PowerFlex: SDS Devices Missing Data After Reboot in AWS or Azure Cloud Environment
Summary: SDS devices are missing data after reboot.
Symptoms
After a hard OS reboot on one SDS, the SDS devices on that host no longer have data or signatures.
PowerFlex system is running inside a cloud environment, AWS, or Azure.
Symptoms
- SDS node hard reboots (intentional or not)
- Upon coming back up, SDS devices are present but all devices move to an error state upon joining back to the PowerFlex system.
- Devices from the SDS that rebooted are in an error state and cannot be cleared.
- Devices are missing SDS device signatures (from sds trc log):
2023/02/27 06:42:26.477168 7f669822fdb0:mosAsyncIO_OpenFileEx:00465: Opened file /dev/nvme2n1 (fd 18), maxInflight 8, maxIoSize 1310720, ptr 0x7f66a8003bf0 2023/02/27 06:42:26.477313 7f669822fdb0:phyDevMap_ThreadedReadDevId:00732: ERROR: Read device ID of /dev/nvme2n1 took 10 milli rc=INVALID_DEVICE_HEADER_SIGNATURE
- If CloudLink is running, the devices are seen as "unencrypted" and "data_raw" (from svmd.log)
{"mpoint":"/dev/nvme0n1","status":"unencrypted","label":"","type":"data_raw","size":1788, "drives" : ["/dev/nvme0n1"]},"9486948577258625":
{"mpoint":"/dev/nvme1n1","status":"unencrypted","label":"","type":"data_raw","size":1788, "drives" : ["/dev/nvme1n1"]},"9486948577268625":
{"mpoint":"/dev/nvme2n1","status":"unencrypted","label":"","type":"data_raw","size":1788, "drives" : ["/dev/nvme2n1"]},"9486948577278625":
{"mpoint":"/dev/nvme3n1","status":"unencrypted","label":"","type":"data_raw","size":1788, "drives" : ["/dev/nvme3n1"]},"9486948577288625":
{"mpoint":"/dev/nvme4n1","status":"unencrypted","label":"","type":"data_raw","size":1788, "drives" : ["/dev/nvme4n1"]},"9486948577298625":
{"mpoint":"/dev/nvme5n1","status":"unencrypted","label":"","type":"data_raw","size":1788, "drives" : ["/dev/nvme5n1"]},"9491767425":
Impact
Data degraded and a subsequent rebuild if only one node reboots
If more than one node reboots at or near the same time, data loss is a possibility.
Cause
When running inside a cloud environment such as AWS or Azure, if the devices chosen for the underlying hardware are NVMEs, these are ephemeral and the data go away on hard reboot or when the instance is powered down. From the AWS documentation here:
- NVMe SSD drives are ephemeral storage. When instances are powered down, the NVMe devices are wiped, in accordance with AWS design.
- NVMe SSD drives are for extreme performance. Data does not persist following either a planned or unplanned shutdown. A backup solution is recommended.
Resolution
As mentioned in the documentation, this is working as designed. Make sure to have a backup solution.
Impacted Versions
PowerFlex 3.6.x
PowerFlex 4.x