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Subject: Re: Advanced disk format at WD20EARS: what should "camcontrol
 identify" show?
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On 04/04/2011 08:10, Lev Serebryakov wrote:
> Hello, Alexander.
>
>      I'm replacing old WD500AAKS HDDs in my (software) RAID5 with new
> WD20EARS, which are advanced format. And speed is terrible. RAID5
> rebuilding shows about 8MiB/s (55MiB/s is typical speed for old AAKSes)...
>
>    I'm affraid, that my HDD is in some strange mode with 512 byte
> sectors emulation:

With such drives, everything must be 4 KiB-aligned : the RAID stripes, 
the partitions / slices and the file system / block size. This is the 
only way to get good performance.

If you just replace a non-4K drive in a RAID5 with a 4K drive, it is 
very likely that there would be alignment problems with that drive.