On Thu, Dec 17, 2009 at 1:28 PM, Kenneth Westerback
<kwesterback@gmail.com> wrote:
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> On Wed, Dec 16, 2009 at 9:21 PM, Aaron Mason <simplersolution@gmail.com>
wrote:
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>> On Thu, Dec 17, 2009 at 12:46 PM, Kenneth Westerback
>> <kwesterback@gmail.com> wrote:
>>> On Wed, Dec 16, 2009 at 7:12 PM, Marco Peereboom <slash@peereboom.us>
wrote:
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>>>> yes
>>>>
>>>> On Thu, Dec 17, 2009 at 12:30:46AM +0100, Robert wrote:
>>>>> Hi,
>>>>>
>>>>> I just read [1,2] that Western Digital (and probably others) will start
>>>>> to sell disks with an internal block size of 4KB instead of 512 byte.
>>>>>
>>>>> The article mentions that this might lead to a considerable performance
>>>>> impact if the  logical partition alignment is not in sync with the
>>>>> physical one ("e.g. if partitions starts at sector 63 wich is not a
>>>>> multiple of 4KB" [1]):
>>>>> "If a block of 4KB should be written, which is (logically) aligned, but
>>>>> physically in fact 2 sectors, then both physical sectors will need to
be
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>>>>> read, partially modified and then written back which leads to a serious
>>>>> performance hit." [1]
>>>>>
>>>>> Any comments from someone who has a good knowledge of this area? Will
>>>>> this affect OpenBSD?
>>>>>
>>>>> regards,
>>>>> Robert
>>>>>
>>>>> [1] (german)
>>>>>
>>>
http://www.heise.de/newsticker/meldung/Festplatten-mit-4-KByte-Sektorgroesse-
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>>> 887759.html
>>>>> [2]
http://www.wdc.com/wdproducts/library/whitepapers/en/2579-771430.pdf
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>>>>
>>>>
>>>
>>> 4K sectors themselves should work ok as we already do that for ffs on
>>> CD media. Which works the last I checked. Ensuring alignment on blocks
>>> will have to be checked. It sounds like some should donate a few of
>>> these 4K devices to the project so we can fix any issues asap.
>>>
>>> .... Ken
>>>
>>>
>>
>> I'm looking into the possibility of modifying QEMU for testing this.
>> Not sure how close such things would be to reality, but it's worth a
>> look in any case and would drop the cost of development significantly.
>>
>> --
>> Aaron Mason - Programmer, open source addict
>> I've taken my software vows - for beta or for worse
>>
>
> If you just want to see what you can do with/to 4K sectors, read the
> vnconfig man page (-t option) and create yourself some 4K sector
> devices in your disktab.
>
> However without hardware testing you never know what the clever dicks
> at the vendor have done. :-).
>
> .... Ken
>

That's a good point.

From what I've seen, 4k blocks are supported by most filesystems
anyway - and besides, provided the partitions are created on 4k block
boundaries, there's no reason for any concern IMHO.

I could be wrong - I'm a programmer, not an engineer.

--
Aaron Mason - Programmer, open source addict
I've taken my software vows - for beta or for worse