Compellent, iQstor, and Xiotech combine sophisticated enterprise capabilities with amazing ease
SAN storage systems continue to evolve quickly, with features trickling down from market leaders such as EMC and Hitachi Data Systems to midtier players. The three systems reviewed here, from Compellent, iQstor, and Xiotech, offer a surprising array of functionality including nearly every feature one might find in $250,000 enterprise-class systems except CAS (content addressed storage). Their impressive feature sets include 4Gbps FC (Fibre Channel) connectivity, iSCSI support, tiered storage, local and remote replication and snapshots, and even thin provisioning, boot from SAN, virtualization, and automatic expansion of volumes. Compellent even provides automatic migration of data from first- to second- or third-tier storage -- an ILM (information lifecycle management) tool that is usable without requiring a complex setup. Both Compellent and Xiotech offer monitoring and support services similar to those the tier-one storage vendors provide to large enterprises, allowing customers to respond proactively to projected failures.
[ See also: Fast guide to fancy SAN management ]
Great strides have also been made in ease of setup and administration. For instance, configuring a partition on the Compellent system to be remotely replicated on a second system hundreds of miles away was literally a two-minute job.
The three systems range in price (as tested) from $21,195 to $76,813, but with the price as configured it is difficult to make an apples-to-apples comparison. Capacity is not merely a matter of number of drives times drive capacity -- all of these systems support multiple tiers of storage, using 15K, 10K and 7.2K FC drives as well as the enormously less expensive and higher capacity (though slower and less reliable) SATA drives. Xiotech even offers an SSD (solid state disk) option that offers an extreme performance gain at a much higher cost per gigabyte -- a 6GB solid state module that fits into the same drive bays as the other disks.
System performance will greatly depend on a number of factors, including the types of drives installed, interface speeds, servers connected (operating system, drivers, HBAs installed, software in use), RAID levels of the partitions in use, number of drives in the partition, and the name of the administrator’s favorite cartoon character. Although the Xiotech system offers the ultimate in performance with SSD drives, the fact that a 6GB SSD drive is more expensive than a 750GB SATA drive will limit SSD use to the most performance-critical applications, such as database indices. Due to the varying numbers and types of drives, I did not attempt to measure performance across the systems, but instead focused on testing the features to ensure they performed as expected.
Compellent Storage Center
The Storage Center I received from Compellent came in two pieces: a Storage Center appliance and one 16-drive enclosure, which was equipped with eight 300GB 10K drives and eight 500GB 7.2K drives. The Storage Center can be used as a single controller for multiple enclosures, or dual controllers can be used for redundancy. Each enclosure supports three different classes of FC drives -- 15K, 10K, and 7.2K -- as well as SATA drives. The system as shipped came with 6.4TB of raw capacity, more than the others, and not at the highest price.
Setting up the Storage Center is a simple matter of configuring the IP address of the controller through a serial connection, which is usually performed by the Compellent tech during on-site installation. The wizards that help you automatically configure the system for use can safely be left in their default configurations, and virtually any setting you make can be changed later without having to reconfigure the volumes you create. This includes RAID levels, spare drives, number of tiers of storage, volume size, and more. The system automatically defines storage tiers based on the types of drives available; if more storage is added, additional tiers become available.
[ CompellentStorage Center 3.5 was selected for an InfoWorld Technology of the Year award. See the slideshow to view all winners in the storage category. ]
Compellent has clearly put considerable development effort into usability. Most features have setup wizards that make configuration a simple matter of entering the necessary information, or more often, selecting it from a list of available choices, and taking the default choices for most items. Thus, setting up and cloning boot from SAN configurations using the Server Instant Replay function, or setting up remote replication over IP to a second Storage Center in another location, are both simple operations. Remote replication includes deduplication and encryption, although not dedicated compression.
The automated data migration feature is unlike many ILM systems in that the administrator does not have to manually designate files to be moved or even create policies that move all files of a certain type or location. Instead, data that is infrequently accessed is moved automatically from the first-tier FC drives (10K or 15K) or second-tier FC drives (7.2K) to third-tier SATA-based storage, without requiring manual configuration or intervention by the administrator. Frequently accessed data is automatically kept in first-tier storage, and data that has been migrated is automatically moved back to first-tier when it begins to be used. Of course, the admin can designate partitions or even folders that will not be automatically migrated, if desired.
