An R740 with a PERC H730p is extremely slow even though its built-in hardware tests pass. It can create a RAID 10 array, but performance is still terrible with other known-good drives and in both RAID and HBA modes.
A Windows install took hours, and Linux appeared to report repeated drive resets. Could the controller be failing without showing an obvious fault, or should I be looking at the backplane or something else?
The controller is a reasonable suspect, but the backplane and SAS cables are still in the path too. A hardware test passing doesn't rule out an intermittent connection.
Power the server down and inspect and reseat the controller and its cables. Look for damaged connectors or corrosion. If you've got compatible spares, swap one component at a time so you can tell what changed. Start with the cables or controller, then consider the backplane.
Check the controller cache battery and its reported status in iDRAC and the PERC configuration. A cache issue can hurt write performance, though it doesn't neatly explain drive resets or the same severe symptoms in HBA mode.
u316+paperclip_8:
Neither interface shows a battery warning, and switching between write-through and forced write-back didn't seem to change the behavior.
I'd chase down the exact Linux reset message before buying parts. Check the system event log and IPMI sensor data as well, even if the usual controller screens look clean. The reset details might help narrow down which part of the storage path is having trouble.
A compatible replacement controller is a practical test if you have one available. Just check the card form factor before ordering or swapping it, since a full-size card and a mini controller may not be interchangeable in the same slot.
Keep track of the existing array configuration and make sure any needed data is backed up before changing storage hardware. Don't initialize or recreate the array just to test the replacement.
Answers are reviewed before publication.
u316+paperclip_8:
I haven't opened it up yet. I'll inspect and reseat the connections and see what compatible spares I have.