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Drobo 5D Read/Write Performance Across Capacity

B&H Photo supplied the Data Robotics Drobo 5D for testing, along with five Hitachi 4TB hard drives.

Testing was on the fast 2.7 GHz MacBook Pro with Retina display via Thunderbolt.

Background

With a plain hard drive, performance drops off across the drive due to a fixed data density passing by the heads as per C = πD. See Why You Need More Space Than You You Need. When there is overhead of some kind, the speed will be throttled and thus the across-the-capacity performance will be relatively constant, suppressing the usual pattern.

Performance across the capacity

To test the Drobo 5D performance across its capacity, five equal-sized partitions were made to occupy the entire capacity; each was tested using:

'disktester run-sequential --iterations 10 --test-size 8GB'.

The test gives insight into the performance across the entire ~15GB capacity by testing each of the five volumes in turn.

The Drobo 5D throttles write speed to moderately faster than a single hard drive, and moderately faster than two hard drives for reads. The data suggest that the RAID-5 computations (for parity) are done in some serialized or semi-serialized manner, which thus limits speed to that of 1-2 drives.

For a point of reference, the graph below includes a RAID-0 stripe of two Toshiba 3TB hard drives on the Mac Pro internal SATA ports. The stripe will decline in performance over its capacity as expected, while the 5-drive Drobo should maintain the figures seen below.

Sequential read and write speed (DiskTester) across entire capacity
Drobo 5D via Thunderbolt on 2.7 GHz MacBook Pro Retina

Area test

A confirming test on the entire Drobo 5D as a single volume was done using disktester run-area-test, showing very similar result to the graph above.

llcR:DIGLLOYD lloyd$ disktester run-area-test --iterations 5 --test-size 8G d5d
DiskTester 2.2 64-bit, diglloydTools 2.2.0, 2012-12-15 18:05
Copyright 2006-2012 DIGLLOYD INC. All Rights Reserved
Use of this software requires a license. See http://macperformanceguide.com/Software-License.html
OS X 10.8.2, 8 CPU cores, 16384MB memory
Friday, February 1, 2013 14:49:10  Pacific Standard Time
disktester run-area-test --iterations 5 --test-size 8G d5d
Allocating maximum size contiguous file on "d5d" (16.0TB)...16.0TB (99.9% of volume size)
TEMP FILE: /Volumes/d5d/disktester-test/DiskTester-Temporary-Test-File
Using test size of 8GB, 4MB at a time, across a 16.0TB test file.
Testing at: 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%
Friday, February 1, 2013 14:49:10  Pacific Standard Time, volume "d5d" (16.0TB)  
---------------- Write Details for "d5d" (8GB/4MB, 5 iterations) ---------------
Area (16.0TB)	Slowest	Median	Fastest	Average	Range
0%    	  224  	  228 	  231  	  228  	  7.5
10%    	  221  	  228 	  228  	  226  	  6.9
20%    	  218  	  226 	  227  	  225  	  9.4
30%    	  218  	  229 	  230  	  227  	 11.9
40%    	  202  	  230 	  231  	  225  	 29.4
50%    	  195  	  229 	  230  	  222  	 34.5
60%    	  194  	  229 	  231  	  223  	 36.5
70%    	  195  	  227 	  230  	  221  	 34.7
80%    	  194  	  227 	  231  	  221  	 36.5
90%    	  192  	  226 	  228  	  219  	 36.3
100%    	  193  	  228 	  230  	  221  	 36.4
---------------- Read Details for "d5d" (8GB/4MB, 5 iterations) ----------------
Area (16.0TB)	Slowest	Median	Fastest	Average	Range
0%    	  294  	  301 	  313  	  304  	 18.9
10%    	  315  	  321 	  331  	  323  	 16.8
20%    	  319  	  335 	  360  	  337  	 41.0
30%    	  318  	  328 	  346  	  328  	 28.1
40%    	  310  	  327 	  335  	  325  	 25.0
50%    	  310  	  331 	  348  	  331  	 38.1
60%    	  315  	  325 	  335  	  324  	 19.8
70%    	  315  	  333 	  350  	  332  	 35.2
80%    	  312  	  316 	  352  	  328  	 39.7
90%    	  291  	  340 	  343  	  326  	 51.9
100%    	  314  	  325 	  340  	  326  	 26.2
------------------ Averages for "d5d" (8GB/4MB, 5 iterations) ------------------
Area (16.0TB)	Write MB/sec	Read MB/sec
0%    	     228    	    304    
10%    	     226    	    323    
20%    	     225    	    337    
30%    	     227    	    328    
40%    	     225    	    325    
50%    	     222    	    331    
60%    	     223    	    324    
70%    	     221    	    332    
80%    	     221    	    328    
90%    	     219    	    326    
100%    	     221    	    326    
Average write speed across the volume: 223MB/sec
Average read speed across the volume: 326MB/sec
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Incidentals

The five volume icons, etc.

Five partitions of equal size on the Drobo 5D
Five partitions of equal size on the Drobo 5D

Always exclude volumes from Spotlight before testing.

All tests exclude test volumes from Spotlight indexing
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