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Supported Kdump Targets

This document try to list all supported kdump targets, and those supported
or unknown/tech-preview targets, this can help users to decide whether a dump
solution is available.

Dump Target support status
==========================
This section tries to come up with some kind of guidelines in terms of
what dump targets are supported/not supported. Whatever is listed here
is not binding in any manner. It is just sharing of current understanding
and if something is not right, this section needs to be edited.

Following are 3 lists. First one contains supported targets. These are
generic configurations which should work and some configuration most
likely has worked in testing. Second list is known unsupported targets.
These targets we know either don't work or we don't support. And third
list is unknown/tech-preview. We either don't yet know the status of kdump
on these targets or these are under tech-preview.

Note, these lists are not set in stone and can be changed at any point of
time. Also these lists might not be complete. We will add/remove items to
it as we get more testing information. Also, there are many corner cases
which can't possibly be listed. For example in general we might be
supporting software iscsi but there might be some configurations of it
which don't work.

So if any target is listed in supported section, it does not mean it works
in all possible configurations. It just means that in common configurations
it should work but there can be issues with particular configurations which
are not supported. As we come to know of particular issues, we will keep on
updating lists accordingly.

Supported Dump targets
----------------------
storage:
        LVM volume
        Thin provisioning volume
        FC disks (qla2xxx, lpfc, bnx2fc, bfa)
        software initiator based iSCSI
        software RAID (mdraid)
        hardware RAID (cciss, hpsa, megaraid_sas, mpt2sas, aacraid)
        SCSI/SATA disks
        iSCSI HBA (all offload)
        hardware FCoE (qla2xxx, lpfc)
        software FCoE (bnx2fc) (Extra configuration required,
            please read "Note on FCoE" section below)

network:
        Hardware using kernel modules: (tg3, igb, ixgbe, sfc, e1000e, bna,
              cnic, netxen_nic, qlge, bnx2x, bnx, qlcnic, be2net, enic,
              virtio-net, ixgbevf, igbvf)
        protocol: ipv4
        bonding
        vlan
        bridge
        team
        vlan tagged bonding
        bridge over bond/team/vlan

hypervisor:
        kvm
        xen (Supported in select configurations only)

filesystem:
        ext[234]
        xfs
        nfs

firmware:
        BIOS
        UEFI

hypervisor:
        VMWare ESXi 4.1 and 5.1
        Hyper-V 2012 R2 (RHEL Gen1 UP Guest only)

Unsupported Dump targets
------------------------
storage:
        BIOS RAID
        Software iSCSI with iBFT (bnx2i, cxgb3i, cxgb4i)
        Software iSCSI with hybrid (be2iscsi)
        FCoE
        legacy IDE
        glusterfs
        gfs2/clvm/halvm

network:
        hardware using kernel modules: (sfc SRIOV, cxgb4vf, pch_gbe)
        protocol: ipv6
        wireless
        Infiniband (IB)
        vlan over bridge/team

filesystem:
        btrfs

Unknown/tech-preview
--------------------
storage:
        PCI Express based SSDs

hypervisor:
        Hyper-V 2008
        Hyper-V 2012

Note on FCoE
=====================
If you are trying to dump to a software FCoE target, you may encounter OOM
issue, because some software FCoE requires more memory to work. In such case,
you may need to increase the kdump reserved memory size in "crashkernel="
kernel parameter.

By default, RHEL systems have "crashkernel=auto" in kernel boot arguments.
The auto reserved memory size is designed to balance the coverage of use cases
and an acceptable memory overhead, so not every use case could fit in, software
FCoE is one of the case.

For hardware FCoE, kdump should work naturally as firmware will do the
initialization job. The capture kernel and kdump tools will run just fine.

Useful Links
============
[1] RHEL6: Enabling kdump for full-virt (HVM) Xen DomU
    (https://access.redhat.com/knowledge/solutions/92943)

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