On Thu, 12 Feb 2004 22:28:11, Nathan Scott wrote:
> On Thu, Feb 12, 2004 at 09:33:07PM +0100, Miquel van Smoorenburg wrote:
> > ...
> > However there's still one issue:
> >
> > I created a LVM volume on /dev/sda2, called /dev/vg0/test. Then
> > I created and mounted an XFS partition on /dev/vg0/test. XFS uses
> > a 512 byte blocksize by default, but the underlying /dev/sda2
>
> (thats a 512 byte "sector size" in XFS-speak)
Ah yes. mkfs -txfs -s size=4096 fixes it as well, but that's a
workaround.
> > device had a soft blocksize of 4096 (default after boot is 1024,
> > but I had been mucking around with it so it got set to 4096).
> >
> > As a result, I couldn't get more than 35 MB/sec write speed out
> > of XFS mounted on the LVM device.
> >
> > I added this little patch:
> >
> > --- drivers/md/dm-table.c.ORIG 2004-02-12 20:49:47.000000000 +0100
> > +++ drivers/md/dm-table.c 2004-02-12 20:56:59.000000000 +0100
> > @@ -361,7 +361,7 @@
> > blkdev_put(bdev, BDEV_RAW);
> > else {
> > d->bdev = bdev;
> > - set_blocksize(bdev, d->bdev->bd_block_size);
> > + set_blocksize(bdev, 512);
> > }
> > return r;
> > }
> >
> > This forces the underlying device(s) to a soft blocksize of 512. And
> > I had my 80 MB/sec write speed back !
Gah, wrong patch. That's because vim saved dm-table.c when I suspended it
to copy dm-table.c to dm-table.c.ORIG, so the patch makes no sense.
--- drivers/md/dm-table.c.ORIG 2004-02-12 23:05:15.000000000 +0100
+++ drivers/md/dm-table.c 2004-02-12 20:56:59.000000000 +0100
@@ -359,8 +359,10 @@
r = bd_claim(bdev, _claim_ptr);
if (r)
blkdev_put(bdev, BDEV_RAW);
- else
+ else {
d->bdev = bdev;
+ set_blocksize(bdev, 512);
+ }
return r;
}
That's more like it.
> > I'm not sure if setting the blocksize of the underlying device
> > always to 512 is the right solution. I think that set_blocksize
>
> I would guess that bdev_hardsect_size()
> would be more appropriate here than hard-coding 512 bytes. I
> don't know the details of the problem being solving by adding
> set_blocksize() in there though, so I might be completely wrong.
That does make sense, I guess.
Mike.
_______________________________________________
linux-lvm mailing list
linux-lvm@redhat.com
https://www.redhat.com/mailman/listinfo/linux-lvm
read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
