Data Robotics Drobo S Review
Test System and ATTO Disk Benchmark Testing
Our Test Methodologies: The Drobo S and comparison devices were tested as external volumes attached to our HP Pavilion m9550f testbed system (2.5GHz Intel Core 2 Quad Q9300; 8GB PC2-6400 DDR2 SDRAM; 1TB NTFS 7,200RPM SATA 3Gb/Sec hard drive; ATI Radeon HD 4850 512MB, Windows 7 Ultimate 64-bit). We tested each device using its fastest (eSATA) and its slowest (USB 2.0) connection interfaces. All the devices were tested using 2TB Seagate Barracuda XT hard drives, formatted as a single NTFS volume, using a GUID Partition Table (GPT). We also tested each device in two modes: using its most aggressive and its least aggressive tolerance settings.
As our m9550f testbed does not have native eSATA support, we used an IOGear GICe711S3 PCI Express card. We didn't conduct formal performance testing with any of the devices' FireWire connections, but we did do anecdotal compatibility testing with those devices that had FireWire 400 and 800 connections, using a Vantec FireWire 400/800 PCI Host Card (UGT-FW100) in our testbed.
Networking, Windows firewall, automatic updates, and screen savers were all disabled before testing. With all test runs, we rebooted the system and waited several minutes for drive activity to settle before invoking a test. All tests were run multiple times (no less than three times, and often more) and we used the best (non-anomalous) score available.
We compared the Drobo S against the two other multi-drive DAS devices: the Vantec NexStar MX (NST-400MX-SR) and the Promise SmartStor DS4600. The NexStar MX is an inexpensive (around $100) two-bay device; with eSATA and USB 2.0 ports; and support for RAID 0, RAID 1, and JBOD. Even though the NexStar MX isn't in the same class as the Drobo S, we included it because we wanted to show the relative performance between the Drobo S and a much less-expensive alternative. If you don't need the storage capacity or feature set of the Drobo S, there are much less-expensive options available, such as the NexStar MX. The DS4600 represents a more apples-to-apples comparison with the Drobo S: It is a four-bay DAS device; with eSATA, USB 2.0, FireWire 400, and FireWire 800 ports; and support for RAID 0, RAID 1, RAID 5, and RAID 10. The DS4600 sells for around $300.
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ATTO is a disk benchmark that measures transfers across a specific volume length, measuring raw transfer rates for both reads and writes. The charts below reflects a best-case performance scenario, using 8,192KB (8MB) transfer sizes over a total volume length of 256MB. Smaller transfer sizes in this test exhibit lower peak performance than what is reflected in the graphs below.
The most glaringly obvious and fully expected observation here is that the eSATA transfer rates of all the devices far exceed that of their USB 2.0 speeds. The maximum theoretical data transfer rate for USB 2.0 is about 60MB/Sec, which is notably slower than the actual transfer rate capabilities of many hard drives--meaning that the USB 2.0 interface itself will be the bottleneck in most instances. The eSATA interface we used has a theoretical data transfer rate of about 375MB/Sec, which is faster than any data transfer rate we've ever measured for a SATA hard drive--or even standard SATA SSDs currently, for that matter. For instance, the 2TB Seagate Barracuda XT drives we used in all the devices here, scored a write speed of 143.8MB/Sec and a read speed of 147.5MB/Sec on the ATTO test in our recent 2TB hard drive roundup. If your system has an eSATA interface, you'll see marked higher transfer speeds over USB 2.0. Both the Drobo S and the SmarStor DS4600 also support FireWire 800, which while not as speedy as eSATA, is still faster than USB 2.0.
Using the eSATA interface, the SmartStor DS4600 was the disputed performance winner on the ATTO test by a large margin. It also bears mentioning that the SmartStor DS4600 only suffered a small performance penalty going from RAID 0 mode to RAID 10 mode. On the other hand, the Vantec NexStar MX saw a noticeable drop in write performance going from RAID 0 mode to it's more robust RAID 1 setting, though its read speed stayed steady in both RAID modes. We also saw a write speed performance drop with the Drobo S when going from single-drive protection mode to Dual Disk Redundancy mode--the Drobo S's write speed of 58,996KB/Sec when using dual disk protection was the slowest of the group when using eSATA. Whether using single- or dual-disk protection, the Drobo S also had the slowest eSATA read speeds of the bunch--although, curiously we actually saw faster read speeds from the Drobo S using dual-disk protection than with single-disk protection.
The results played out similarly when using the USB 2.0 interface, with the SmartStor DS4600 still taking the read and write performance leads--although this time, the Drobo S was not far behind the DS4600. You'll also notice that the SmartStor DS4600 RAID 0 and RAID 10 scores are virtually identical--and the same can be said for the Drobo S's single and dual-disk protection scores as well. This tells us that the USB 2.0 interface's limitations are kicking in before the full performance capabilities of the devices can be achieved. As we saw with the eSATA results, the NexStar MX puts in slower performance when going from RAID 0 to RAID 1 mode. When it comes to using USB 2.0, the NexStar MX has the slowest write and read performance.
Using the eSATA interface, the SmartStor DS4600 was the disputed performance winner on the ATTO test by a large margin. It also bears mentioning that the SmartStor DS4600 only suffered a small performance penalty going from RAID 0 mode to RAID 10 mode. On the other hand, the Vantec NexStar MX saw a noticeable drop in write performance going from RAID 0 mode to it's more robust RAID 1 setting, though its read speed stayed steady in both RAID modes. We also saw a write speed performance drop with the Drobo S when going from single-drive protection mode to Dual Disk Redundancy mode--the Drobo S's write speed of 58,996KB/Sec when using dual disk protection was the slowest of the group when using eSATA. Whether using single- or dual-disk protection, the Drobo S also had the slowest eSATA read speeds of the bunch--although, curiously we actually saw faster read speeds from the Drobo S using dual-disk protection than with single-disk protection.
The results played out similarly when using the USB 2.0 interface, with the SmartStor DS4600 still taking the read and write performance leads--although this time, the Drobo S was not far behind the DS4600. You'll also notice that the SmartStor DS4600 RAID 0 and RAID 10 scores are virtually identical--and the same can be said for the Drobo S's single and dual-disk protection scores as well. This tells us that the USB 2.0 interface's limitations are kicking in before the full performance capabilities of the devices can be achieved. As we saw with the eSATA results, the NexStar MX puts in slower performance when going from RAID 0 to RAID 1 mode. When it comes to using USB 2.0, the NexStar MX has the slowest write and read performance.
