NVRAM problems

Types of NVRAM problems

This section describes two types of NVRAM problems:

• NVRAM battery failure
• Inconsistent NVRAM contents

What F220, F330, and F540 filers do when NVRAM battery is low

This section applies only to the NetApp F220, NetApp F330, and NetApp F540 filers.

If the filer detects low batteries on the NVRAM card, it gives advance warning and automatically shuts down every 24 hours. You can change the time interval with the raid.timeout option to the options command.

If the filer is in degraded mode and the NVRAM batteries are low, it fails to boot. Replace the NVRAM batteries immediately.

Very rarely do NVRAM battery failures cause data loss. When the filer executes the halt command, it flushes the contents of NVRAM to disk and turns off the NVRAM so that no battery power is used.

How the filer handles inconsistent NVRAM contents

The filer performs a number of checks to ensure that the NVRAM contents are consistent. If the contents are inconsistent, the filer performs one of following actions:

Inconsistency due to improperly updated volume

If the inconsistency is due to a failure to update a volume properly, the filer displays a message suggesting that you halt the filer with the halt command, take the offending volume off-line in Maintenance mode, and reboot the filer.

Inconsistency due to log updates for off-line volume

If the inconsistency is due to the log having updates for an off-line volume, the filer asks whether to discard them.

Inconsistency due to other reasons

If there are many inconsistencies that cannot be repaired, the filer discards the inconsistent contents and creates a core dump file. The file requests received during the last few seconds before the filer shuts down are lost. This does not cause the file system to become inconsistent, but files written during the last 10 seconds before shutdown might contain old or incorrect data. Also, because the parity of some recently written stripes might be incorrect, the filer must do a parity check on the entire RAID array. The parity check, and any correction, is performed on-line; that is, the filer conducts the test in the background while continuing otherwise normal operation.

This kind of data error can happen only when you boot a system after a failure or after you turn off a filer without using the halt command.

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Part No. 210-02334
File: trbl4.htm
Last updated: 04/26/99 08:11:58