Reason for md raid1 max_sectors_kb limited to 127?

[Sebastian Riemer <sebastian.riemer@xxxxxxxxxxxxxxxx>]

Hi list,

I'm wondering why max_sectors_kb is set to 127 with md raid1.
This value is at 512 on normal HDDs.

If I do a file copy on ext4 on a normal HDD then I can see with
blktrace/blkparse that 128 KiB chunks are read and 512 KiB chunks are
written.

With md raid it looks like this: 124 KiB, 4 KiB, 124 KiB, 4 KiB, ... .
This looks very inefficient.

So, is there a particular reason that max_sectors_kb is set to 127?

Cheers,
Sebastian

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Sebastian Riemer
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