63144: Acronis Cyber Infrastructure: "Disk write cache disabled/enabled" alert

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Last update: 17-09-2021

Symptoms

Depending on the version of Acronis Cyber Infrastracture one of the following alerts may be observed in WebCP > Monitoring > Alerts:

1. With ACI version 4.0 and lower:

Disk write cache disabled for disk <disk_name> on node "<node_name>"

2. With ACI version 4.5 and higher:

Disk write cache is enabled for disk <disk_name> on node "<node_name>". Disable it to avoid potential data loss in case of a power outage.

Cause

As most hard disk drives do not have flushing capabilities, write cache must be disabled on them, otherwise a power outage may result in data loss in case of enabled write cache.

The alert is intended to warn about HDD write cache feature and prevent possible issues in case of unexpected power outage on node.

Solution

  • The alert 'Disk write cache disabled' for ACI version 4.0 and below should be ignored as invalid, the internal check have been reworked starting with ACI 4.5 version.
  • In case of the alert 'Disk write cache is enabled' it is required to disable write caching manually for the issued disks in the following way:

1. Fetch the state of the Writeback Cache Enable field for the issued disks on node using sdparm or hdparm utility, e.g.:

[root@node01 ~]# sdparm -g WCE /dev/sdd /dev/sdc
/dev/sdd: WDC WUH721816AL5204 C232
WCE 1 [cha: y, def: 1, sav: 1]
/dev/sdd: WDC WUH721816AL5204 C232
WCE 1 [cha: y, def: 1, sav: 1]

or

[root@node02 ~]# hdparm -W /dev/sda
/dev/sda:
 write-caching =  1 (on)

Here WCE 1 or write-caching =  1 (on) output means that write caching is enabled for the disk devices.

2. Disable write caching for the issued disks and verify Writeback Cache Enable value, e.g.:

[root@node01 ~]# sdparm -c WCE /dev/sdd /dev/sdc -S
/dev/sdd: WDC WUH721816AL5204 C232
/dev/sdd: WDC WUH721816AL5204 C232

[root@node01 ~]# sdparm -g WCE /dev/sdd /dev/sdc
/dev/sdd: WDC WUH721816AL5204 C232
WCE 0 [cha: y, def: 1, sav: 0]
/dev/sdd: WDC WUH721816AL5204 C232
WCE 0 [cha: y, def: 1, sav: 0]

or

[root@node02 ~]# hdparm -W0 /dev/sda
/dev/sda:
 setting drive write-caching to 0 (off)
 write-caching =  0 (off)

[root@node02 ~]# hdparm -W /dev/sda
/dev/sda:
 write-caching =  0 (off)

Note, that the alert may be not cleared out automatically after editing write cache feature for the disk, this aspect is planned to be improved in future ACI versions. The following workaround may be applied on the issued node starting since ACI 4.6.1 in order to re-read disks write caching values by UI services and clear out the related alert:

[root@node01 ~]# systemctl restart vstorage-ui-agent

Additionally, it is required to make sure to have write cache disabled for those HDDs on disk controller level, consult with hardware vendor in case of questions.

Contact Acronis support in case of any additional questions or issues regarding this topic.

More information

ACI Administrator Guide: Protecting data during a power outage

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