I recently became one of the growing number of users seeing WRITE_DMA-related panics on a regular basis any time I loaded down my system. I'd tried the workaround of running my main 120GB drive in PIO4 mode, but it was unbearably slow and the system crawled during large transfers.
I'd been installing FreeBSD on vinum concat volumes for several years for the flexibility in allocating storage (want to grow /usr? Just tack another plex to the end and growfs it). However, I'd noticed that my storage requirements had pretty well stabilized over the last couple of years, and I decided to remove my vinum setup in favor of traditional partitions. When I did that, my WRITE_DMA problems disappeared completely under all circumstances that I've been able to test. I have been totally unable to panic my system (or get any kind of DMA warnings) since the migration. I'm not ready to completely blame vinum for destabilizing my ATA system - I wouldn't testify in court that I didn't inadvertently change any seemingly minor but actually important setting - but the circumstantial evidence seems pretty strong for me. -- Kirk Strauser
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