 SAP HANA host fails in a distributed system, the standby host takes over the persistence of the failing host.
on the right, after the failure event.
Reservation to the devices and afterwards, the LUNs are mounted to the host.
Channel attached devices, which enables Host Auto-Failover on block storages.
storage directories which are found in /hana/data respectively /hana/log.
Files in /hana/shared as HANA binaries or runtime traces are still located on a shared file system like NFS.
The Fiber Channel Storage Connector is a ready to use implementation of SAP HANA’s Storage Connector API.
custom Storage Connector is outside the scope of this document.
configuration and mounting. A Storage Connector like the fcClient/fcClientLVM, implements this interface.
times. Releasing reservations and incautious mounting of LUNs can lead to severe damage and data loss!
reservation tool sg_persist directly works on the single paths.
more than one key registered, but only one key can be used for a reservation.
newest version of the fcClient/fcClientLVM, therefore only a few configuration steps have to be done.
Installation for more details. This is available since HANA SPS6.
further hosts. This way should not be used unless it is necessary due to problems during installation.
Connector, hdb_ha.fcClient or hdb_ha.fcClientLVM (SPS7) can be chosen.
o Param name: any parameter name for the Storage Connector.
Note: A double underscore (__) in front of <param name> must be used.
 The partition_[*]_[data|log]__wwid lines define the names of the LUNs to be used.
accessibility of the devices to other hosts. 6 denies external read and write access, 5 denies write only.
The default is 6. A detailed discussion on what type to use, can be found in Reservation Types.
above occur with type 6.
order to read metadata from it. The fcClientLVM does not work if the metadata is not accessible.
Additional information is available in SAP Note 1941776.
reservation type 6 (exclusive access), the only requirement is to set the following parameters for each LUN.
cause SAP HANA not to be able run.
the correct value (“features 0”), which might lead to confusion.
“queue”) in order to be less prone to errors on storage side.
For more information about multipath.conf settings, please contact your storage vendor.
/etc/sudoers file. The <sidadm> user must be able to issue the appropriate fencing and mounting commands.
read manually and put into the /etc/sudoers on all hosts for the SAP HANA <sidadm> user.
Partitions are not supported, i.e. the whole LUN must be formatted.
upper size limit of a plain LUN (typically 16 Terabyte) can be used for a single partition.
it is recommended to make the storage partition number a part of the volume group or logical volume name.
experience showed that XFS is used in general.
in Figure 1. The configuration for that scenario is found in the next section.
filesystem. Figure 2 shows an example of this configuration which was the only option prior to SPS10.
HANA SPS10 changed the default names of the failover groups to enable automatic failover of the DT hosts.
The failover groups are not changed when an upgrade to SPS10 or higher is performed.
installation of DT is described in the SAP HANA Dynamic Tiering: Installation Guide.
 The partition number for DT is defined to be in the range between 1024 and 2023.
The user-friendly mode to specify aliases instead of wwids is supported for DT as well.
global.ini which is meant for DT are ignored by the Storage Connector API if the parameter is set to “false”.
If a manual failover is initiated, the new DT worker requires access to the shared network path.
for that scenario is found in the next section.
 The partition number for AFA is defined to be in the range between 2048 and 3071.
The user-friendly mode to specify aliases instead of wwids is supported for AFA as well.
global.ini which is meant for AFA are ignored by the Storage Connector API if the parameter is set to “false”.
If a manual failover is initiated, the new AFA worker requires access to the shared network path.
with /some/path pointing to the directory, which contains the global.ini.
database. The /etc/sudoers file will be changed accordingly on all hosts if necessary.
Devices will be unmounted and reservation will be cleared when the host is removed.
SAP Note 2167727 for details about timeouts in hard or soft shutdowns.
Devices are not unmounted.
this host is already registered, it will be used.
Check that the key is actually registered.
Check if another host holds a reservation. If applicable, read the key <oldKey>.
Preempt the reservation from the other host. This is atomic.
fenced devices (“reservation conflict”).
hooks, which will be called during attach and detach.
The base classes can still be taken from the HANA installation leading to a simple file system structure.
Table: Possible errors that might occur and their solutions.
unable to find available device for writing SCSI-3 Registration or clearing of persistent reservation failed.
reboot of the server helps.
hostname01 kernel: [ 873.926030] sd 2:0:0:36: Reservations are not removed during HANA shutdown.
reservation conflict This avoids situations in which short running scripts (e.g.
hostname01 sudo: abcadm : TTY=unknown the corresponding idling HANA service.
out --register --param-sark=285436c3e178c43e not affect HANA startup.
API version 1.
Table: Typical use-cases that require manual intervention.
work on a LUN. released and no failover mechanism disrupts your planned work.
what you are doing – possible data loss.
after reboot. 6).
was not shut down gracefully, I cannot access some LUNs.
when trying to access the previously failed host.
stopped completely on all hosts.
I remove these?
Please make sure that HANA is stopped on all hosts.
thrown when accessing those devices.
shared resources will be revoked from it.
assigned waiting for failure of others to take over their role.
A Worker host is an active component accepting and processing requests.
An entity of server hardware that connects the host to the storage subsystem.
potentially without interrupting system use [source: Wikipedia].
registered keys, a device can be reserved, i.e., locked.
because the connection is broken between them.
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