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Boot disks in SAN

Fabio Ettore
Honored Contributor

Boot disks in SAN

Hello guys,

my question wishes some replies from your great experience on HP-UX systems.

What are issues to have boot disks (boot disk + mirror) in SAN (Storage Area Network)?

I think about a slow boot (slower than boot disks inside the machine) and performance issues on network.
It also could be another point of failure for Disk Array.

Other hints according to your experience?

Thanks and best regards,
Ettore
WISH? IMPROVEMENT!
27 REPLIES
Mark Grant
Honored Contributor

Re: Boot disks in SAN

I haven't done this and I understand it is quite a new facility. However, in my opinion, I would much much prefer to have a local disk to boot off. If your machine isn't attached to the SAN, you can't boot it. I admit if all your data is on the SAN annd the SAN isn't available there isn't much point in booting it but I just like being able to boot.
Never preceed any demonstration with anything more predictive than "watch this"
G. Vrijhoeven
Honored Contributor

Re: Boot disks in SAN

Ettore,

Same here, no experience. It can be usefull if you have more than one identical server in case of desaster recovery.
I would prefer local disks for swap.

HTH,

Gideon
Roberto Polli
Trusted Contributor

Re: Boot disks in SAN

Using fiber there should be less network speed issues.
Maybe the whole network could be a point of failure (eg: cables, NIC)
You may want to implement a redundant boot nic.
eg.

MirroredDiskArray
| |
| |
Controller1-Controller2
| \ / |
| \/ |
| /\ |
| / \ |
SANswitch1 SANswitch2
| |
| |
NIC1 NIC2
| |
Server


Any comments are welcome.


Peace, R>

Roberto Polli
Trusted Contributor

Re: Boot disks in SAN

these f*ing html blew up spaces from my diag but it should be readable.

Swap space issues are meaningful but you may use local swap.

Maybe you can have problems upgrading NIC firmware or nic driver. Don't know how is singel-user booting tru san-storage but the server should see the fiber like a scsi device (but I'm not sure about it!!!)
Peace ,r
Uwe Zessin
Honored Contributor

Re: Boot disks in SAN

For some systems (like Windows) one puts the system disk onto the SAN so that it can be replicated by the storage array to a desaster recovery site where an identical spare server is located.

Running the system disks on the SAN is a hot topic for OpenVMS and Tru64 Unix systems, because both can use a common system disk within a cluster. It is less of a problem, because the AlphaServer console has good boot support and diagnostic tools.

It limits the system management a little bit, because patches are rolled out only once. The downside, of course is, that you are now depended on one copy of the system disk, but we all know that breakfast is not free ;-)

You could use value-added services on the storage array like snapshots or clones to protect your data or make it available for tests. Not every operating system has a powerful volume manager.

A local disk with a pre-installed operating system and up-to-date drivers is still a nice thing. It adds additional diagnostics for some systems and you don't have to pull your system up from CD-ROM - I have seen cases where the drivers on the CD-ROM were too old and I could no longer access a storage array with recent firmware.


Roberto,
if you attach your drawing as a .TXT file there is less reason to curse ;-)
.
harry d brown jr
Honored Contributor

Re: Boot disks in SAN

We have over 200 "systems" booting from the SAN, basically because we have over 200 virtual partitions across 50 N-class servers. Some older equip (like K's) didn't work, so we scrapped them from booting off the SAN.

You need to check with your SAN switch, SAN disk, and server providers to determine the interoperibility issues.

live free or die
harry
Live Free or Die
Zinky
Honored Contributor

Re: Boot disks in SAN

Ettore,

I am currently prototyping SecurePath 3.0D - which has support for boot,swap and dump on SAN devices(including EVA). Despite it being withdrawn twice already, I am finding it remarkably robust and fast too. We will be rolling it to production very soon once we get an Okay from HP on SecurePath 3.0D being once more on G.A.

Harry,

What SAN environment are you booting off your servers? DO you use SecurePath/AutoPath or simply PV links?


Thanks!



Hakuna Matata

Favourite Toy:
AMD Athlon II X6 1090T 6-core, 16GB RAM, 12TB ZFS RAIDZ-2 Storage. Linux Centos 5.6 running KVM Hypervisor. Virtual Machines: Ubuntu, Mint, Solaris 10, Windows 7 Professional, Windows XP Pro, Windows Server 2008R2, DOS 6.22, OpenFiler
harry d brown jr
Honored Contributor

Re: Boot disks in SAN

Nelson,

emc/McData switches with EMC symm's and clariions.

live free or die
harry
Live Free or Die
Zinky
Honored Contributor

Re: Boot disks in SAN

Harry,

And HP "supports" this environment?