The instant replay function is another extremely useful feature of the Storage Center. An instant replay is a snapshot of the system at a given point in time. Because an instant replay uses only pointers to data, two replays use only as much storage as is required to store the pointers and copies of any files that have changed between the two snapshots. This amounts to data deduplication, and allows for virtually unlimited snapshots (unlimited by the software and limited physically only by disk capacity). Instant replay also supports VSS (Volume Shadow Copy Service) in Windows Server 2003, so Windows users can take advantage of the deduplication feature as well.
The same instant replay functionality can be used for servers. Once a boot volume is set up and the operating system is installed for a server, a second bootable volume can be created, and the only additional space used is that which stores the files that are different. For Linux this might amount to a few configuration files, and even for Windows it doesn’t amount to much except for the Windows swap file. This means that you could have several hundred servers booting from one main OS image, and each would maintain only the files that are different. It also means that rolling out patches and updates can be greatly simplified, since only the main image needs to be updated, and the others recloned. Unfortunately, there isn’t yet a way to push changes in the main image out to the clones.
The Compellent Storage Center offers superb ease of use and the widest feature set available in the middle range, without charging a premium price. The wizard-based configuration means that even administrators in small shops who don’t have time to go to storage administration training will be able to set up and use all the sophisticated features available. And the instant replay and automated migration features mean that you can get the best performance where needed and make full use of inexpensive SATA-based storage without any additional effort.
The iQstor iQ2880 storage system came all in one box, and it was simple to set up, using a preconfigured IP address and Web browser to enter the necessary network information. Oddly, the system wouldn’t initialize the RAID or complete storage configuration until an admin e-mail address for sending alerts was configured correctly, then it took about 35 minutes to initialize a 945GB RAID 5 volume. After one or more volumes are created, you assign a storage pool, which can be used for policy-based management, and then you create the virtual disks that are presented to the servers using the system. Virtual disks can easily be expanded without taking the corresponding physical volume offline.
The iQstor system offers less flexibility than the Compellent and Xiotech systems because it doesn't allow a RAID set to be changed or resized once created. The virtual disks in a RAID set can be changed, but not the underlying RAID level.
The system I tested included 15 73GB 4Gbps FC drives. The same enclosure supports a wide range of FC drives as well as SATA drives. The iQstor unit came in at the lowest price among the three systems tested. And though it also arrived with the lowest storage capacity, adding more drives or including higher capacity drives would not push the price from $21,195 to anywhere near the $50,000 or more of the other two. As with the Compellent and Xiotech systems, iQstor supports active-active controllers for full redundancy, and it's easy to add more FC or SATA enclosures to boost total capacity.
The iQstor offers a rich set of features that includes thin provisioning, snapshots, mirroring, replication, and virtualization. Plus, not only is it easy to expand existing volumes, but an automated capacity growth feature allows the system to use available, uncommitted storage to automatically expand volumes that are nearing full capacity.
iQstor includes an agent that makes it easy to create point-in-time snapshots of open Exchange, Oracle, and SQL Server databases. The agents pause the database long enough for the iQstor to take simultaneous “group snapshots” of all active data volumes, ensuring that all open records are correctly copied. The snapshots can then be used to make tape backups or remote replicas without having to shut down the database for the duration of the backup.
As with the other two systems reviewed here, snapshots use pointers to accelerate snaps and save disk space, requiring just 10 percent to 20 percent of the space required for a full copy of a volume. The number of snapshots is not unlimited, but the limit of 126 snapshots per volume should be enough for most people.
The iQstor iQ2880 does not offer every bell and whistle of the Compellent and Xiotech SANs, and it takes a bit more effort to set up, but it offers great performance, scales to 180TB with SATA drives, and starts at less than half the price of the other two systems. It is an excellent way to go if you don’t anticipate the need for the fancy features.
Xiotech Magnitude 3D 3000eThe Magnitude 3D 3000e Storage System I tested consisted of several separate pieces: the Icon management appliance, one controller, one shelf of drives, and the TimeScale appliance that manages asynchronous replication, heterogeneous replication, and CDP (continuous data protection). The shelf included eight 73GB FC drives and eight 146GB FC drives. The Icon appliance is used to manage the controller. It seems a bit much to use a separate management appliance if you have only one controller, but it will manage many controllers just as easily.
