Why is the LUN in read-only mode when my FSx for ONTAP file system capacity is full?

Short description

If your FSx for ONTAP file system is out of space and your volumes are thin provisioned, then the LUN is read only. Volumes that you create from the Amazon FSx console or the AWS Command Line Interface (AWS CLI) are thin provisioned.

To resolve this issue, increase the space in the file system, volume, and LUN. Then, run an operating system (OS)-level file system check to make sure that the file system is in a healthy state before you use it.

Resolution

Perform diagnostic checks

If your FSx for ONTAP file system at the client OS is read only, then you might see a log entry similar to the following one:

EXT4-fs (dm-11): Remounting filesystem read-only
EXT4-fs (dm-11): previous I/O error to superblock detected
sd 46:0:0:5: [sdan] FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE cmd_age=0s
sd 46:0:0:5: [sdan] Sense Key : Data Protect [current]
sd 46:0:0:5: [sdan] Add. Sense: Space allocation failed write protect
sd 46:0:0:5: [sdan] CDB: Write(10) 2a 00 00 00 00 00 00 00 08 00
blk_update_request: critical space allocation error, dev sdan, sector 0
blk_update_request: critical space allocation error, dev dm-11, sector 0
Buffer I/O error on dev dm-11, logical block 0, lost sync page write

Also, storage space might be limited on the FSx for ONTAP server. To view disk space usage on the server, run the following command:

::> df -h
::> df -h -A

To view space at the LUN level, run the following command. Replace svm_name and lun_path with your values:

::> lun show
::> lun show -vserver svm_name -path lun_path

To determine if the volume is thin provisioned or thick provisioned, run the following commands. Replace svm_name and vol-name with your values:

::> volume show -fields space-slo
::> volume show -vserver svm_name -volume vol_name -fields space-slo

Add capacity to your disk space

To add capacity to your file system, complete the following steps:

1.    Increase the volume capacity.

2.    To increase the size of the LUN, run the following command. Replace vserver_name, volume_name, lun-name, and lun_size with your values:

::> lun resize -vserver vserver_name -volume volume_name -lun lun_name -size lun_size

3.    Run a file system check before you resume use.