Reese Knowledgebase

What are Drive Bypass Events (taken from NOW)

View Kristian Reese's profile on LinkedIn


If you like this article, please +1 or Recommend via FB with the provided buttons above:

Article ID: 36
by: Reese K.
Posted: 10 May, 2012
Last updated: 10 May, 2012
Views: 2040

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: 29 BYP 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 which 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.

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

---

qhostingfiler1a> fcstat device_map  
Loop Map for channel 0b:
Translated Map: Port Count 56
                  7  29  28  27  26  25  24  23  22  21  20  19  18  17  16  45
                 44  43  41  42  39  38  37  36  32  35  34  33  40  61  60  59
                 57  55  54  53  52  48  51  50  49  56  77  76  75  73  74  71
                 70  69  68  64  67  66  65  72
Shelf mapping:
                Shelf 1:  29  28  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
                Shelf 3:  61  60  59 BYP  57  56  55  54  53  52  51  50  49  48
                Shelf 4:  77  76  75  74  73  72  71  70  69  68  67  66  65  64

After looking at the status of the ESH module for that disk shelf, we can see that the disk was self-bypassed:

qhostingfiler1a> storage show hub 0b.shelf3      
Shelf name:    0b.shelf3
Channel:       0b
Module:        A
Shelf id:      3
Shelf UID:     50:05:0c:c0:02:12:27:2c
Shelf S/N:     N/A
Term switch:   N/A
Shelf state:   ONLINE
Module state:  OK


                               Loop  Invalid  Invalid  Clock  Insert  Stall  Util    LIP
Disk    Disk     Port            up      CRC     Word  Delta   Count  Count  Percent Count
  Id     Bay    State         Count    Count    Count                                  
----------------------------------------------------------------------------------------
[IN  ]          OK                0        0        0      0       0      0    38     0
[OUT ]          OK                0        0        0      0       0      0    18     0
[  48]     0    OK                0        0        0     24       0      0     0     0
[  49]     1    OK                0        0        0      0       0      0     6     0
[  50]     2    OK                0        0        0     24       0      0     6     0
[  51]     3    OK                0        0        0     24       0      0     0     0
[  52]     4    OK                0        0        0     16       0      0     0     0
[  53]     5    OK                0        0        0     24       0      0     0     0
[  54]     6    OK                0        0        0     24       0      0     6     0
[  55]     7    OK                0        0        0     16       0      0     0     0
[  56]     8    OK                0        0        0     16       0      0     0     0
[  57]     9    OK                0        0        0     24       0      0     0     0
[  58]    10    BYP/SELF          0        0        0     24       0      0     4     0
[  59]    11    OK                0        0        0     16       0      0     0     0
[  60]    12    OK                0        0        0     24       0      0     8     0
[  61]    13    OK                0        0        0     32       0      0     8     0

This article was:   Helpful | Not Helpful
Prev   Next
Eliminate messages from system console     Understanding Fractional Reserve

RSS