The TimeScale appliance offloads compression and data encryption over the WAN link, removing that load from the controller and allowing replication between multiple controllers with ease. It also handles heterogeneous replication, allowing replication between storage systems from different vendors, whether SAN-attached or server attached, and provides continuous data protection, a journal-based form of replication that goes beyond the capabilities of standard synchronous or asynchronous replication.
On-site installation support is included, so most administrators will probably not see much of the installation process, which is probably for the best, since the combination of four or more separate pieces of hardware does introduce some complexity. The Icon interface for configuring volumes and other functions such as mirroring and synchronous replication is straightforward. It's not as wizardly as the Compellent system, but easy enough to work your way through. Figuring out whether to use the Icon interface or the TimeScale interface to set up some things like remote replication can also be a puzzle, although one you’ll quickly solve.
The Magnitude 3D supports ILM-style data migration through host-based software, which uses agents on each server to identify data that can be migrated from tier one to tier two or three. This is not as transparent as data migration in Compellent, which is handled in the controller with no server agents or additional load on the servers required. Nevertheless Xiotech provides some of the same functionality, albeit with more setup required.
The TimeScale appliance enables a number of features not available from Compellent. It provides compression, encryption, and deduplication of data sent over the WAN link, which both secures transmitted data and optimizes the use of the link. TimeScale can replicate data to other systems from other storage vendors, even allowing the use of server-attached storage. This means that a single TimeScale box can facilitate replication across the enterprise, between a widely disparate variety of storage systems. TimeScale also supports bandwidth limiting by connection, allowing the administrator to control both the amount of bandwidth consumed by remote replication or CDP and also the amount of server utilization for local replication. Server utilization can be a significant factor, because heterogeneous replication routes data through the server that the storage is attached to, rather than bypassing the server and routing data from one SAN device to another. This is the only way to make use of non-SAN storage, but it can introduce fairly heavy loads on the server, depending on the amount of data being replicated.
Creating asynchronous replicas (on a second Xiotech SAN system) over the WAN using the TimeScale appliance is straightforward and fairly simple, although not quite as simple as the five-click process in Compellent. Given the additional complexity introduced by enabling the use of other SAN devices and server-attached storage, this is not unexpected, and in fact it makes the smoothness of the Xiotech process all the more admirable.
TimeScale also allows the administrator to schedule and create an unlimited number of snapshots for data or system recovery, using either virtual snapshots to reduce the storage footprint or full replicas of the original data. Snapshots can be one to many, many to one, or many to many, allowing multiple snapshots to be created in different places from a single original, or allowing multiple originals to be consolidated into a single storage system.
The Xiotech system with the TimeScale appliance offers a couple of features not available from Compellent, including the SSD drives and replication and mirroring with heterogeneous devices. It doesn’t have hardware-based ILM, and it's not quite as easy to use as the Compellent system, but it's an excellent choice for administrators aiming to reuse existing storage assets.
The fat middle
All three of the systems reviewed here will provide excellent service in a small to midlevel enterprise environment. They are inexpensive enough to be good starter systems, yet expandable enough to grow with a company’s data needs. And all combine good usability and strong performance.
The iQstor iQ2880 has a more limited feature set than the other two, but still enough for most purposes, and it comes at a very low price. The Xiotech Magnitude 3D system offers sophisticated features at a reasonable price, including the highest possible performance (thanks to the solid state disk option) and excellent replication functions that support any SAN or server attached storage, even from other vendors.
The Compellent Storage Center offers the greatest ease of use, as well as automated data migration capabilities, at a great price. In fact, Compellent's level of maturity, both in feature set and ease of use, places it alone at the pinnacle of midrange systems and even compares favorably with top-tier systems. That said, if you don't need automated data migration, the iQstor is the most affordable way to start. And Xiotech should get a close look from any shop looking for a SAN that plays well with existing storage.
Overall Score (100%)
|Compellent Storage Center 3.5||9.0||9.0||8.0||9.0||10.0||9.0|
|Xiotech Magnitude 3D 3000e||9.0||8.0||9.0||9.0||9.0||9.0|
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