summit 7i Gigabit Ethernet switch.When possible, we configured the arrays with a single RAID 5 set and subdivided it into four iSCSI target disks. The Intransa array doesn't support RAID 5, and the Promise array doesn't support subdividing a RAID set, so we tested these systems with RAID 1 and RAID 10 logical drives, respectively.

In situations when an iSCSI array supported load balancing Ethernet bonding, we configured the array to make the best use of it. We manually load balanced systems with multiple Gigabit Ethernet connections that can't bond their ports by attaching two servers to each port. We configured IOmeter to use raw physical drives with a worker process for each processor. Each server accessed one iSCSI logical drive on the array.

The 64-KB and 2-MB transfer tests were sequential read and write tests, with the 2-MB test being a close analog of disk-to-disk backup applications. Our 512-byte IOPs test was also sequential access with single-sector requests. The Network Computing custom test used a mix of 512-byte, 2-KB and 64-KB request sizes with a 66/33 sequential/random access distribution.

R E V I E WiSCSI Targets

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