[mythtv-users] RAID: full disk or partition (was: Question re: available SATA ports and linux software RAID)

Kevin Ross kevin at familyross.net
Tue Apr 26 07:26:55 UTC 2011

On 4/25/2011 7:23 PM, Jean-Yves Avenard wrote:
> On 26 April 2011 09:04, Kevin Ross<kevin at familyross.net>  wrote:
>> same as the end of the device, then when the computer boots up, when it
>> tries to autodetect raid partitions, it will see a superblock on
>> /dev/sdX, and will stop looking for /dev/sdX1, but the one for /dev/sdX
>> will be invalid.  This caused me lots of grief until I figured out what
>> was going on.  After that, I just shrunk the partition by 8 blocks, and
>> everything was happy.
> I guess it all depends what type of partition you set. The mdadm FAQ
> clearly states not to use the auto-detect RAID type. So this shouldn't
> be a problem.
> I have used full disk size partitions forever and never saw a problem.

In the past, when I created partitions with fdisk, I thought I was 
creating partitions that were filling the entire disk.  Only after using 
the -u option (specify sectors instead of tracks) did I find out it was 
actually leaving a little extra space at the end of the disk.  However, 
when I created partitions using the -u option, which I was doing because 
I got some new 4KB-sector size drives, it let me create partitions 
really to the end of the disk, which is when I ran into problems.

Check some of your existing partitions using "fdisk -lu" and see if the 
partitions really go to the very end of the drive, or if there is a 
little extra space there.

Also, I didn't know you weren't supposed to use the RAID autodetect 
partition type.  Thanks for the heads up.

-- Kevin

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