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drbd-user: [DRBD-user] Does VMFS "play nice" with pri

[DRBD-user] Does VMFS "play nice" with primary/primary?

From: dbarker <dbarker_at_nospam>
Date: Sat Mar 13 2010 - 22:54:28 GMT
To: drbd-user@lists.linbit.com

I have two ESXi 4u1 servers.

Each has two DAS, sata, large disks; /dev/sdb and /dev/sdc.

Each has a vm running DRBD 8.3.7 under Debain 503 serving up the large disks
as /dev/drbd1 and /dev/drbd2. The disks are provisioned thin to the drbd
virtual machines.

Each drbd vm runs iscsi-target, serving the drbd block devices as LUN1 and
LUN2. The Type is set to blockio.

Each LUN is formatted in VMFS, and used by the various virtual machines. All
the virtual machines on ESXi0 are on LUN1 (on /dev/sdb), and all the virtual
machines on ESXi1 are on LUN2 (on /dev/sdc). So, I could easily change from
Primary/Primary to Primary/Secondary, but I thought that VMFS was a
clustering file system and would work properly with the Primary/Primary
setup. It certainly is an elegant and convenient setup.

The reason I ask is I had some strange errors today, like "Concurrent local
write detected!" and some scsi messages in ESXi's /var/log; including
hanging on of the ESXi, but they've all settled down and/or rolled off the
log. I probably caused these errors by improperly resizing my disks, but I
wanted to run this configuration past the group. I'd hate to run this way
for a few weeks and then discover I'd shot myself in the foot.

I can easily change one drbd vm to Primary/Secondary on /dev/drbd1 and the
other to Primary/Secondary on /devdrbd2. The only issue is the ease of
migration when failures occur. I like the elegance of the Primary/Primary
solution on both LUNs but will happily change if that's not the "right" way
to do this.

tia, Dan Barker

drbd conf:
========
global { usage-count yes; }

common { protocol C;
        handlers ... all the defaults from global.common.conf in 8.3.7 ... }

        net { allow-two-primaries; }

        syncer {
                csums-alg md5;
                rate 25M;
        }
}

resource r0 {
  startup { become-primary-on both; }
  device /dev/drbd1;
  disk /dev/sdb;
  meta-disk internal;
  on Storage00 {
    address 172.30.0.40:7789;
  }
  on Storage01 {
    address 172.30.0.41:7789;
  }
}

resource r1 {
  startup { become-primary-on both; }
  device /dev/drbd2;
  disk /dev/sdc;
  meta-disk internal;
  on Storage00 {
    address 172.30.0.40:7790;
  }
  on Storage01 {
    address 172.30.0.41:7790;
  }
}

ietd.conf:
=======
Target iqn.2010-03.com.visioncomm.Storage00:Storage00
Lun 0 Path=/dev/drbd1,Type=blockio,ScsiSN=SPIDSK-090311-00
Lun 1 Path=/dev/drbd2,Type=blockio,ScsiSN=SPIDSK-090312-00

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