[lkml]   [2001]   [Nov]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Subjectconfused about raw-io blocksizes

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.

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.

When doing dd on the block special files bs=512 is always OK.

The reason I messing with this is that I'm working with an animal called
Oracle Real Application Cluster 9i which need a partiontion on a shared
disk to hold the cluster config. Installation stopped because the program
oracle provides to format the partition do 512 byte io, and require a
character raw device...



Terje Eggestad
Scali Scalable Linux Systems

Olaf Helsets Vei 6 tel: +47 22 62 89 61 (OFFICE)
P.O.Box 70 Bogerud +47 975 31 574 (MOBILE)
N-0621 Oslo fax: +47 22 62 89 51

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-03-22 13:13    [W:0.370 / U:0.020 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site