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Boot via SAN
Hello People,
I´ve been configuring 11 servers with Boot of System Operation (LUN) inside of Clariion.
Each server can access it own LUN (boot) only a Path, I mean ==> 1 Server => 1 CNA/HBA => 1 Port SW-SAN 1 => 1 SPA (Clariion).
Of course if my Switch and SPA comes down, my server will became down too. So I am without HA to my disk of boot...., I am thinking to put another CNA/HBA ==> 1 Port SW- SAN 2 and to do the zoning with SPB (Clariion).
In this case I guess that my server will be access 2 disk. I used to install Power Path just to Data Disk and not Boot Disk.
How Can I configure HA to my boot disk, to avoid unavailability of my servers?
Thanks
Fabricio
dynamox
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2 Intern
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20.4K Posts
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January 28th, 2011 11:00
PowerPath will detect the failure and redirect all disk access through the other HBAs that's connected SW SAN 2.
Fabricio1
19 Posts
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January 28th, 2011 11:00
OK,
But in this case PowerPath to Boot disk works?
Let supose, my System Operacion is up via boot disk SW SAN 1 and SPA.
If my SW SAN 1 comes down? How Does Power Path will be works?
dynamox
2 Intern
2 Intern
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20.4K Posts
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January 28th, 2011 11:00
you need to install PowerPath regardless, each HBA needs to be zoned to SPA and SPB and configured in the BIOS as well.
Fabricio1
19 Posts
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January 28th, 2011 12:00
OK,
I understood, but I have 2 doubts.
1-) We are talking aboout (LUN) boot disk, You said that PowerPath will be redirect all connection to second HBA . In this case I am assuming that my System Operation does not coming down? The server will be avaliable to all users, 0% down time? Is that correct?
2-) Are there two kinds of PowerPath.
a-) Free - Only redundant between HBA (1 / 2)
b-) Payed - redundant and load balance between HBA (1 / 2).
Could I use a-) Option (free PP) only redundant ?
Thank you
Fabricio
Fabricio1
19 Posts
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January 28th, 2011 13:00
OK Glen,
My main doubts is know how PP will be working with (Lun - Boot) case the path active becames down. Will be the server works?
Because I have to take decision about this, because the SLA of my enveriroment is high.
Fabricio1
19 Posts
0
January 28th, 2011 13:00
OK,
I understood, but I have 2 doubts.
1-) We are talking aboout (LUN) boot disk, You said that PowerPath will be redirect all connection to second HBA . In this case I am assuming that my System Operation does not coming down? The server will be avaliable to all users, 0% down time? Is that correct?
2-) Are there two kinds of PowerPath.
a-) Free - Only redundant between HBA (1 / 2)
b-) Payed - redundant and load balance between HBA (1 / 2).
Could I use a-) Option (free PP) only redundant ?
Thank you
Fabricio
kelleg
4.5K Posts
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January 28th, 2011 13:00
PowerPath when installed on the host will provide fialover protestion to all the LUN's owned by the host. It does not know about boot-fron-san as PowerPath is not loaded until the OS boots. If you have one HBA in the host and two paths to the array - one to SPA and one to SPB, then if one path fails, PowerPath will failover to the surviving path. Best is to have two HBA's for best protection.
For boot-from-san, you can configure the HBA's with two paths - not sure how you do this, but this is a HBA function in the bootROM. I believe that you need two physical HBA's for this to work.
glen
kelleg
4.5K Posts
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January 28th, 2011 14:00
When the host boots and the OS loads, PowerPath will start up. If, for example, the boot LUN (say the boot LUN is owned by SPA) will show as the C:. If you have two paths from the HBA - one path to SPA and one path to SPB PowerPath will see that LUN on SPA and provide failover. If the on SPA path from the HBA to the LUN that is the boot LUN fails, PowerPath will switch the path to SPB. This mantains access to the LUN. If you reboot the host before the path is fixed, the HBA will not see the LUN as it is now owned by the other SP. If the HBA fails (and you have only one HBA) then you will lose all access to the LUN.
HBA1 <--> SPA0
HBA2 <--> SPB1
HBA2 <--> SPA0
HBA1 <--> SPB1
Best Practice recommends two HBAs and four paths. This requires licensed (payed) PowerPath. Basic PowerPath supports one HBA and two paths. If you received PowerPath from DELL, that version supports two HBA, but only a single path per HBA.
glen
tkjoffs
159 Posts
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January 30th, 2011 19:00
Please allow me to clarify:
Hopefully that helps.
TJ
RRR
2 Intern
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5.7K Posts
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January 31st, 2011 04:00
I was just about to write something about redundancy BEFORE the operating system is up and running (and PPath as well). In the BIOS of each HBA you'll have to put the boot-LUN. the controller order in the server's BIOS will now make sure the first controller with a LUN 0 will be used to boot from.
Fabricio1
19 Posts
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January 31st, 2011 05:00
I appreciate all answers above, but my environment has the follow configuration.
1-) Server (UCS - Cisco) - 2 CNA.
2-) SW - SAN - MDS 9124
3-) Storage - CX480
Now, my System Operation is running by boot via SAN through CNA1 on SW-SAN1 - SPA1. I can do the configuration in CNA2 on SW-SAN2 - SP2 + Zoning and from BIOS my UCS recognize the second way.
The great doubts is to know if PP will be able deal with case any device (CNA1 / SW-SAN1 / SPA1) fail, the server continues works without restart or something like that. Because that is possible to do the second way, but I need to know if will work.
Does Someone understand my problem ?
Thank you
RRR
2 Intern
2 Intern
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5.7K Posts
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January 31st, 2011 06:00
2 HBAs with an OS up and running: you'll need a licenced PowerPath to be able to deal with path failover involving 2 HBAs.
tkjoffs
159 Posts
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January 31st, 2011 18:00
Do this: "I can do the configuration in CNA2 on SW-SAN2 - SP2 + Zoning and from BIOS my UCS recognize the second way." and it will work fine. PowerPath will do it's thing and you will be happy (paid version - you need the paid version). Don't do that, and you won't be happy.