Caveats for a Collector Group with Multiple Log Collectors
Table of Contents
Caveats for a Collector Group with Multiple Log Collectors
You can Configure
a Collector Group with multiple Log Collectors (up to 16)
to ensure log redundancy, increase the log retention period, and
accommodate logging rates that exceed the capacity of a single Log
Collector (see Panorama
Models for capacity information). In any single Collector
Group, all the Log Collectors must run on the same Panorama model:
all M-600 appliances, all M-500 appliances, all, M-200 appliances
all, or all Panorama virtual appliances. For example, if a single
managed firewall generates 48TB of logs, the Collector Group that
receives those logs will require at least six Log Collectors that
are M-200 appliances or two Log Collectors that are M-500 appliances
or Panorama virtual appliances.
A Collector Group with multiple Log Collectors uses the available
storage space as one logical unit and uniformly distributes the
logs across all its Log Collectors. The log distribution is based
on the disk capacity of the Log Collectors (see Panorama
Models) and a hash algorithm that dynamically decides which
Log Collector owns the logs and writes to disk. Although Panorama
uses a preference list to prioritize the list of Log Collectors
to which a managed firewall can forward logs, Panorama does not
necessarily write the logs to the first Log Collector specified
in the preference list. For example, consider the following preference
list:
Managed Firewall | Log Forwarding Preference
List Defined in a Collector Group |
|---|---|
FW1 | L1,L2,L3 |
FW2 | L4,L5,L6 |
Using this list, FW1 will forward logs to L1 so long as that
primary Log Collector is available. However, based on the hash algorithm,
Panorama might choose L2 as the owner that writes the logs to its
disks. If L2 becomes inaccessible or has a chassis failure, FW1
will not know because it can still connect to L1.
In the case where a Collector Group has only one Log Collector
and the Log Collector fails, the firewall stores the logs to its
HDD/SSD (the available storage space varies by firewall model). As soon
as connectivity is restored to the Log Collector, the firewall resumes
forwarding logs where it left off before the failure occurred.
In the case of a Collector Group with multiple Log Collectors,
the firewall does not buffer logs to its local storage if only one
Log Collector is down. In the example scenario where L2 is down,
FW1 continues sending logs to L1, and L1 stores the log data that
would be sent to L2. Once L2 is back up, L1 no longer stores log
data intended for L2 and distribution resumes as expected. If one
of the Log Collectors in a Collector Group goes down, the logs that
would be written to the down Log Collector are redistributed to
the next Log Collector in the preference list.
Palo Alto Networks recommends adding
at least three Log Collectors to a Collector Group to avoid split
brain and log ingestion issues should one Log Collector go down.
See the changes to default Collector
Group behavior for more information.
Two Log Collectors
in a Collector Group is supported but the Collector Group becomes
non-operational if one Log Collector goes down.
Palo Alto Networks recommends the following mitigations if using
multiple Log Collectors in a Collector Group:
- Enable log redundancy when you Configure a Collector Group. This ensures that no logs are lost if any one Log Collector in the Collector Group becomes unavailable. Each log will have two copies and each copy will reside on a different Log Collector. Log redundancy is available only if each Log Collector has the same number of logging disks.Because enabling redundancy creates more logs, this configuration requires more storage capacity. When a Collector Group runs out of space, it deletes older logs.Enabling redundancy doubles the log processing traffic in a Collector Group, which reduces its maximum logging rate by half, as each Log Collector must distribute a copy of each log it receives.
- Obtain an On-Site-Spare (OSS) to enable prompt replacement if a Log Collector failure occurs.
- In addition to forwarding logs to Panorama, configure forwarding to an external service as backup storage. The external service can be a syslog server, email server, SNMP trap server, or HTTP server.