LVM and VxVM Co-existence on 11i Systems

[Alzhy]

We are planning to migrate to Full VxVM (with Mirroring and FlashSnap) in light of our Heterogenous storage environment. I have made several tests last year with LVM managing the bootdisks and VxVM (3.5m) managing the rest. No issues whatsoever that I have encountered. Those of you that have VxVM implementations on 11i - are you aware of any known issues with this kind of implementation? We plan to:

1. Use LVM as is on our OS disks (mirrored)
2. Another pair of disks will be RootDG and will house one mirrored VOLUME that will serve as additional swap.
3. All the rest (SAN Storage - XP,EVA,HSG) will be VxVM diskgroups.


Any comments on this config? Or should I be better off just encapsulating my OS/Swap disks with VxVM and do away with LVM?

[Jeff Schussele · Accepted solution]

Hi Nelson,

All our systems that incorporate VxVM are of the type you list. OS on LVM (Mirror-UX & OnLine JFS, of course) & all else on VxVM. One note is that we deliberately carve a small LUN for rootdg as it's needs are not that great. We do setup up another larger LUN for secondary swap as we've had a case or two (ONLY out of quite a few dozen systems) where issues have been encountered on the rootdg VG that could have caused swap issues. We traced them back to a possible work error & a patch related issue. So we opted on the side of safety as a swap problem is almost always a panic.
One thing to stress is that IF you must use VxVM on any JBOD or ordinary disks - as opposed - to protected SAN arrays, then you definitely want to purchase the upgraded VxVM for the DMP (Dynamic Multi Pathing) feature that's not included in the Base 3.5 VxVM.

Rgds,
Jeff

[Alzhy]

Thanks Jeff.

So what specifically did you encounter having a SWAP volume on rootd? Any idea if the upcoming VxVM (4.1 I've heard) will already do away with a rootDG? Also, is it posible to have a slice of a disk be members of rootDG as it is possible on Solaris?

And what was the reason why you opted not to have VxVM manage your OS disks as well?

[Chris Huys_2]

> 1. Use LVM as is on our OS disks (mirrored)
> 2. Another pair of disks will be RootDG and will house one mirrored VOLUME that >will serve as additional swap.
> 3. All the rest (SAN Storage - XP,EVA,HSG) will be VxVM diskgroups.

I would say, go for VxVM totally. ;-)

VxVM mirrored bootdisks on internal disks on the host.
VxVM data disksgroups, located on luns of the san diskarray.

But if you keep, with the old and trusted LVM bootdisks. ;-), then create also the rootdg diskgroup on, mirrored internal disks on the host.

If youre adventurous and want to get rid of the internal bootdisks on the host, then I would say go for san (diskarray) (vxvm) bootdisks (if its supported on the diskarray side ... ). However in this case, I would make sure that the hba's on both the hostside as on the diskarray side, that are used by the sanbootdisk luns are different from the hba's that are used by the "non-boot datadiskgroup san (diskarray) luns".

Greetz,
Chris

[Alzhy]

Thanks Chris.

I opted to remain on LVM for the OS disks in order not to overhaul our procedures for OS recovery and DR.

I intend to mirror my rootdg and additionally have my additional swap volume on there. Since our systems employ dual DS2100/DS2110's (dual path as well) and 6 disks - I intend to put the other 4 on rootDG as 2 swapvols). If VxVM conks out.. then that means the entire system is unstable and so the argument that you endanger the system by having swap/dump on VxVM vols is no longer valid.

BTW.. have you had any serious issues with VxVM since you've used it on HP-UX 11i environments? Do you use extensive use of Mirroring (where it can do several resynchs simultaneously) and possibly FlashSnap?

[Chris Huys_2]

Hi Nelson,

> BTW.. have you had any serious issues
> with VxVM since you've used it on HP-UX
> 11i environments?

Never lost a serious amount of data, with vxvm, but it helps that most customers, that (can) buy the full license of vxvm, have all their volumes, (software/hardware) mirrored redundantly over 2 diskarrays. ;-)

Once, I lost a vxvm bootdisk and the vxvm mirrorbootdisk, but that was due to inexperience ( did some things in the wrong order in vxvm maintenance mode, i.e. didnt detach the plexes of the mirrored volume before booting from the primary bootdisk, in vxvm maintenance mode .. ) The ignite backup that was taken, of the rootdg diskgroup, saved the day. ;-)

> Do you use extensive
> use of Mirroring (where it can do several
> resynchs simultaneously) and possibly
> FlashSnap?

