Messages in this thread | | | Date | Fri, 9 Nov 2001 17:13:11 -0700 | From | Andreas Dilger <> | Subject | Re: confused about raw-io blocksizes |
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On Nov 10, 2001 00:52 +0100, Terje Eggestad wrote: > I'm curious as to what sets the smallest legal blocksize for raw-io, I > get different values for different partitions on the same disk drive. > > In all my tests I've used > raw /dev/raw/raw2 <block speclial file> > and to test block size: > dd if=/dev/raw/raw2 of=/dev/null bs=N count=1 > where N is either 512, 1024, or 4096. > (I've a RH7.1 with a dd that do propper buffer alignment) > Failure is always "invalid argument" which singify either misaligned > buffer or illegal read length. > > What confuses me is that when raw2 is bound to /dev/hda bs=512 is ok. > However when binding raw2 to the different partitions on /dev/hda, some > are ok with 512, some will only accept 1024, and one required 4096.
It may be getting confused with the filesystem blocksize. Check tune2fs -l for those devices.
> When creating an lvm vg on one partition (/dev/hda6), and I've created > two logical volumes on it, one was ok with 1024 and the other required > 4096. When binding a raw to /dev/hda6 dd with bs=512 was ok.
LVM is broken in this regard, unless you have a recent patch (Linus' kernel does not). I sent him a patch to fix that, but it did not get in.
What kernel version/LVM do you have? Are you using LVM on all of these partitions, or only some? Did you have filesystems on them?
Cheers, Andreas -- Andreas Dilger http://sourceforge.net/projects/ext2resize/ http://www-mddsp.enel.ucalgary.ca/People/adilger/
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