Which Drive Is Right for my Drobo?

Drobo gives you the flexibility to use a wide variety of drive types and capacities, but with many drive options to choose from, the process of getting the ideal drive is challenging. Not all drives are the same and if you do not choose the right one, your Drobo's performance may not meet your expectations.

Here are options you should consider when evaluating drives:

1. Grade – Quality is important when deciding what drive to use. If you will be actively using the drives most of the day in a business environment, for example, you should use enterprise-grade drives. Enterprise drives have higher MTBF (Mean Time Between Failures), which is a good thing when used with applications in continuous use.
2. RPM – When it comes to disk drive performance, the speed at which the disks spin is very important. Choose faster spinning drives (≥ 7200 RPM) for applications that can take advantage of higher-performance storage. For example, so-called "Green" (≤ 5600 RPM) drives have the lowest RPM rating and will be the slowest performing drives in a Drobo. For optimal performance, it's best not to mix 7200 RPM drives with slower drives. Also, it is not recommended to mix significantly different RPM speeds, such as 7200 RPM with 15,000 RPM in a Drobo B1200i.
3. Capacity – With Drobo, you can choose the capacity that you need today and expand with larger capacity drives in the future. Remember, with the disk redundancy in arrays like Drobo, one or more drives will be used to store parity data. Use the Drobo Capacity Calculator for specific information.
4. Form Factor – All 3.5" drives are compatible with Drobo's carrier-less design, requiring no tools or screws to install.
5. Cache – Most modern drives have a good amount of internal cache (32 or 64 MB), so this is not a critical deciding factor.
6. Interface – All Drobos use SATA (SATA II/III) drives, but the Drobo B1200i can also use SAS drives. The main difference is that SAS drives are dual-ported, enabling a high-availability architecture such as can be found in the B1200i.
7. Number of Drives – In arrays like Drobo, the more drives installed, the faster the performance. For example, if you are using a B800i in a VMware vSphere cluster, consider using 8 enterprise-grade drives instead of a smaller number such as 4. The same goes for the B1200i, where you should use 12 instead of 6.
8. Price – Despite the many other things to consider, often the #1 deciding factor when people purchase drives is price. Since performance, reliability, and energy efficiency are also key purchase criteria, price should not be the only consideration. Purchasing high-quality drives will give you a better storage experience by reducing the chance of having to replace or rebuild a drive—ultimately saving you money.

Desktop "Green" SATA Disk Drives

• Home or home office environments where reduced noise and energy efficiency are more important than performance
• Often the lowest-cost drive type
• Examples are WD Caviar Green and Seagate Barracuda Green

Desktop Performance SATA Disk Drives

• Home or small office environments where high-performance storage is required (≥ 7200 RPM)
• Often more reliable and recommended above "green" drives
• Examples are the WD Caviar Black and Seagate Barracuda XT

Enterprise "Green" SATA Disk Drives

• Small and medium-sized business environments in which reduced energy consumption and cooling requirements are more important than high performance
• The benefits of a "green" drive with enterprise reliability
• Good for file and backup servers that are not heavily exercised
• Example is the WD RE4-GP

Enterprise Performance SATA Disk Drives

• Small and medium-sized business environments that require reliable, high-performance storage that is affordable
• Good for server virtualization and business applications
• Examples are WD RE4 and Seagate Constellation ES (SATA)

Enterprise Performance SAS Disk Drives

• Small and medium-sized business environments that require reliable, high-performance storage
• Good for server virtualization and business applications
• Dual-ported for a high-availability architecture. The Drobo B1200i comes with 7200 RPM SAS drives. While the B1200i supports 15,000 RPM SAS drives, it is not recommended that you mix these two drive rotational speeds.
• Examples are WD RE SAS and Seagate Constellation ES (SAS)

Enterprise Performance SAS Solid State Drives (SSDs)

• Small and medium-sized business environments that require accelerated storage performance
• Good for high-density server virtualization and business-critical applications such as Microsoft Exchange
• Ideal when paired with Enterprise Performance SAS Disk Drives to create a multi-tier storage solution
• Examples are OCZ Talos, Seagate Pulsar, and Pliant Lightning.

Download a PDF with information about choosing the right drive for your Drobo.

SSDs for the Drobo B1200i

Similar to HDDs, there is a big difference between consumer and enterprise grade SSDs. Consider the following when selecting SSDs for your Drobo B1200i:

• SLC vs. MLC. Enterprise-grade SSDs used to be made exclusively of expensive SLC (single-level cell) flash, but many now use more cost-effective MLC (multi-level cell) flash. You can use either SLC or MLC as long as they are enterprise-grade SSDs.
• Overprovisioned space. Writing to an SSD is a time-consuming task if data already exists in the flash. This is called a “program/erase cycle.” Also, cells in the flash can fail over time, creating the demand for new cells. These are two reasons why SSDs are overprovisioned and have more memory than what's presented to the system. That overprovisioned space is used to maintain high levels of performance and to replace cells that have failed. Enterprise-grade SSDs often have a higher level of overprovisioned space, increasing performance and extending the life of the SSD.
• SSD controller. The controller inside the drive is often different for enterprise and consumer-grade SSDs. Enterprise drives are tuned more for extended use to handle more write cycles and use reclamation features such as TRIM and UNMAP* to be alerted and data removal by the system to optimize capacity and performance.
• SATA vs. SAS. Similar to HDDs, SSD drives are available with SATA or SAS connectivity. The Drobo B1200i will support both SATA and SAS drives, but enterprise-grade SSDs are only available with SAS connectivity.

For Drobo arrays for business, it is highly recommended that you use enterprise-grade SSDs and HDDs.

*In computing, TRIM and UNMAP commands allow systems to inform a solid-state drive (SSD) which blocks of data are no longer considered in use and can be wiped internally.