Les Mikesell wrote:
> Robert Nichols wrote:
>> On 05/22/2010 11:29 AM, Les Mikesell wrote:
>>> Robert Nichols wrote:
>>>> On 05/21/2010 07:39 PM, Robert Nichols wrote:
>>>>> You have another way out. By my calculation, that drive is partitioned
>>>>> in DOS compatibility mode, which leaves the remainder of the MBR track
>>>>> unused. Running fdisk in expert mode ("x" command), you can move the
>>>>> partition's beginning of data ("b" command) from sector 63 back to
>>>>> sector 56. That will give you the needed 4K alignment and a partition
>>>>> that is no smaller than what it was before.
>>>> Right idea, not the right procedure. You'll need to turn off DOS
>>>> compatibility mode, then create the partition, and then go into
>>>> expert mode and move the beginning of data from sector 1 to sector
>>>> 56.
>>>>
>>> It ended up like this, but still sync'ing at about 4M/sec instead of 40.
>>>
>>>
>>> Expert command (m for help): p
>>>
>>> Disk /dev/sdh: 255 heads, 63 sectors, 91201 cylinders
>>>
>>> Nr AF Hd Sec Cyl Hd Sec Cyl Start Size ID
>>> 1 00 0 2 0 254 63 64 56 1465144009 fd
>> Is that one of those WD drives that falsely reports its physical sector
>> size as 512 bytes? I don't know if the kernel can always do the right
>> thing when that happens, but all the reports I've seen say that getting
>> the start of the partition aligned properly is sufficient.
>>
>> What does "hdparm -I /dev/sdh | grep 'Sector size'" show?
>
> It doesn't mention sector size. All of the size related options seem to match
> the Seagate desktop drive.
>
Does the 4K sector size mean that the drive is going to read the 4K chunk then
merge in the 512 bytes you wrote, the wait for the sector come around again to
write it back? I guess that could explain the 10x write speed difference
regardless of cylinder alignment. Read speed doesn't seem that much different.
--
Les Mikesell
lesmikesell at gmail.com