HP Microserver N40L RAID errors

 

The HP MicroServers (N36L/N40L/N56L) were bargains when they first released costing around £100 after cashback. Although their CPUs are pretty slow by modern standards they still make good NAS servers as they take standard 3.5" SATA drives.

I've got one running Windows 10 Pro from an SSD in the CD-ROM bay, leaving all the bays free for data drives running in AHCI (non RAID) mode. I recently upgraded from 2TB to 4TB data drives to give myself a bit more backup space. 

The lazy way to upgrade is to pull a drive, replace it and then let the array rebuild. Repeat this process for each drive and at the end you can expand the volumes. During this process though the data is at risk because should a remaining drive fail, everything is lost. The drive bays on these servers aren't hotswap so they do need to be powered off first.

The correct expansion method is to add a new disk to the storage pool, prepare the old drive for removal and then finally remove it. A USB caddy is a good way to temporarily add an extra drive. My advice is to add some USB3 ports via a PCIe card else you'll be waiting for days at USB2 speeds.

At first I tried the lazy method as this server only contains backup data but had problems rebuilding. I had 4 new drives and each one failed with multiple I/O errors, dropping offline and machine lockups. Checking the drives on another PC found no errors on the drives and they worked fine.

After a lot of experimentation I found it to be a problem with the default Microsoft AHCI driver and the AMD chipset in this server. Despite AMD saying to use the default driver with Windows 10, it actually works reliably with their amd_sata.sys version 1.2.1.402 driver.