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What do BYP (disk bypass) codes mean?

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Applies to

Data ONTAP 7 and earlier

Answer

What are Drive Bypass Events?

fcal link_stats report BYP status.

Example:

localhost> fcstat device_map

Loop Map for channel 4a:

Translated Map: Port Count 28

7 29 27 26 25 24 23 22 21 20 19 18 17 16 45 44

43 42 41 40 39 38 37 36 35 34 33 32

Shelf mapping:

Shelf 1: 29BYP 27 26 25 24 23 22 21 20 19 18 17 16

Shelf 2: 45 44 43 42 41 40 39 38 37 36 35 34 33 32

This means that the disk id 28 has been bypassed.

Drive bypass events are situations that cause the ESH to bypass a drive port thus making it inaccessible by the host and isolating the drive from the loop. There are primarily two different kinds of drive Bypass Events:

  • Threshold Bypasses - Situations where the ESH detects that a certain kind of error is occurring for a specific period of time and the determination is made to bypass the port because of accumulated errors over time or over the amount of data flowing through the loop.
  • Policy Bypasses - Situations where the ESH detects a critical problem and bypasses a drive in order to maintain the integrity of the loop. This might be a "situational" problem which later clears, but once a drive is bypassed, it will remain bypassed until manually cleared by removing and reseating the drive, or by power cycling of the shelf.
  • Self Bypasses - The hard drive electronics determine that the internal circuitry cannot function properly anymore. Thus the drive itself calls to be removed from the loop.

Note: ESH port may also show a bypass. It usually means that the loop has an issue, cable, or SFP. It could also be a speed mismatch that would bypass the ESH port.

Refer to the following document for more information on disk bypass codes: Monitoring the LRC, ESH, ESH2, or ESH4 modules.

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