Not sure, what you mean with simultaniously resyncing. Most resynching, Ive seen up till now on the same diskgroup, seems to be pretty sequential. (volume after volume).

Flashsnap, I suppose you mean persistent fastresync and diskgroup split and join, yep, Ive seen it working on some customer sites. The(software) alternative to (hardware) business copy. ;-)

Greetz,
Chris

[Alzhy]

Chris...

The mirror synchs/resynchs on VxVM are sequential? I don'nt think so. This is precisely one of the reason why we are opting for VxVM becuase you can have several plex attaches (vxplex att) or FlashSnap (snapstart/snapbacks..) going on simultaneously.

Yeah I agree.. most VxVM disasters are due to inexperience. That is why on our boot disks -- we will remain with LVM.

Regarding FlashSnap.. the ability to mirror between arrays (dissimilar at that) is the compelling reason plus we've enough CPU cycles and I/O bandwidth anyway. We plan to mirror between XP and EVA environments... EVA LUNs will remain PATH managed by SecurePath whilst XP will be DMP .

[Steven E. Protter]

I recall some issues between Ignite and Vxvm back in 2002. Since we were not using VxVM at the time the solution center helped us remove VxVM.

There was a bug that made Ignite make_sys_image scripts fail and print or save manifest commands blow up causing script failures.

So. Test thoroughly. I imageine that was fixed since we're two versions of Ignite past that era. But as the Russsians say, Trust and Verify.

SEP

[Alzhy]

VxVM 3.5 appeared and tightly integrated (you don't have to use it or remove it) with the SEP2002 11i release. Back then - it already supported rootability - meaning you already have the option to let VxVM manage and mirror (for free) your OS disks.

But I suppose back then, Ignite-UX had some issues. Were it not for the CPQ-HP merger -- I'd bet the original plan of truly and fully supporting VxVM (and making it the preferred VM of HP-UX) would come earlier. I just think the decision by HP was a bright one -- the fact HP-UX has been using another Veritas Product - VxFS (aka JFS) since 1993..

Anyone installed the JUN2004 or (DEC2004) 11i v1.0 EOE (Enterprise) Update Release yet? I am curious if the bundled VxFS (oJFS) is already at 3.5

Thanks!

[Jeff Schussele]

Hi (again) Nelson,

Sorry for the delayed reply, I didn't see your post at first. Anyway, on to your questions...

1) We have an enterprise policy - even in LVM - that swap LVs will fly solo in a VG. So we haven't encountered specific issues, per se, but I've seen one LV screw up a VG to the point where the other LVs were inaccessible. I'd certainly hate for that to happen to swap LV.

2) I'm not sure about 4.1 - I've yet to read the release notes on it yet.

3) Currently 3.5 doesn't allow slices in HP-UX 11v1...BUT...the Itanium OS does allow slicing in LVM so VxVM for that OS may already allow this...but we don't have one so I can't confirm.

4) We use LVM for OS so we don't have to purchase the upgraded VxVM to get DMP. We always get the OS as Mission Critical or Enterprise so Mirror-UX & OnLineJFS are already included and LVM does alt links out of the box. Simply a cost-based decision.

Best Rgds,
Jeff

[Alzhy]

Jeff.. Thanks..

I'll just probably carve up small LUNS from our XP/EVA to serve as my rootDG in the meantime although I really see no issues/instabilities having rootdg contain a pair or 2 of SCSI disks and have 1 or more SWAP volume in them.

Those that already have some form of PATHING software ie. SecurePath on EVAs or AutoPath for XP arrays -- you don't need Ful VxVM. The Base VxVM will actually be sufficient already since you will not need any of the RAID or DMP features at all. Online shrinkage/increases is already supported with Base VxVM plus striping is already there..


BTW,

I just got confirmation from Veritas support that VxVM/VxFS 3.5 (aka Foundation Suite 3.5) will remain as is (no more upgrades?) on 11.11 (11i v1.0) environments. Storage Foundation 4.1 will be released on HP-UX 11i v 2.0 (11.23) environments I was told and this is sometime middle to Q3 of 2005 - probably to coincide with releases for Solaris, AIX , Windows and Linux environments. HP-UX 11.23 (PARISC/Itanic) with the Cluster VxVM/VxFS (MCOE?) probably Q3/Q5 of 2005.

[Chris Huys_2]

Hi Nelson,
> Chris...

> The mirror synchs/resynchs on VxVM are
> sequential? I don'nt think so.
Youre right. The resyncs of the volumes in the same diskgroup can be done in parallel.

Greetz,
Chris