Help with lvdisplay output

[Nikhil_1]

Hi,

I need some help with understanding the lvdisplay output.

1. What is the 'schedule' field in lvdisplay output?
The man page says "Schedule Striped, sequential or parallel scheduling policy. Striped policy is by default parallel scheduling for mirrored I/O". Could someone please elaborate? What exactly is this scheduling? Who uses it? the controllers? Who creates these schedules?

2. If I have "Logical Extent Based striping" for a volume (the concept is very similar to RAID 1 + 0), then what does the lvdisplay output look like (will it have non-zero values for the "Mirror copies" and "Stripes" fields in lvdisplay? How do I find out whether the given volume uses "Logical Extent Based striping"?

3. Does HP-UX LVM support RAID5? If yes, how do I detect it using the LVM commands?

If it possible for someone to send me the output of lvdisplay for RAID0, RAID1, RAID 1 + 0 (mirroring with LE based striping), that would be tremendous!

With best regards,
Nikhil

[Stefan Farrelly · Accepted solution]

1. Theres really only 2 schedules; parallel for mirrored or extend-based mirrors (1st and 3rd examples in 3. below) or if you use the -i -I options for striping then its a striped schedule. Schedule basically means lvm formatting policy (normal = parallel or striped for striped which means the lvm format is completely different).

2. Mirror copies will still display 0 (no mirrors). You can see the differences in the example output below.

3. No. But with HP-UX 11i you can install Veritas Volume manager (and use it instead of LVM) and it does support Raid5 using software.

Output from a MIRRORED logical volume
--- Logical volumes ---
LV Name /dev/vg00/lvol4
VG Name /dev/vg00
LV Permission read/write
LV Status available/syncd
Mirror copies 1
Consistency Recovery MWC
Schedule parallel
LV Size (Mbytes) 120
Current LE 30
Allocated PE 60
Stripes 0
Stripe Size (Kbytes) 0
Bad block on
Allocation strict
IO Timeout (Seconds) default

Output from a STRIPED logical volume (over 2 disks);
--- Logical volumes ---
LV Name /dev/vg02/lvol1
VG Name /dev/vg02
LV Permission read/write
LV Status available/syncd
Mirror copies 0
Consistency Recovery MWC
Schedule striped
LV Size (Mbytes) 104
Current LE 26
Allocated PE 26
Stripes 2
Stripe Size (Kbytes) 64
Bad block on
Allocation strict
IO Timeout (Seconds) default

Output from a STRIPED and MIRRORED lvol (striped over 2 disks mirrored to 2 other disks but as its extent based striping the Stripes value below is 0 - its using the PE size of 4Mb for each stripe);
--- Logical volumes ---
LV Name /dev/vg02/lvol1
VG Name /dev/vg02
LV Permission read/write
LV Status available/syncd
Mirror copies 1
Consistency Recovery MWC
Schedule parallel
LV Size (Mbytes) 400
Current LE 100
Allocated PE 200
Stripes 0
Stripe Size (Kbytes) 0
Bad block on
Allocation PVG-strict/distributed
IO Timeout (Seconds) default

--- Distribution of logical volume ---
PV Name LE on PV PE on PV
/dev/dsk/c1t4d0 50 50
/dev/dsk/c1t0d0 50 50
/dev/dsk/c1t3d0 50 50
/dev/dsk/c1t8d0 50 50

[Nikhil_1]

Thanks a lot stefan! This is the information I needed.

So the difference between the output of lvdisplay for a
- mirrored volume and
- a mirrored volume with LE based striping
is in the Allocation field value:

For mirrored: it's strict,
But for mirrored with LE based striping: it's PVG-strict/distributed
(stress on distributed? meaning the extents are not from the same PV and distributed across multiple PVs?)

I have another question.
4. If the disk is not under LVM control, pvdisplay won't show any information about that disk. So if there are plain partitions on the disk, is there a simple tool that will show me the partition layout on that disk (similar to the fdisk/iostat tool on other OSs)?
(or any documentation link to storage mgmt without LVM on HP-UX would be helpful).

With regards,
Nikhil

[Stefan Farrelly]

Hi Nikhil,

"For mirrored: it's strict, But for mirrored with LE based striping: it's PVG-strict/distributed (stress on distributed? meaning the extents are not from the same PV and distributed across multiple PVs?)"

Yes, distributed in essence means 'striped' across all pv's in the PVG's (physical volume groups. When I added the disks into my lvol I added them into groups by using the -g option)

"I have another question.
4. If the disk is not under LVM control, pvdisplay won't show any information about that disk. So if there are plain partitions on the disk, is there a simple tool that will show me the partition layout on that disk (similar to the fdisk/iostat tool on other OSs)? (or any documentation link to storage mgmt without LVM on HP-UX would be helpful)."

Yes, pvdisplay wont display anything if not under LVM control. If not under LVM control then what control ? I dont know of any other programs under HP-UX which could control it apart from LVM or VxVM (Veritas vol mgr). Veritas have their own vx... tools to display VxVM partitions. If you know of another application which can partition disks under HP-UX then you need to consult with the makers of thar app for a tool to display their partitions. Even if you are using RAW partitions these are under LVM control - so at least the VG and PV commands will work, just not LV... commands as their are no Lvols on them.

Cheers,

Stefan

[Nikhil_1]

Please pardon my naive doubts, I am quite new to HP-UX.

By plain partitions, I mean the equivalent of "slices" on Solaris. Is it possible to attach and use a disk from pre-LVM era on HP-UX (which doesn't contain volumes, extents etc. but simple disk partitions). So the disk is not initialized as LVM disk, but directly accessed.

Or when I add such a disk, I have to "upgrade/convert" it to LVM disk first, and then start using it?

With regards,
Nikhil

[Stefan Farrelly]

"By plain partitions, I mean the equivalent of "slices" on Solaris. Is it possible to attach and use a disk from pre-LVM era on HP-UX (which doesn't contain volumes, extents etc. but simple disk partitions). So the disk is not initialized as LVM disk, but directly accessed."

It is possible to use 'slices' on HP-UX but only with older unsupported versions of HP-UX - 9.05 and older (7.x, 8.x). These were pre LVM days. With 10.x and 11.x you use LVM only - you cannot use slices anymore. You could attach an old disk with 'slices' on but I doubt you could access them at all under HP-UX 10.x and 11.x

"Or when I add such a disk, I have to "upgrade/convert" it to LVM disk first, and then start using it?"

Yes, if you have such an old disk with 'slices' on then once you pvcreate -f it then the old slices are destroyed and it is prepared for LVM by writing an LVM header on it.

[Nikhil_1]

This is clear now. Thanks for your help!

With regards,
Nikhil