As an Amazon Associate I earn from qualifying purchases @AMAZON
RAID 1+0: Striping a Pair of Mirrors for Fault Tolerance
Related: diglloydTools, DiskTester, fault tolerance, Other World Computing, OWC Mercury Elite Pro, RAID, storage, Thunderbolt, USB
See the overview of the OWC Mercury Elite Pro Dual.
With two OWC Mercury Elite Pro Dual units on hand (briefly), a thought arose: daisy chained and using one Thunderbolt port, how about an easy-as-pie fault tolerant setup?
Fault tolerance
Some workflow environments have a “cannot be down” operating principle. Examples might include a service bureau, where jobs have to be finished on some deadline (e.g., by 5PM).
Fault tolerance means some degree of failure can be tolerated with no data loss and no loss of functionality. A RAID-1 mirror is the most basic kind of fault tolerance, but sometimes more performance is desired. Thus, a RAID-0 stripe of RAID-1 mirrors comes to mind.
With a pair of the OWC Mercury Elite Pro Dual units, it is easy to make a striped pair of mirrors (RAID 1+0), which achieves both high performance and fault tolerance for critical workflow environments:
- Configure each OWC Mercury Elite Pro Dual unit to Mirror mode.
- Make a RAID-0 stripe of the two units.
With this setup, one drive can fail in each unit with no data loss and continued functionality (replaced the failed drive ASAP).
Performance
These two units were mismatched but were what was on hand; one had dual 4TB drives and the other had dual 3TB drives. Faster results might be expected from matched and/or faster hard drives, not that these results are at all slow!
Testing performed with the DiskTester fill-volume command. DiskTester is part of diglloydTools. The command line version was used here.
llcR:~ lloyd$ disktester run-sequential -i 10 r1+0
DiskTester 2.2 64-bit, diglloydTools 2.2.0, 2012-12-15 18:05
OS X 10.9.1, 8 CPU cores, 16384MB memory
Allocating maximum size contiguous file on "r1+0" (2TB)...1.99TB (99.5% of volume size)
Using test size of 4GB, 4MB at a time at start (0%), within a 1.99TB test file.
...elided...
Monday, December 30, 2013 at 20:37:25 Pacific Standard Time, volume "r1+0" (2TB)
--------------- Averages for "r1+0" (4GB/4MB, 10 iterations) ---------------
Iteration Write MB/sec Read MB/sec
1 318 318
2 302 317
3 316 317
4 316 317
5 319 316
6 319 316
7 318 316
8 318 317
9 316 318
10 317 319
Slowest 302 316
Fastest 319 319
Average 316 317
Median 317 317
Range 17.2 3.22
Command "run-sequential" executed in 261.02 seconds on Monday, December 30, 2013 at 20:41:46 Pacific Standard Time


Apple 16.2" MacBook Pro with M1 Max Chip (Late 2021, Space Gray)
SAVE $1100