How To
Summary
Distributed Replicated Block Device (DRBD) is an open source distribution for replicated storage on the Linux platform. DRBD layers logical block devices over existing logical block devices on participating cluster nodes. Writes to the primary node are transferred to the lower-level block device and simultaneously propagated to the secondary node.
When HA is enabled, the /store file system on the QRadar appliance peers (primary and secondary) is replicated using the drbd feature. Every write request to /store, is replicated and written to the secondary peer node in real time, and then the write request "completes" and control is passed back to the Linux kernel. This is called a "synchronous mode" replication. This disk replication is run over the management interface (normally eth0) unless the system is configured with a crossover connection using another LAN interface. When a node is detected to be out of sync, data is automatically synchronized from the other node.
Objective
cat /proc/drbd
cat /sys/kernel/debug/drbd/resources/store/connections/<hostname>/0/proc_drbd
<hostname>
with your system's hostname or use an asterisk (*
) in place of <hostname>
Environment
Steps
cat /proc/drbd
version: 8.4.11-1 (api:1/proto:86-101)
GIT-hash: 66145a308421e9c124ec391a7848ac20203bb03c build by vagrant@rhel7.localdomain, 2020-10-09 13:46:53
0: cs:WFConnection ro:Primary/Unknown ds:UpToDate/DUnknown C r-----
ns:211359746 nr:2718712 dw:63591809 dr:864686747 al:472794 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:d oos:137219716
cat /sys/kernel/debug/drbd/resources/store/connections/*/0/proc_drbd
0: cs:Established ro:Primary/Secondary ds:UpToDate/UpToDate C r-----
ns:169002070 nr:569514849 dw:733548027 dr:20516751 al:12473 bm:802359 lo:0 pe:[17;0] ua:0 ap:[17;0] ep:1 wo:1 oos:0
act_log: used:7/1237 hits:495991 misses:251891 starving:0 locked:0 changed:51682
blocked on activity log: 0/0/0
cs | Connection State |
ds | Disk State |
ro | Resource Role |
Connection State
Value | Interpretation |
Connected | A DRBD connection has been established, data mirroring is now active. This is the normal state. |
Standalone | No remote node configuration available. The remote node has not yet been connected, or has been deliberately disconnected or has dropped its connection due to failed authentication or a split-brain situation. |
WFConnection | The local node is waiting until the remote node starts responding to communication requests from the local node. |
SyncSource | Synchronization is currently running, with the local node being the source of synchronization. |
SyncTarget | Synchronization is currently running, with the local node being the target of synchronization. |
- If HA has been configured and the local node has Connection State set to Standalone
- If the remote node is operational but the connection status is WFConnection
Disk State
Value | Interpretation |
Diskless | DRBD is facing issues accessing the disk. |
Failed | Lower level I/O issues when accessing the disk. |
Negotiating | Disk is getting connected to DRBD. |
Inconsistent |
The data on the disk is inconsistent and not usable.
This status is usually found on the secondary HA host when it is added and when the initial full synchronization of data from the primary HA host is being done.
|
Outdated |
The data on the disk is consistent (and usable) but outdated when compared to the other node.
This status can be seen on the secondary HA host when it goes offline for a bit and comes back online.
|
DUnknown | This state is used for the remote disk if no network connection is available. |
Consistent | Consistency of data on a node without a connection. When the connection is established, it is decided whether the data on the node is UpToDate or Outdated. |
UpToDate | Consistent, up-to-date state of the data. This is the normal state. |
cat /proc/drbd
version: 8.4.11-1 (api:1/proto:86-101)
GIT-hash: 66145a308421e9c124ec391a7848ac20203bb03c build by vagrant@rhel7.localdomain, 2020-10-09 13:46:53
0: cs:WFConnection ro:Primary/Unknown ds:UpToDate/DUnknown C r-----
ns:211359746 nr:2718712 dw:63591809 dr:864686747 al:472794 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:d oos:137219716
ds:UpToDate/DUnknown
Resource Role
Value | Interpretation |
Primary |
The resource is currently in the primary role, and maybe read from and written to. This role only occurs in one of the two nodes.
|
Secondary |
The resource is currently in the secondary role. It normally receives updates from its peer (unless running in disconnected mode), but may neither be read from nor written to.
|
Unknown | The resource’s role is currently unknown. The local resource role never has this status. It is only displayed for the peer’s resource role, and only in disconnected mode. |
The words LINSTOR®, DRBD®, LINBIT®, and the logo LINSTOR®, DRBD®, and LINBIT® are trademarks or registered trademarks of LINBIT in Austria, the United States and other countries.
Document Location
Worldwide
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Document Information
Modified date:
19 July 2024
UID
ibm16420029