As an Amazon Associate I earn from qualifying purchases @AMAZON
Drobo 5D Read/Write Performance Across Capacity
Related: backup, diglloydTools, DiskTester, hard drive, RAID, storage, Thunderbolt
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.

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 https://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
Incidentals
The five volume icons, etc.


Always exclude volumes from Spotlight before testing.
