atacontrol and creating raid-1 arrays

Eirik Oeverby ltning at
Tue Sep 14 02:34:08 PDT 2004

Søren Schmidt wrote:
> Eirik Øverby wrote:
>> Hi,
>> I have just done a 'cp /dev/ad4 /dev/ad6'. Those drives should be 100% 
>> identical (even the same drive models). Will the command
>> 'atacontrol create RAID1 ad4 ad6' ruin the data on my drives?
>> I ask because I am hoping to avoid the need for another 150 gigs of 
>> space just to copy the data off of the drives before creating the 
>> array...
> "depends"
> Since the RAID metadata has to be put on disk it wont work if you have 
> that area used for real data. Depending on what controller you use the 
> metadata can be stored in different places. Other than that it works if 
> you are *sure* the disks are identical (dd with a decnet blocksize is 
> *much* faster tha cp).

Yea, I used dd (blocksize 256kbyte proved optimal; ~40mbyte/sec) for my 
final operation; was testing with cp first to make sure. This is a 
Silicon Image SATA RAID controller which isn't supported by the ATA 
driver in RAID mode, so it's purely software. Which, according to 
another reply I got, uses the last 255 sectors on the disk. These were 
already free, so I just tested - seems to work fine. Fsck has no 
complaints. Other things I should do to verify?


> -Søren

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