I suppose you use PVLINKS for Path protection?
Hakuna Matata

Favourite Toy:
AMD Athlon II X6 1090T 6-core, 16GB RAM, 12TB ZFS RAIDZ-2 Storage. Linux Centos 5.6 running KVM Hypervisor. Virtual Machines: Ubuntu, Mint, Solaris 10, Windows 7 Professional, Windows XP Pro, Windows Server 2008R2, DOS 6.22, OpenFiler
Emilio Brusa
Frequent Advisor

Re: Boot disks in SAN

Although you can have the boot disks inside the SAN,I would prefer to boot from internal disks. because the SAN could have depending of your configuration more points of failure.
Before choice SAN you should revise your San enviroment to see the possible points of failure. (switch,disk,etc..)

E.
Zinky
Honored Contributor

Re: Boot disks in SAN

Well we will possibly be "brave" enough to proceeed since we have a redundant SAN... Half the SAN components, HBA's, Cabling, Core Switches can be allowed to fail. Of course Disk arrays are not supposed to Fail ;-)
Hakuna Matata

Favourite Toy:
AMD Athlon II X6 1090T 6-core, 16GB RAM, 12TB ZFS RAIDZ-2 Storage. Linux Centos 5.6 running KVM Hypervisor. Virtual Machines: Ubuntu, Mint, Solaris 10, Windows 7 Professional, Windows XP Pro, Windows Server 2008R2, DOS 6.22, OpenFiler
Uwe Zessin
Honored Contributor

Re: Boot disks in SAN

Just don't tell that the disk arrays ;-)
.
Fabio Ettore
Honored Contributor

Re: Boot disks in SAN

Good morning guys.

Nelson,
I agree with you about redundanted environment. Of course with good attention boot disks in SAN is possibile and it works.
Even, from your words and descriptions, it seems that boot disks in SAN is better than boot disks inside the machine!
Really do you think this?

Altogether I agree with Uwe about his first post. He talked about Tru64; Trucluster on Tru64 (and maybe in future on HP-UX!) works in a way that all disks are shared (boot disks too). That is a functionality of Trucluster and (of course) is not a problem to share boot disks (even about that I can be critic!).
But on HP-UX Service Guard just shares data disks.
Definitively I think that it is not a good idea to configure boot disks in SAN (thus shared boot disks). Even redundanted environment has too many points of failure. Also (not as last) the thought that anyone handles Disk Array (for example to configure volume groups on other HP-UX systems attached to Disk Array) can harm my boot disks.

The only one advantage to configure boot disks in SAN is economic side. Is it worth to do that?

Best regards,
Ettore
WISH? IMPROVEMENT!
Uwe Zessin
Honored Contributor

Re: Boot disks in SAN

Ettore,

OpenVMS and Tru64 Unix require a separate license to enable mirroring. It is just a question if you buy a license for each server -or- a separate backplane RAID controller to mirror your boot disks -or- use the mirror functionality of your SAN-based storage array that you already have paid for.

How is this on HP-UX? I can't really say I have experience with it, but following the forums it sounds like LVM is 'standard'.


Allow me a small correction? OpenVMS allows booting multiple cluster memebers from one single shared system disk per hardware architecture - in a Tru64 Unix cluster each member needs a small boot disk containing the kernel and configuration data, the remainder it then on one common disk.
.
Fabio Ettore
Honored Contributor

Re: Boot disks in SAN

Uwe,

yes, LVM is standard, mirror needs a license on HP-UX too.

Thanks for your explanation about OpenVMS and Tru64; corrections/clarifications always are welcome! :-)

Best regards,
Ettore
WISH? IMPROVEMENT!
Emilio Brusa
Frequent Advisor

Re: Boot disks in SAN

Ettore.
The new machines like rp8420,rp3410 with enterpise OE, include the mirror license now.

E.
Fabio Ettore
Honored Contributor

Re: Boot disks in SAN

Hi Emilio,

are you sure about that?
I think that mirror license has to be purchased apart. If you have a machine where mirror is already installed (with license) then I think that HP configured it for you but normally it is not so.

Otherwise can you provide a document or anything to sustain your information?

Thanks and best regards,
Ettore
WISH? IMPROVEMENT!
Zinky
Honored Contributor

Re: Boot disks in SAN

HPUX Enterprise OE includes:

Online JFS (aka Full VxFS)
GlancePlus Pak
HPOV Performance Agents (aka MeasureWare)
MirrorDisk/UX

Plus of course the base Veritas Volume Manager 3.5m -- that comes with Free Mirroring but only on rootDG.

