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need help on boot on san for rhel

Posted on 2014-03-17
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Last Modified: 2014-03-25
Hi All,

Could you help with best solution in detail for Boot on SAN in which OS will be RHEL ?

I also need to know what all pre requisite needed to confiugre that from OS and Storage side?

Please need urgent help on that with steps to configure it!

Highly appreciated  
Thanks
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Question by:apunkabollywood
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by:arnold
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Boot from SAN meaning no disk in the system, diskless?
PXE BOOT SERVER THAT will have the image that will get the initial bootup process going after which point the iscsi/FC a transition bootup process will start.

Which HBA do you have?
http://filedownloads.qlogic.com/files/driver/65636/readme_ddkit_redhat.pdf

For iscsi there are other
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by:Daniel Helgenberger
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Most FC/SAS HBAs and newer Network cards do support booting via their bios directly; meaning you do not need to have a disk installed or use PXE.
Newer network cards sometimes have an iSCSI initiator build in; you can configure it on machine boot up. RHEL does support these in their installer via the 'advanced storage' option.

We need to know more about your setup though: what hardware; witch controller: iSCSI; FCoE; SAS/FC.
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by:apunkabollywood
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Thank you All for your suggestions.

Actually i need to setup a one - Can you suggest what best hardware should I go for this solution with RHEL 6  and brand should be HP DL series.

I am new to this technology so help will be needed.

Thanks.
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by:andyalder
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There is a link here to download the boot from SAN configuration guide. http://h18000.www1.hp.com/storage/networking/bootsan.html
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by:apunkabollywood
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Thanks but I also want to make sure what all we need to do from OS side - like we have RHEL 6?
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by:apunkabollywood
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Also what you would suggest as our core task to restore our database server quickly - please advice if some better solutions available or this would work fine?

Please suggest from both side RHEL OS and SAN
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by:Gerald Connolly
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You don't have to do much at all, just follow the setup guide and the system should boot like it would from a local disk. It doesn't know it's booting off the SAN. I first did this in the late 90s, it took a while to sort it, but once done it worked a treat
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by:Daniel Helgenberger
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Actually i need to setup a one - Can you suggest what best hardware should I go for this solution with RHEL 6  and brand should be HP DL series.

I am new to this technology so help will be needed.

Because you say you are new I like to list some fundamental things, (broken down and in no way complete):

- A SAN is - like an LAN network - switchable (switched fabric with point to point connections). It is transmitting storage data (frames) rather than  rather than packets (ip). The SAN is generally optimized for layer2 switching (ethernet equivalent) and therefore has much less protocol overhead.

- A quasi standard (I do not see anything else much used) is the SCSI protocol

- There are three main 'flavors': Fibre Channel (FC) and Serial Attached SCSI (SAS), TCP/IP-SCSI (iSCSI). All of them use different transport methods: FC uses fibre optical, SAS copper, iSCSI uses SCSI encapsulated in TCP/IP (which in turn is transported over copper or fibre).

- While classic FC and SAS use their own hardware (switches, HBA's) IP - based iSCSI can use (the usually already present) network hardware and switches. It can therefore even be routed (layer3). This comes at a cost, iSCSI is slower and - often more importantly - has much higher latencies (= fewer IOPS).

- There is another option, Fibre Channel over Ethernet (FCoE). It transports native fibre channel frames over ethernet. This is considered as the 'best' way if you build systems from a scratch now (and have the money to spend) as it uses the same cabling, switches and HBA's for classical network as well as Fibre Channel frames (this is called converged networking). The advantage: Much better SAN performance, lower administrative overhead (single point of administration, FCoE behaves like VLANs on classical switches).

- Then, some people call it a SAN if you not only have switched fabric storage, but if also you have a file system capable of handling multi - node storage access (that is, everybody can read and write at the same time to the same storage clustered filesystem).

Ignore the last point for your setup. As a boot volume, you will always provision a single exclusive LUN per bare metal / virtual machine.

To give you some recommendations on hardware, you have to figure out the transport first.
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by:Gerald Connolly
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- A quasi standard (I do not see anything else much used) is the SCSI protocol

A quasi standard? Where do you get that from, SCSI is the standard that is used for all disk access
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by:andyalder
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He means that at FC4 layer it's always SCSI that's encapsulated, nobody uses IP over Fibre Channel nor any other protocol but SCSI although Brocade let you set FC IP address. Makes me wonder if you could run IP instead of SCSI over FCoE just for a laugh.
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by:Gerald Connolly
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The original spec had SCSI, IP, HIPPI and ATM? I think
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by:andyalder
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I do believe you're right and indeed Ethernet with whatever it's carrying inside it can go over FC, however you get into the ATM over FC over ATM scenario again.

www.mskl.de/CONTENT/PDF/Basics_of_Fibre_Channel.pdf
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by:Daniel Helgenberger
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SCSI is the standard that is used for all disk access

Of course there is ATA, which is not SCSI. Even Serial ATA is not SCSI. Further, there are still floppy drives around, also not SCSI. I can continue with Flash based storage like MMC and CF, but I think I made my point.
SCSI is the most widely spread standard for disk access, but not the standard for accessing disks; thats what I meant with quasi standard. As I said above, my post is broken down and in no way complete or exact in details I like to add here.

But please, lets stick to the topic here. The asker said he is new to SANs; and that I wanted to provide, a starting point for for someone new to the topic. This means for me only technology and protocols actually used.
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by:apunkabollywood
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Thanks all for your detailed info and advice - now i understood a lot - just last thing to make sure - There is no thing need to do from OS prespective - ALL things need to be done from Storage side and some from Hardware side ? Please confirm the same?
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Daniel Helgenberger earned 500 total points
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There is no thing need to do from OS prespective
Not quite. This largely depends what you mean. The Controller has it's OS too, but suppose you did not mean that ;).

As with all the protocols mentioned you need OS support for them. A FC HBA needs drivers (in linux, these are most likely 'build in'). iSCSI needs an OS side initiator. Also, if you have multiple paths to the target LUN you need some kind of multipath driver (dm-multipath in Linux, MIPO in Windows).
Also, I mentioned a shared storage, where you mount your LUN with read/write on multiple nodes. This requires a special filesystem. Further it becomes more complicated if you want to support heterogeneous operating system networks - there are only a handful of commercial solutions left in this case (for instance, Quantum StorNext being the most stable IMHO, no advertising here - we use it since some seven years now and it never let me down).

Bottom line, you need to be able to access the LUN on the client site in some way. And this way might be quite different from normal direct attached storage. For instance, iSCSI alone requires a good deal of expertise to deploy LUNs that are fast, secure and fool proof. On the other hand, Fibre Channel is much easier to handle; but more complex on the hardware site (cabling, switches, HBA's). This is why I said FCoE being the 'royal road' in new deployments - though I suspect that some experts will disagree :)

As for the rest, provisioning the LUNs, adding storage, extending storage, storage paths, FC zoning ect pp. will be done at the controller's side.
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by:apunkabollywood
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thanks daniel for your help - appreciated
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by:andyalder
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Wish I could remove the link to the boot from SAN configuration guide.
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