Re: LVM write performance

[Ivan Shmakov <ivan@gray.siamics.net>]

>>>>> Stan Hoeppner <stan@hardwarefreak.com> writes:

[…]

 > The horrible performance with bs=512 is likely due to the LVM block
 > size being 4096, and forcing block writes that are 1/8th normal size,
 > causing lots of merging.  If you divide 120MB/s by 8 you get 15MB/s,
 > which IIRC from your original post, is approximately the write
 > performance you were seeing, which was 19MB/s.

	I'm not an expert in that matter either, but I don't seem to
	recall that LVM uses any “blocks”, other than, of course, the
	LVM “extents.”

	What's more important in my opinion is that 4096 is exactly the
	platform's page size.

--cut: vgcreate(8) --
       -s, --physicalextentsize PhysicalExtentSize[kKmMgGtT]
              Sets the physical extent size on physical volumes of this volume
              group.  A size suffix (k for kilobytes up to t for terabytes) is
              optional, megabytes is the default if no suffix is present.  The
              default is 4 MB and it must be at least 1 KB and a power of 2.
--cut: vgcreate(8) --

[…]

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