Whether it’s reviews of the latest 2.5” enterprise hard drives, a comparison of different capacity points within the same hard drive family or a shootout between 2.5” and 3.5” drives, we've already spent quite some time analyzing the move from 3.5" to 2.5" business-class storage. The most profound piece was probably the article Changing of the Guard: 2.5” Hard Drives in the Enterprise. But what is the best way for small and medium businesses to make the switch?
Swapping out functional drives for new disks doesn't happen very often, but there are a few situations in which it does make sense to transition over from 3.5” to 2.5” storage. Let’s keep in mind that all of this applies to traditional servers with specific storage requirements that revolve around I/O performance. Pure storage servers for nearline and offline storage, such as backup and archiving, will continue employing 3.5” in years to come, as the hard drive makers have been offering excellent high-capacity solutions for these application types.
One obvious setting in which you can easily migrate to 2.5” is the purchase of new servers or the complete replacement of older machines. New rackmount solutions based on 2.5” drives require a bit less power at comparable specs and allow for higher I/O density per rack space unit.
But what about individual hardware replacements? Individual component replacements usually make sense if there are increased capacities, better performance, or improved performance with newer products. In the server space, however, it is usually not easily possible to replace components because of validation issues. Many of the latest products haven't yet been tested and released for productive utilization in business environments.
A few hybrid products may help to bridge the transition period, because one fact is for sure: 2.5” will be the dominant form factor for mainstream servers and performance storage servers.
This option is well known and popular in the enthusiast community, which is quickly adopting SSDs and discovering that most desktop cases weren't designed for 2.5" disks. The idea is simple: basically you’d go for 2.5” SAS hard drives and install them into an existing 3.5” environment using available metal mounting frames. These can be obtained for very little money, and they attach on both sides of the hard drives in an effort to make the construction exactly as wide as a 3.5” drive.
However, while this approach works well in pedestal PCs and servers, where hard drives are installed into and integrated with the entire system, you will run into trouble once you try to do this in drive bays designed specifically for 3.5” drives and their easy replacement. The critical item here is the position of the SAS connectors. Mounting a 2.5” disk with installation frames usually results in dislocated SAS connectors. As these will most likely end up at a different position as it were the case with true 3.5” drives, you will probably not be able to actually connect your drives to the ports inside your drive cages.
This solution works great electrically and costs very little, but it is not applicable in mainstream server scenarios.
Can you see the different location of the SAS connectors? The aluminim frame around the drive has the connectors at the right position for 3.5” drives.
Electrically, any 2.5” drive works just fine in an installation frame, but mechanically you might end up with displaced connectors.
One perfect example for a 2.5” hard drive that was specifically designed to fit into 3.5” bays is the VelociRaptor drive by Western Digital. It is well-known among enthusiasts and a de-facto standard for high-end client PCs and even some workstations.
Not too long ago, WD decided to add such a 2.5”-to-3.5” drive to its VelociRaptor lineup to be able to serve the SMB and low-level enterprise markets as well. This step made sense, as deployments of the 2.5” VelociRaptor drives into 3.5” environments failed for the reasons explained on the previous page.
However, despite its ability to power demanding business systems these drives are technically not suitable for the enterprise storage segment, as they are only available with SATA 3Gb/s interfaces. In this case, interface speed isn’t a critical factor, but other SAS features like dual ports can be. The VelociRaptor appears interesting for large storage arrays, as it delivers an attractive cost per gigabyte at decent performance levels. However, you will lose all the flexibility that SAS infrastructures provide if you go this route. Please look at the article Next-Generation SAS: 6Gb/s Hits The Enerprise for more details on features and options.
There are only three companies left to compete in the 2.5” enterprise hard drive market: Hitachi, Seagate, and Toshiba. The latter finished its acquisition of Fujitsu’s storage division last year, making it the predominant player in this market segment. Our review of the Savvio 10K.4 and Toshiba’s MBF2600RC made clear that the Toshiba offering is slightly superior when it comes to performance, while Seagate makes up for this with more attractive MTBF ratings. Be that as it may, the MBF2600RC was quickly turned into a compliant 3.5” product for adoption of the latest hard drives into existing 3.5” environments.
The MBF260LRC is based on the aforementioned hard drive and is technically not different, with the exception of the surroundings on the outside. Not only does it come with a mounting frame for smooth deployment into 3.5” environment, but the product actually considers a few more details: connector position, cooling requirements (there are holes in the metal structure), and screw holes.
In the end, administrators and decision makers looking for modern SMB or entry-level enterprise storage might be interested in a transitional product like this one, as the MBF260LRC offers the latest 2.5” technology, performance, and power consumption for the 3.5” form factor, which all hard drive makers have told us is clearly on the retreat in the server mainstream.
Unfortunately, Toshiba treats the product seriously enough to forbid removing the drive from its installation frame. If you do, it voids your warranty.
Performance Segment
Decision makers looking to find the best solution for future server purchases have many reasons to relax. You will probably have to strictly consider the existing and projected performance requirements and work on the basis of worst-case scenarios. This means continuing on existing hardware, which should provide some time to carefully plan the next steps.
Although it will still take a few years, the future isn’t as bright for the hard drive anymore. Flash SSDs require a fraction of the power, and yet can deliver many times the I/O performance of conventional hard drives, or even hard drive arrays. I/O-intensive workloads are handled best by business-class flash-based SSDs if you can live with significantly smaller capacity points.
While SSDs still do not always provide reliable and especially predictable performance, future models will certainly be your top choice. A small array of a few flash SSDs will soon be perfectly capable of replacing an entire server rack, delivering more I/O performance, using much less power, and significantly reduced cooling cost. Take your time to plan thorough and to validate hardware carefully to exclude any issues SSDs might still have in stock today. Almost all SSD products available today are available in the 2.5” form factor. The only transitional product we've seen so far is OCZ's IBIS.
Capacity Segment
If you need lots of storage, then you have no option but to stay with 3.5” drives. Three terabyte capacity per drive was reached in the consumer space a few months ago and will soon be available for business and enterprise applications as well. Existing 3.5” SAS infrastructure is perfectly capable of working with these drives, although they are mostly based on SATA interfaces. You will even find power consumption and efficiency advantages, as 3.5” SATA, high-capacity drives are all based on 7200 RPM spindle speeds, requiring less cooling and delivering much increased capacity per space than 3.5” SAS drives.
Mainstream Segment
This article caters to the mainstream SMB and entry-level enterprise segment, in which the step into flash SSDs is oftentimes not needed, too costly, or too early, and where robust solutions are most important. It is definitely possible to replace aged drives with modern products with no effort and minimal risk.







