Re: Is squeeze compatible woth WD20EARS and other 2TB drives?
On Mon, Dec 13, 2010 at 05:40:42PM -0600, Stan Hoeppner wrote:
> Jochen Schulz put forth on 12/13/2010 3:51 PM:
> > Mike Viau:
> >>> On Mon, 13 Dec 2010 21:46:59 +0100 <ml@well-adjusted.de> wrote:
> >>>
> >>> Partition 1 does not start on physical sector boundary.
> >>
> >> I don't understand the implied meaning of this error? Did you take any
> >> precautions as to the alignment of your partition? What about if you
> >> were planning on having multiple partitions?
>
> >From the linux-ide mailing list April 2010:
>
> http://www.spinics.net/lists/linux-ide/msg37306.html
>
> Unfortunately, sfdisk and cfdisk have no clue about alignment and
> disks topology.
>
> Now only the fdisk and parted commands are ready for new disks.
>
>
> So the proper title of this thread should be:
>
> "Does the Squeeze installer use fdisk or parted?"
>
> As of April 2010, only fdisk and parted will create sector boundary
> aligned partitions on drives that internally translate from 4K to 512B
> sectors.
>
> Linux typically reads 4K blocks. With a translated drive, two or more
> 512 byte sectors of a given block may lie on opposite sides of a
> hardware 4K sector boundary. Thus, Linux will have to read two
> consecutive hardware sectors instead of one in order to get the contents
> of the 4K logical block. I.e. two reads (head seeks) per every 4k block
> instead of one. Thus, you get half the performance vs a properly
> aligned cylinder.
>
> In the case of the WD20EARS this will drop your peak sequential read
> rate from over 100 MB/s down to 50 MB/s or less. Without proper
> alignment, you're literally leaving half of your drive's sequential read
> performance on the table.
>
> The story is even worse for 4K random writes. You'll drop your write
> performance by a factor of 4 or more if you don't have proper alignment:
>
> The moral of the story is, use fdisk or parted and make sure your
> partitions are correctly aligned on 4KB boundaries. If the Squeeze
> installer doesn't do so, I'd recommend booting an ISO or USB live distro
> and partition the drive with fdisk or parted before booting the Squeeze
> installer.
Hi Stan,
That is fascinating to learn, especially the fdisk
is among the best tools for disk partitioning.
I was going to ask about my disk, but I see that my message
is
Partition 1 does not end on cylinder boundary.
Which seems to be different than the OP's physical sector size
message.
If partition 1 is off, does that mean *all* partitions are
off? How does one verify? (I used MiniTool Partition Wizard
to shrink my laptop's Windows 7 partition, handling all the
magical, Linux-hating files -- MFT, etc.)
http://www.partitionwizard.com/free-partition-manager.html
FWIW, my disk partitioning follows.
Thanks for posting this information!
Joel
Disk /dev/sda: 320.1 GB, 320072933376 bytes
255 heads, 63 sectors/track, 38913 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x27b11b56
Device Boot Start End Blocks Id System
/dev/sda1 * 1 154 1228800 7 HPFS/NTFS
Partition 1 does not end on cylinder boundary.
/dev/sda2 154 4742 36860288+ 7 HPFS/NTFS
/dev/sda3 4743 5251 4088500 82 Linux swap / Solaris
/dev/sda4 5252 38914 270398047+ f W95 Ext'd (LBA)
/dev/sda5 5252 7163 15358108 83 Linux
/dev/sda6 7164 37638 244790404 83 Linux
/dev/sda7 37639 38914 10240000 7 HPFS/NTFS
> --
> Stan
>
>
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--
Joel Roth
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