I’ve always wondered how much of a performance benefit there is when using SSDs in a RAID config. How fast in the NV cache on the PERC card? Is there a major write performance difference with 4 SSDs in a RAID 10 vs. a single SSD? What about reads? Or random reads? How about a different in time when cloning a VM?
To answer these questions and more, I used a single PowerEdge R630 server with a PERC H730P controller and 4 Samsung EVO 850 SSDs and changed one variable at a time (cache mode or RAID level). Here’s how cache mode change is named:
- Caching = Read-Ahead, Write-Back, Disk Cache Policy Enabled
- Typical Caching = Read-Ahead, Write-Through, Disk Cache Policy Enabled
- No Read caching = No Read Ahead, Write-Through, Disk Cache Policy Enabled
- Minimal caching = No Read Ahead, Write-Through, Disk Cache Policy disabled
Different RAID levels included:
- RAID 0 – 4 drives
- RAID 10 – 4 drives
- RAID 0 – 1 drive
The speed tests used for this are:
- Anvil
- HD Tune
- Performance Test 8
- CrystalDiskMark
- VMware (VMDK clone time)
And here are the results (scroll to the right to see it all):
| Test | RAID 0 – Caching | RAID 0 – Typical Caching | RAID 0 – No Read-Caching | RAID 0 – Minimal caching | RAID 10 – Caching | RAID 10 – Typical Caching | RAID 10 – No Read-Caching | RAID 10 – Minimal caching | Single – Caching | Single – Minimal caching |
| CrystalDisk – Sequential Read Q32 | 5721 | 2066 | 2054 | 2066 | 5713 | 2003 | 2003 | 1885 | 5723 | 547.2 |
| CrystalDisk – 4K Q32 Read | 467.2 | 530.9 | 675.1 | 687.7 | 454.5 | 515.1 | 598.9 | 580.8 | 462.6 | 275.9 |
| CrystalDisk – Sequential Read | 3555 | 1634 | 1629 | 1635 | 3533 | 1071 | 1073 | 821.9 | 3117 | 520.3 |
| CrystalDisk – 4K Read | 109.7 | 32.87 | 35.65 | 35.32 | 109.7 | 37.54 | 38.21 | 32.76 | 109.3 | 42.13 |
| CrystalDisk – Sequential Write Q32 | 6833 | 321.7 | 322 | 316.3 | 6836 | 245.2 | 244.8 | 110.3 | 6836 | 223.8 |
| CrystalDisk – 4K Q32 Write | 463.4 | 19.44 | 20.02 | 20.1 | 135.7 | 15.97 | 15.91 | 10.29 | 451.5 | 22.87 |
| CrystalDisk – Sequential Write | 4056 | 84.94 | 85.77 | 84.52 | 363.5 | 59.98 | 39.64 | 33.97 | 3902 | 139.9 |
| CrystalDisk – 4K Write | 104.4 | 1.129 | 1.14 | 1.129 | 30.21 | 0.633 | 0.621 | 0.7 | 104.7 | 1.178 |
| HD Tune – Minimum Read | 978.5 | 945.3 | 359.4 | 15.5 | 958.1 | 820.8 | 376 | 374.3 | 339.4 | 357.7 |
| HD Tune – Maximum Read | 3083.2 | 3095.9 | 3092 | 3041.4 | 3093.1 | 3135.8 | 3044.7 | 3114.2 | 3009.7 | 3041 |
| HD Tune – Average Read | 1645.9 | 1654 | 1273.2 | 1262.8 | 1638.6 | 1639.1 | 1267 | 1282.5 | 1198.9 | 1193 |
| HD Tune – Access Time Read | 0.086 | 0.087 | 0.081 | 0.081 | 0.083 | 0.086 | 0.085 | 0.082 | 0.085 | 0.082 |
| HD Tune – Burst Rate Read | 212.9 | 213.7 | 221.6 | 220.7 | 226.2 | 213 | 226.7 | 279.6 | 224.9 | 236.5 |
| HD Tune – 4K Read | 43.351 | 43.352 | 45.639 | 44.274 | 44.622 | 41.534 | 44.244 | 44.247 | 43.074 | 25.992 |
| PT8 – Sequential Read | 2826 | 2170 | 1210 | 1040 | 2780 | 1531 | 1393 | 1349 | 2749 | 497 |
| PT8 – Sequential Write | 2714 | 77 | 82.7 | 83.4 | 2774 | 25.3 | 27.1 | 32.4 | 2618 | 74.1 |
| PT8 – Random Seek + RW | 2461 | 132.1 | 100.4 | 110.9 | 2540 | 50.1 | 53.6 | 50.5 | 2361 | 110.9 |
| Anvil – Sequential Read 4 MB | 3282.05 | 1726.81 | 1641.03 | 1682.83 | 3864.15 | 1381.92 | 1458.69 | 1172.3 | 4231.4 | 501.1 |
| Anvil – Sequential Read 4K | 72.88 | 29.42 | 33.36 | 33.67 | 77.58 | 30.77 | 29.77 | 27.35 | 88.56 | 35.47 |
| Anvil – Read 4K QD4 | 212.61 | 100.33 | 108.73 | 107.13 | 233.48 | 104.27 | 105.05 | 89.38 | 244.01 | 105.43 |
| Anvil – Read 4K QD16 | 370.83 | 340.83 | 386.39 | 386.21 | 374.12 | 309.96 | 342.07 | 312.05 | 387.46 | 249.09 |
| Anvil – Read 32K | 423.15 | 163.03 | 168.86 | 167.95 | 606.15 | 194.05 | 193.05 | 168.3 | 637.76 | 165.75 |
| Anvil – Read 128K | 1091.11 | 428 | 434.64 | 435.97 | 1495.05 | 512.5 | 513.79 | 431.12 | 1549.34 | 309.36 |
| Anvil – Sequential Write 4 MB | 1261.08 | 149.53 | 190.26 | 201.97 | 713.09 | 149.88 | 140.85 | 69.24 | 434.82 | 176.46 |
| Anvil – Write 4K | 93 | 1.08 | 1.07 | 1.07 | 96.04 | 0.99 | 0.99 | 0.58 | 97.19 | 1.11 |
| Anvil – Write 4K QD4 | 192.62 | 3.18 | 3.19 | 3.2 | 230.23 | 2.45 | 2.44 | 1.42 | 232.22 | 2.55 |
| Anvil – Write 4K QD16 | 283.68 | 9.93 | 10.05 | 10.1 | 396.82 | 8.09 | 8.12 | 4.09 | 398.49 | 9.31 |
| VMDK Clone Time (seconds) | 81 | 187 | 184 | 186 | 250 | 636 | 629 | 591 | 411 | 442 |
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