On Tue, Jan 19, 2010 at 07:00:03PM +0100, Aleksander Adamowski wrote:
> Concerning the recent rollout of HDDs with 4 kb physical sectors and
install kernel >= 2.6.31, util-linux-ng 2.17, and use fdisk.
You will see :-) The latest fdisk uses disk topology information from
kernel and all partitions should be correctly aligned (you have read
and follow fdisk suggestions -- so read all warnings).
> "So now I get to the silly (question?):
> CentOS tools, like 'fdisk', 'LVM', and 'mkfs.ext3', do have options to
> "align right", if you know what you are doing. No need to wait for
> critical feature updates from upstream. But it seems that they do not
> offer the "4k alignment" (or whatever a particular brand of SSD
> prefers) by default, and that the user has to know the correct magical
the latest fdisk supports alignment to arbitrary phy.block size
(including 64kB blocks for RAIDs), the other feature is that it
supports alignment_offset -- it means 4kB-sector desktop disks with
compensation for DOS compatible partitioning.
> incantations. INET is full of "incantations", but whom can you trust?
> WD attempts to "educate" their customers, should we increase our
> awareness too?"
btw, libparted has been also updated to use the topology data.
> Another question, would using GUID Partition Table (GPT) format be a
> proper solution (as the table has a fixed size of 4 * 4096 bytes)?
Nothing in GPT is fixed, it's also based on sector size. The area for
partitions is defined by {first,last}_usable_lba. I think this area
should be aligned to phy.block boundary.
Note you also need the latest kernel (.32 or .33) because in old
kernels is a bug and it supports 512-byte sectors only.
> If so, is it still true that fdisk does not support GPT (seems that
> it's in the TODO:
> http://git.kernel.org/?p=utils/util-linux-ng/util-linux-ng.git;a=blob;f=TODO;h=9df5b7b447cd4f379caae8d08b59ee18fa641544;hb=HEAD)?
>
> What are the chances that it will be implemented in the near future?
:-)
Now I have some experience with GPT (from kernel, parted and blkid),
so implement this feature should not be a big problem for me (and GPT
has pretty readable standard). The problem is time. I still see more
important things that GPT in fdisk.
Use parted for now. The latest parted supports all necessary features
(I hope;-).
Karel
--
Karel Zak <kzak@xxxxxxxxxx>
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