Re: [gentoo-user] Re: Gentoo on a Dell XPS 13 Ultrabook

[Joshua Murphy]

On Mon, Mar 5, 2012 at 11:00 AM, Alex Schuster <wonko@×××××××××.org> wrote:
> Grant writes:
>
>> > The performance is only impacted if the sector size is something other
>> >  than 512 bytes. The newer 4K sector size used by some higher density
>> > drives requires that you start partitions on a sector boundary or they
>> > will perform badly. There isn't an actually performance need to
>> > actually start on 2048 but the fdisk-type developer folks are doing
>> > that to be more compatible with newer Windows installations.
>>
>> All my drives says this from fdisk:
>>
>> Units = sectors of 1 * 512 = 512 bytes
>> Sector size (logical/physical): 512 bytes / 512 bytes
>> I/O size (minimum/optimal): 512 bytes / 512 bytes
>
> Neither fdisk nor hdparm seem to get the correct sector size, at least
> not always. That's what I read somewhere (and not only once), and it's
> true for my own 2TB drive which I know to have a 4K sector size. I'd say
> you have to look up the specs on the vendor's web size to be sure.
>
>> So it doesn't matter where the first partition starts?
>
> If you have 4K sectors (and not a Seagate drive with SmartAlign [*]), it
> does.
>
> BTW, here's some benchmarks I just stumbled upon:
> http://hothardware.com/Articles/WDs-1TB-Caviar-Green-w-Advanced-Format-Windows-XP-Users-Pay-Attention/?page=2
>
> [*] I don't want to sound like I'm advertising for Seagate here, but at
> least it seems that with SmartAlign the performance impact will be
> much less, so it might not be worth the trouble of re-partitioning drives
> that are already being used.
>
>        Wonko

Also, it counts with SSDs, where alignment,or lack therof, with the
erase block becomes noticeable on write performance. Finding the
actual size of an erase block for most SSDs is rather difficult, but
1MB tends to be a reliable guess as a multiple of *that* as well.

-- 
Poison [BLX]
Joshua M. Murphy