ATA Raid

[Bill Gradwohl]

Has anyone tested an ATA Raid 1 setup that utilizes the hptraid.o,
pdcraid.o, or silraid.o modules?

By testing I mean force a failure and see what happens. 

I spun up a copy of Fedora on a TYAN dual P3 mobo that has a Promise 20267
chip, applied all the recommended patches via up2date, and insmod'd ataraid
and pdcraid, formatted and then mounted a partition for testing. 

I was surprised to find that the Promise controller allowed the O/S to find
hde and hdf even though I used both identical drives to create a single
RAID1 array via the Promise BIOS. My Google research suggests that all these
mobo installed RAID controllers don't provide real hardware RAID, but offer
a quasi (and I think unreliable) hardware/software solution. Is that true?

I wrote all over the array and that went well. I even used up 100% of the
array space and there was no unexpected behavior. However, when I forced a
failure by removing power from one of the drives, the BASH script I was
using to write files all over the array failed after a few seconds. I was
expecting the remaining good drive to pick up the slack, but the partition
turned into a read only partition. I unmounted and remounted and it was
still read only. What good is that?

I powered the machine down reattached the power cable to the one drive I had
removed it from, and the PROMISE boot BIOS showed that the array was
healthy. ????? After the O/S loaded I mounted the partition again, and it
was read/write. However, the data was trashed. 

Has anyone performed similar testing successfully on any of the kernel
supported raid modules I listed previously, or are folks just trusting these
arrays to do the right thing when the time comes?

Bill Gradwohl
YCC
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