RAID1 is DEGRADED, but which disk is faulty?

jesse reynolds jesse at
Wed Sep 3 06:23:54 PDT 2003

Hmmm, doesn't look good:

# atacontrol rebuild ar0
atacontrol: ioctl(ATARAIDREBUILD): Operation not supported by device

any other ideas?

Note that I used the Promise chip's firmware to initially build the 
mirror, so I trust that this is a "RAID capable ATA controller" (from 
the rebuild section of the atacontrol man page)



At 8:12 -0500 3/9/2003, Peter Elsner wrote:
>Try rebuilding the array...
>atacontrol rebuild ar0
>See if that helps...
>Peter Elsner
>At 10:45 PM 9/3/2003 +1000, you wrote:
>>How do you tell which disk has problems in a hardware RAID1 array? 
>>My machine has been up for nearly six months, and only the last 
>>three weeks of messages logs are retained. There is nothing any in 
>>the last three weeks of system logs about any kind of hardware 
>>error, or warning, or anything mentioning ar0, ad4, or ad6.
>>atacontrol is showing a DEGRADED status of the mirror:
>># atacontrol status ar0
>>ar0: ATA RAID1 subdisks: ad4 ad6 status: DEGRADED
>>How does one tell which disk is faulty? Or is it possible that 
>>they've become out of sync and need rebuilding, in which case which 
>>one do I detach and reattach?
>>I'm scared to reboot as it's a running server. What can I do????
>>FreeBSD 4.6.2-RELEASE
>>atapci1: <Promise ATA100 controller> port 
>>mem 0xdffe0000-0xdfffffff irq 11 at device 16.0 on pci0
>>ar0: 76293MB <ATA RAID1 array> [9726/255/63] status: READY subdisks:
>>  0 READY ad4: 76319MB <ST380021A> [155061/16/63] at ata2-master UDMA100
>>  1 READY ad6: 76319MB <ST380021A> [155061/16/63] at ata3-master UDMA100
>># atacontrol list
>>ATA channel 0:
>>     Master:      no device present
>>     Slave:       no device present
>>ATA channel 1:
>>     Master: acd0 <LG DVD-ROM DRD-8160B/1.01> ATA/ATAPI rev 0
>>     Slave:       no device present
>>ATA channel 2:
>>     Master:  ad4 <ST380021A/3.19> ATA/ATAPI rev 5
>>     Slave:       no device present
>>ATA channel 3:
>>     Master:  ad6 <ST380021A/3.19> ATA/ATAPI rev 5
>>     Slave:       no device present
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>Peter Elsner <peter at>
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