Re: [gentoo-user] 1-Terabyte drives - 4K sector sizes? -> bar performance so far

[Mark Knecht <markknecht@gmail.com>]

On Mon, Feb 8, 2010 at 4:05 PM, Frank Steinmetzger <Warp_7@gmx.de> wrote:
> Am Sonntag, 7. Februar 2010 schrieb Mark Knecht:
>
>> Hi Willie,
>>    OK - it turns out if I start fdisk using the -u option it show me
>> sector numbers. Looking at the original partition put on just using
>> default values it had the starting sector was 63
>
> Same here.
>
>> - probably about the worst value it could be.
>
> Hm.... what about those first 62 sectors?
> I bought this 500GB drive for my laptop recently and did a fresh partitioning
> scheme on it, and then rsynced the filesystems of the old, smaller drive onto
> it. The first two partitions are ntfs, but I believe they also use cluster
> sizes of 4k by default. So technically I could repartition everything and
> then restore the contents from my backup drive.
>
> And indeed my system becomes very sluggish when I do some HDD shuffling.
>
>> As a test I blew away that partition and
>> created a new one starting at 64 instead and the untar results are
>> vastly improved - down to roughly 20 seconds from 8-10 minutes. That's
>> roughly twice as fast as the old 120GB SATA2 drive I was using to test
>> the system out while I debugged this issue.
>
> Though the result justifies your decision, I would have though one has to
> start at 65, unless the disk starts counting its sectors at 0.
> --
> Gruß | Greetings | Qapla'
> Programmers don’t die, they GOSUB without RETURN.
>

Good question. I don't know where it starts counting but 63 seems to
be the first one you can use on any blank drive I've looked at so far.

There's a few small downsides I've run into with all of this so far:

1) Since we don't use sector 63 it seems that fdisk will still tell
you that you can use 63 until you use up all your primary partitions.
It used to be easier to put additional partitions on when it gave you
the next sector you could use after the one you just added.. Now I'm
finding that I need to write things down and figure it out more
carefully outside of fdisk.

2) When I do something like +60G fdisk chooses the final sector, but
it seems that it doesn't end 1 sector before something divisible by 8,
so again, once the new partition is in I need to do more calculations
to find where then next one will go. Probably better to decide what
you want for an end and make sure that the next sector is divisible by
8.

3) When I put in an extended partition I put the start of it at
something divisible by 8. When I went to add a logical partition
inside of that I found that there was some strange number of sectors
dedicated to the extended partition itself and I had to waste a few
more sectors getting the logical partitions divisible by 8.

4) Everything I've done so far leave me with messages about partition
1 not ending on a cylinder boundary. Googling on that one says don't
worry about it. I don't know...

So, it works - the new partitions are fast but it's a bit of work
getting them in place.

- Mark