Re: Why LVM metadata locations are not properly aligned

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On 21.4.2016 11:54, Zdenek Kabelac wrote:
On 21.4.2016 06:08, Ming-Hung Tsai wrote:
Hi,



1. The metadata locations (raw_locn::offset) are not properly aligned.
    Function _aligned_io() requires the IO to be logical-block aligned,
    but metadata locations returned by next_rlocn_offset() are 512-byte
aligned.
    If a device's logical block size is greater than 512b, then LVM need to use
    bounce buffer to do the IO.
    How about setting raw_locn::offset to logical-block boundary?
    (or max(logical_block_size, physical_block_size) for 512-byte logical-/4KB
     physical-block drives?)

This looks like a bug - lvm2 should start to write metadata always on physical
block aligned position.

Hi

I've opened RFE BZ for this one - https://bugzilla.redhat.com/1329234
It's not completely trivial to fix this in a backward compatible way - but I'm mostly 100% sure it's not cause your 10s delay unless.

Regards

Zdenek

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