Before we started in on our normal tests, we took a look at how the performance scaled from 1 to 24 drives. This should show us whether the drives or the RAID adapter is limiting our performance. This is where the fun starts. No matter how fast an individual component is in the system, there is always a bottleneck. Whether it be the storage device, PCIe bus interface or the ROC, the bottleneck in these large systems is always a moving target. This test should show us where we are limited.
We took a look at sequential and random performance, starting with a single drive until we reached 24. We limited the test time to only 5 minutes for each test and limited the LBAs to 50% of the total capacity.
For all operations, the system scaled almost linearly until we reached the maximum performance of the ASR-72405. Random read operations required only 8 drives to reach over 550,000 IOPS, while write operations required nearly 21 drives to reach the same levels.
Sequential performance was nearly identical for both reads and writes. We saturated the system performance after 13 drives.
After we finished the drive scaling tests, we started to notice something interesting. When tested across all LBAs, we observed significantly lower performance in our random tests. There was no difference with sequential tests, which was expected.
Once we passed the 50% mark for LBAs tested, the performance dropped to 370,000 for both read and write operations. Since we normally test 100% of the LBAs, the tests throughout the rest of the review will reflect that.
From here, we can draw a couple of conclusions. The first is that even with 24 native ports, the Adaptec ASR-72405 is clearly outmatched by the 24 SMART Optimus SSDs. When you take into account that for full LBA testing the ASR-72405 is limited to 370,000 IOPS, the best option for maximizing performance and cost is the ASR-71605, the 16 port version.
Now that we know that the ASR-72405 is the bottleneck, we wondered what would happen if we removed it? We were able to procure a second ASR-72405 and split the drives evenly across the two. You will notice that many of the subsequent performance tests include the results where we used two ASR-72405s. Those results are based on full LBA testing, but we wanted to see what we could hit with both cards, using 50% of the LBAs. Here’s what we saw.
1 million input/output operations per second…
That really wasn’t that hard. All you need is two RAID adapters and 24 SSDs, which may sound like a lot, but considering existing solutions that claim 1M IOPS, it is actually a reasonable proposition. Now that we got that out of the way, lets move on to some more meaningful tests.