There are a few explanations for poor performance on DDP and for the vast majority of cases the causes are external – network settings, for example, are a common external cause of problems. However, DDP can encounter other difficulties that may negatively affect its performance.
For this reason, we recommend you test your DDP by running the pvspeed utility that is built in to the DDP web GUI on the Utility page. This utility will test each raid set of your DDP and display the current “Bandwidth” you can get for each of them. All raid sets should show similar results, so if you have an anomalous result where a particular raid set shows a very different number than the others, you will know that somewhere, something is not right.
The following picture shows how the results should look:
The total Bandwidth of is over 4GB/s as we have 6 Raid sets x 8 drives in (we use Raid 5 or Raid 6), so model tested above is DDP48D – with 48 SATA drives.
The following picture shows what abnormal results for one of the raid set might look like:
Generally when this happens it means that one drive of that particular raid set is about to fail. It might be causing “timeouts” and you can check this out easily by taking a look at the raid card logs and each raid set status (also integrated in DDP Web GUI). You can also check the blinking light during the speed tests or even during regular operation; you should be able to see if the drive light is out of sync while tests are performed.
If no error can been seen in the logs and each raid sets status is displayed as normal, we recommend you run a “Volume Check” to make sure that all drives are functioning with no errors.
If the Volume Check finishes without any errors, then the raid card itself might be faulty.
If you suspect this to be the case, then please contact our team.
Of course, if you set up email notification and schedule regular Volume Checks you should be able to keep a close eye on performance.
On the Utility page, there is also “Netstat” button where you can monitor if there is any “retransmission” of the packets. If there are, check your network settings such as MTU, switch etc.