PCI-E Link Width Improperly Negotiated

Problem

Currently shipping ioDrives are x4 PCI Express cards. The ioDrive Duo is an x8 PCI Express card.* If the system is having difficulties talking to the ioDrive, the system might talk to the ioDrive using only an x1 link, which has 1/4th the performance of an x4 link.

Solution

Use the fio-pci-check utility to check for this problem and to report any issues with link width.

Below is an example of PCI link width errors captured on a system with an ioDrive.

Root Bridge PCIe 250 MB/sec



 Bridge 00:01.00 (01-01)

 Needed 250 MB/sec Avail 250 MB/sec

 Current control settings: 0x0000

 Correctable Error Reporting: disabled, enabling now

 Non-Fatal Error Reporting: disabled, enabling now

 Fatal Error Reporting: disabled, enabling now

 Unsupported Request Reporting: disabled, enabling now

 Current status: 0x0000

 Correctable Error(s): None

 Non-Fatal Error(s): None

 Fatal Error(s): None

 Unsupported Type(s): None

 Current link_capabilities: 0x02012501

 Maximum link speed: 2.5 Gb/s

 Maximum link width: 16 lanes

 Current link_capabilities: 0x00001011

 Link speed: 2.5 Gb/s

 Link width is 1 lanes



 ioDrive 01:00.0 Firmware 14071

Figure 15 – Bandwidth error, x1 link negotiated with insufficient bandwidth (250 MB/s)

* Assuming PCI-E 1.1 specification