On 2/6/11 3:30 PM, John R Pierce wrote:
>
>> Does anyone know if 4k sectors will be handled better by the kernel in Centos6?
>> I'd like to copy backups to a 750Gb laptop type drive for offsite storage but
>> the best write speed I can get is about 8MB/sec even with dd to the raw disk
>> which shouldn't have an issue with partition alignment.
>
>
> what are you using on dd as the blocksize (bs=) ? should be a fairly
> large multiple of 4K, like 1048576 (eg, 1MB writes).
>
> I get 50-80MB/sec writes to a laptop drive hooked up to my windows
> desktop when I'm cloning said laptop drives. if you're only seeing
> 8MB, something is very wrong.
Not all laptop drives use 4k sectors - probably just 750Gb and up.
I was using obs=4M. I thought there was more to it than alignment - and changes
were made in more current kernels to help with the speed.
--
Les Mikesell
lesmikesell at gmail.com