Hey guys, I know this thread isn't the most active place on the internets but I'm hoping maybe a storage networking guru can help me out. I'm troubleshooting poor performance on our iSCSI SAN and seeing some interesting IOmeter results:
Array: FreeNAS 27 SATA disk array 2x 1Gb links
| Access Specification Name | IOps | MBps | Latency(ms) |
| Max Throughput-100%Read | 3563.99 | 111.37 | 16.80 |
| RealLife-60%Rand-65%Read | 984.89 | 7.69 | 60.35 |
| Max Throughput-50%Read | 5800.14 | 181.25 | 10.11 |
| Random-8k-70%Read | 1692.67 | 13.22 | 35.09 |
Now, looking past these fairly mediocre results - one thing that's come up consistently is that the 100% random 8K 70% Read tests is consistently faster than the RealLife test, sometimes up to 2x as "fast" and considerably less latency (although both are bad, I know). In my mind I'm thinking that the 100% randomness should result in slower performance... I'm wondering if this is a symptom of some sort of misconfig on our networking gear. I've isolated it to our iSCSI "core", which is a stack of four PowerConnect 8024s. If i isolated this array to a single switch in the stack and run the tests directly from my laptop these are the results (I think I'm hitting some bottlenecks related to the laptop NIC):
| Access Specification Name | IOps | MBps | Latency(ms) |
| Max Throughput-100%Read | 1798.61 | 56.21 | 25.48 |
| RealLife-60%Rand-65%Read | 5447.46 | 42.56 | 6.20 |
| Max Throughput-50%Read | 1757.25 | 54.91 | 21.81 |
| Random-8k-70%Read | 5245.12 | 40.98 | 6.10 |
Anyway, I've reviewed the 8024s config and they're to Dell's recommended best practices (jumbos, flow control, unicast storm control disabled). Nothing looks obviously wrong in the stack, CPU/mem utilization is fine, no stackport errors, etc etc.
Someone want to throw an idea my way? I'm out of ideas. Thanks!