Raw disk with large file support

[Scott G. Gallup]

I am totally confused re: raw disk set up with large file support enabled.
I have a 9.1 Gb disk (/dev/dsk/c0t5d0) in a K460 HP-UX 11.0 (64bit) with INFORMIX ids 9.40. I want the entire disk to be a raw device with large file support enabled.
Do I need to create a logical volume and then not mount it?
Would the correct steps be:
# pvcreate -f /dev/rdsk/c0t5d0
# mkdir /dev/vg03
# cd /dev/vg03
# mknod group c 64 0X01000
# vgcreate vg03 /dev/dsk/c0t5d0
# lvcreate -L 8672 /dev/vg03
# mkfs -F vxfs -o largefiles /dev/vg03/rlvol1
# newfs -F vxfs -o largefiles /dev/vg03/rlovl1

Would I need to add anything to /etc/fstab to ensure that large file support is enabled following reboots?

Any advice, comments, clarification would be greatly appreciated.

Thank you,

Scott

[Paul Sperry · Accepted solution]

mkdir /dev/vg03
mknod /dev/vg03/group c 64 0x010000
pvcreate /dev/rdsk/c0t5d0 vgcreate /dev/vg03 /dev/rdsk/c0t5d0
lvcreate -L 8672 -i 3 -I 64 -n rvol1 /dev/vg03
newfs -F vxfs -o largefiles /dev/vg03/rvol1

/etc/fstab

/dev/vg03/rvol1 /rvol1 vxfs rw,suid,largefiles,delaylog,datainlog 0 2

[Martin Johnson]

For a raw disk, you would not create a file system in the logical volume. You would make the logical volume available to INFORMIX and let it determine how the space is used.

You *can* create a file system on the logical volume, but then it is no longer considered raw (some call it "cooked").

HTH
Marty

[Paul Sperry]

The pvcreate and vgcreate are separate commands I have noticed that some times when you reply to a question it dosn't post the way you tiped it :(

[A. Clay Stephenson]

Hi Scott:

You managed to totally confuse me as well. Is it largefiles or raw disks? The two have absolutely nothing to do with each other. If you are using raw disks then a filesystem doesn't even come into the picture and thus the largefile mount option is meaningless.

[Sridhar Bhaskarla]

Hi Scott,

If you are going to use it as a raw disk (using the device file /dev/vg03/rlvol1), then you do not need to bother about large files.

If your plan is to use the filesystem (using the device file /dev/vg03/lvol1 by mounting it on some directory), then your method is correct. You do not need to add anything to the fstab. If largefiles is enabled, it will be mounted with it by default. TO verify it do the following.

#mkdir /test
#mount /dev/vg03/lvol1 /test
#mkfs -m /dev/vg03/lvol1

It should printout whether the filesystem is with largefiles or not.

-Sri

[Leif Halvarsson_2]

Hi,
This must be a misunderstanding. If an application (e.g. uses a raw device the OS dont bother about the structure on this device. From HP-UX point ov view it is only a large bunch of bytes. It is up to the application how it is used.

[Scott G. Gallup]

Thanks to everyone who has responded. Apparently my confusion, and thus everyone else's, is due ignorance on my part (first time that I've ever used raw disk devices).

If I understand Sri & Clay correctly I am making a mountain out of a molehill. A dba-type helping me convert an Informix database wants to use raw disk but then said that large file support needed to be enabled on the device because the combined size of all the tables will be greater than 2Gb.

Thanks

[A. Clay Stephenson]

You simply need to stop at the lvcreate step. Your other option is to use real raw disk and just use the /dev/rdsk/c0t5d0 but, in general, the LVM overhead is so slight and the flexibility it offers (like striping across multiple raw disks or mirroring) that the almost unmeasurable overhead is well worth it.

[Dave Wherry]

Here is another thread you may want to review.
http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0xf75228c64656d71190080090279cd0f9,00.html

Since you mentioned that a dba-type started you on this path he/she may want to read it also.