Hammer and mirrored disks

A frequent question people ask when trying Hammer is “How can I do software RAID to cover a disk failure?”  Hammer provides for streaming one volume to another, so you can duplicate drives, but there isn’t an automatic failover mechanism as there is with a RAID setup.  The first answer is usually “get hardware RAID“; my preferred solution.   The remaining software solutions are vinum, ccd, and lvm for DragonFly.

Heads up: changing mfi to mrsas

The mfi(4) driver has had some data corruption problems on “Thunderbird” series RAID controllers.  There’s a newer driver, mrsas(4), that replaces mfi(4) for these controllers and does not have these issues, but switching may mean new drive locations and therefore some work to get booting correctly again.  Sascha Wildner has an extensive writeup about what this entails, and how to switch now if you have that hardware (recommended).

Try installing DragonFly again

Did you try to install DragonFly relatively recently and it never made it past the bootloader?  Apparently there’s a bug in some BIOS when using a smaller USB drive to install.  The loader checks multiple places for information, and if it checks somewhere that’s ‘farther’ than the end of the disk (i.e. 6G on a 4G USB key), the machine locks up.

Matthew Dillon and Kyle Davis spent a good number of hours figuring this out today, and Matt committed a fix.   So, if you were bit by this problem, try a -LATEST image about 24 hours from now and see if it works.