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Re: linux vs SAN



Do you have two physical machines that can see these disks? You referred
to HOST B, is there a HOST A, that is presented the same storage as well?

Thanks,

Tom Callahan
TESSCO Technologies
Desk: (410)-229-1361
Cell: (443)-506-6216
Email: callahant tessco com

A real engineer only resorts to documentation when the keyboard dents on the forehead get too noticeable.



baran yurdagul turkcell com tr wrote:

>Hi Tom,
>Thank you very much for the detail, it is really quite usefull but in
>our situation there are strange things happening. Just 10 minmutes ago
>when I type fdsik -l from Host B I have seen that 2 disks are active
>because the other disks cannot be read. I have created a partition  on
>sdd (sdd1) and make fs and label it. Afterwards I typed fdisk -l again
>to see the second active disk but I have been suprized that 4 disks seem
>to be accessiable now.. 
>Isn't it strange ? 
>Ps. :Do you have some documents ?
>
>-----Original Message-----
>From: redhat-list-bounces redhat com
>[mailto:redhat-list-bounces redhat com] On Behalf Of Tom Callahan
>Sent: Wednesday, February 01, 2006 3:46 PM
>To: General Red Hat Linux discussion list
>Subject: Re: linux vs SAN
>
>Welcome to Linux vs. the SAN. It's sometimes a tough road, but it's
>wonderful once it's working.
>
>We currently have several RHEL3 and RHEL4 systems booting and running
>exclusively off our SAN's, with no internal storage. We use Qlogic 2340
>HBA's, 2 in each system for High Availability. Our setups utilize two
>SAN cabinets, with MD software mirroring between the two SANs.
>
>Linux has multiple ways of dealing with the Active/Passive pathing
>issues of seeing 4 disks, when only two are presented. We currently use
>Qlogic's drivers which include "failover" support, this way the driver
>loads and all "passive" devices are not presented to the OS, only the
>actives. The card handles the occurrence of a path failure, and fails to
>the passive path, without the OS ever knowing (short of some entries in
>/var/log/messages).
>
>Multipathing is another option, but I am unsure of support in RHEL 2.1.
>There are tons of documents around the net on how to setup multipathing,
>including redhat's own documentation in their knowledgebase.
>
>Behavior you should see in an Active/Passive setup is below:
>1 - You have 2 disks presented from the SAN, one 10Gig and one 20Gig
>2 - Upon boot, you should see /dev/sda as 10Gig, /dev/sdb as 20Gig,
>/dev/sdc as 10Gig, and /dev/sdd as 20Gig (this could be reversed, with
>the 20Gig disk showing up first. it depends on the LUNs you have
>assigned the disks.)
>3 - if you `fdisk -l` each disk, you "should" have two disks come up
>with "unable to read from /dev/sdx", those are the passive disks.
>4 - When you are formatting/partitioning the disks, you will want to use
>the set of disks (set being /dev/sda,b and /dev/sdc,d) that you have
>determined are on the active controller path.
>5 - Make sure that when you format a disk, you are prepending a Label
>onto the disk(mkfs.ext3 -L/labelyouchose /dev/sdx or e2label /dev/sdx
>"/labelyouchose"), and use that Label for mounting in /etc/fstab
>(LABEL=/labelyouchose   /mountpoint   ext3   defaults   0 0)
>
>Again, without a multipathing or failover mechanism, things get very
>tricky when determining disks to use. I suggest using one of the above
>options, or if multipathing is not available, to upgrade to a newer
>release of RHEL.
>
>Thanks,
>
>Tom Callahan
>TESSCO Technologies
>Desk: (410)-229-1361
>Cell: (443)-506-6216
>Email: callahant tessco com
>
>A real engineer only resorts to documentation when the keyboard dents on
>the forehead get too noticeable.
>
>
>
>baran yurdagul turkcell com tr wrote:
>
>  
>
>>Hi All,
>>
>>
>>
>>I have connected my linux box to Hitachi SAN with 2 HBA. I have two
>>nodes and I want to use Veritas as cluster sw. When I wanted to make
>>partitioning and create filesystem on the disks I get a bit confused.
>>Because of 2 HBA, I have seen 4 disks (Infact I have two). I have
>>created a partition and make mkfs.ext3 on to it. But after mkfs.ext3 It
>>is strange that partitionin info has been flushed. Did you experience
>>such problem before or  is there any documentation or howto etc ?? 
>>
>>
>>
>>BR,
>>
>>
>>
>>
>>
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