But if your Bootdisk (on a SAN) is already a protected LUN (ie. RAID5 or RAID10 on your SAN Array) -- why bother with MirrorDisk/UX?



Hakuna Matata

Favourite Toy:
AMD Athlon II X6 1090T 6-core, 16GB RAM, 12TB ZFS RAIDZ-2 Storage. Linux Centos 5.6 running KVM Hypervisor. Virtual Machines: Ubuntu, Mint, Solaris 10, Windows 7 Professional, Windows XP Pro, Windows Server 2008R2, DOS 6.22, OpenFiler
Fabio Ettore
Honored Contributor

Re: Boot disks in SAN

Hi everybody,

it is important to clear all things:

Emilio,
you said:
>The new machines like rp8420,rp3410 with enterpise OE, include the mirror license now.

It is exact for an half: MirrorDisk/UX is bundled (of course with license) in OS HP-UX Enterprise OE for the version 11.11.
Anyway MirrorDisk/UX doesn't depend on model of machine (like rp8420,rp3410).
Then if you say that

'The new machines like rp8420,rp3410 with enterpise OE, include the mirror license now.'

it is important to specify the version of HP-UX and (of course) Operating Environment.


Nelson,
question was submitted from Uwe. It is not about my problem. You can find the question of Uwe above.
Anyway when you said

'HPUX Enterprise OE includes:

Online JFS (aka Full VxFS)
GlancePlus Pak
HPOV Performance Agents (aka MeasureWare)
MirrorDisk/UX'

it is right as for Emilio but it is the truth for HP-UX 11.11 no 11.00.
Also: MirrorDisk/UX is bundled in that Operating Environment, that is Enterprise OE, not in other OEs. Infact in 11.11 was introduced a new hierarchy of Operating Environment (the following is valid for servers):

HP-UX 11i Base OE

HP-UX 11i Internet OE, bundled with it:
°Unlimited user licenses,Web QoS,JavaVM,Apache websvr,E-speak,Ignite-UX,All networking drivers,EMS,LDAP.

HP-UX 11i Enterprise OE, it is Internet OE plus the following applications:
°PRM,MirrorDisk/UX,OnLineJFS,GlancePlus,HA Monitors.

HP-UX 11i Mission Critical OE, it is Enterprise and Internet OEs plus the following applications:
°MC/ServiceGuard,WLM


CONCLUSION:
MirrorDisk/UX with its license is included in HP-UX 11i Enterprise OE or higher OE, no in base or Internet OE.

Therefore your affirmations are good for an half because it is important to specify which HP-UX version and which Operating Environment we are talking about.

Hope this clarifies all doubts.
Welcome will be other informations.

Best regards,
WISH? IMPROVEMENT!
Uwe Zessin
Honored Contributor

Re: Boot disks in SAN

Zinky
Honored Contributor

Re: Boot disks in SAN

Uwe.. thanks for the update.

'Been awaiting this announcement since it was withdrawn several times in the past...
Hakuna Matata

Favourite Toy:
AMD Athlon II X6 1090T 6-core, 16GB RAM, 12TB ZFS RAIDZ-2 Storage. Linux Centos 5.6 running KVM Hypervisor. Virtual Machines: Ubuntu, Mint, Solaris 10, Windows 7 Professional, Windows XP Pro, Windows Server 2008R2, DOS 6.22, OpenFiler
harry d brown jr
Honored Contributor

Re: Boot disks in SAN

Nelson,

Yes, HP and EMC support this. We are running about 200 virtual partitions across ~50 n-class servers, that use the SAN for booting and other VG's.

EMC doesn't currently support booting across ISL's, but we expect them to bless it sometime in the future, especially since their lab does it without issues. We do keep boot ports/paths separate from data vg's.

live free or die
harry
Live Free or Die
Uwe Zessin
Honored Contributor

Re: Boot disks in SAN

Good point, Harry.
In MicroSoft Cluster configuration it used to be mandatory to have a different adapter for the boot LUN than for the cluster shared LUNs. I thought that has changed, but the current boot guide from February 2004 still lists this requirement.

On AlphaServers there never was such a restriction.
.
Zinky
Honored Contributor

Re: Boot disks in SAN

So Harry, each of your N-Class' vPar would have 4 FC-HBA's? Why the need for separate boot paths (FC channels) for your SAN based boot disks?
Hakuna Matata

Favourite Toy:
AMD Athlon II X6 1090T 6-core, 16GB RAM, 12TB ZFS RAIDZ-2 Storage. Linux Centos 5.6 running KVM Hypervisor. Virtual Machines: Ubuntu, Mint, Solaris 10, Windows 7 Professional, Windows XP Pro, Windows Server 2008R2, DOS 6.22, OpenFiler