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Created attachment 571210[details]
Screenshot of RHEL 6 chapter 24 remove_on_dev_loss statement
Description of problem:
RHEL 6 online storage administration guide's section on remove_on_dev_loss is incorrect. Chapter 24 on modifying link loss behavior seems to be incorrect. The documentation says that the remove_on_dev_loss is not recommended and is disabled by default, but it is in fact enabled by default.
Here's the proof that it is enabled:
According to a comment within the scsi_transport_fc kernel module, the dev_loss_tmo value now determines the device removal.
[root@cos-qa-tc06s08 scsi]# strings scsi_transport_fc.ko | grep remove
parm=dev_loss_tmo:Maximum number of seconds that the FC transport should insulate the loss of a remote port. Once this value is exceeded, the scsi target is removed. Value should be between 1 and SCSI_DEVICE_BLOCK_MAX_TIMEOUT if fast_io_fail_tmo is not set.
fc_remove_host
scsi_remove_target
sysfs_remove_link
transport_remove_device
I have a screenshot of the document in question that I should be able to attach to this bug.
Version-Release number of selected component (if applicable):
How reproducible:
Steps to Reproduce:
1.
2.
3.
Actual results:
Expected results:
Additional info:
Hi Dale
Can you please indicate exactly what part says that it is disabled by default? I had a look at the section in the screenshot provided but could find nothing there to suggest that remove_on_dev_loss was disabled by default.
So, the default behavior within the code is to remove a device on dev_loss.
The issue with the documentation is that it makes it seem like this is NOT the desirable nor recommended behavior. Please see the warning section in the screenshot that states the use of remove_on_dev_loss is not recommended.
The documentation conflicts with the actual behavior of the RHEL 6.2 OS.
In simple terms:
1. The OS does use remove_on_dev_loss without having to change anything. We can demonstrate this by pulling a cable on the target side of the fabric and waiting until the dev_loss_tmo timer has expired. At that time, the device(s) in question will be removed.
2. The documentation says using remove_on_dev_loss is not recommended.
What I'm asking for is that the documentation be changed to reflect the actual behavior of the OS.
I hope this helps.
Thanks,
Dale
(In reply to comment #3)
> Can you please indicate exactly what part says that it is disabled by
> default? I had a look at the section in the screenshot provided but could
> find nothing there to suggest that remove_on_dev_loss was disabled by
> default.
The docs don't explicitly say "disabled", but seem to indicate this behaviour is not the default and you can optionally choose it:
https://access.redhat.com/knowledge/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Storage_Administration_Guide/modifying-link-loss-behavior.html
In RHEL 6, this module parameter isn't present (confirm with a "modinfo scsi_transport_fc" on RHEL 5 vs. 6) and this device removal behaviour is now the default as far as I can tell. The huge warning therefore doesn't make sense given that this is on and the parameter is no longer available.
(not clearing NEEDINFO, I can't speak authoritatively on this)
Created attachment 571210 [details] Screenshot of RHEL 6 chapter 24 remove_on_dev_loss statement Description of problem: RHEL 6 online storage administration guide's section on remove_on_dev_loss is incorrect. Chapter 24 on modifying link loss behavior seems to be incorrect. The documentation says that the remove_on_dev_loss is not recommended and is disabled by default, but it is in fact enabled by default. Here's the proof that it is enabled: According to a comment within the scsi_transport_fc kernel module, the dev_loss_tmo value now determines the device removal. [root@cos-qa-tc06s08 scsi]# strings scsi_transport_fc.ko | grep remove parm=dev_loss_tmo:Maximum number of seconds that the FC transport should insulate the loss of a remote port. Once this value is exceeded, the scsi target is removed. Value should be between 1 and SCSI_DEVICE_BLOCK_MAX_TIMEOUT if fast_io_fail_tmo is not set. fc_remove_host scsi_remove_target sysfs_remove_link transport_remove_device I have a screenshot of the document in question that I should be able to attach to this bug. Version-Release number of selected component (if applicable): How reproducible: Steps to Reproduce: 1. 2. 3. Actual results: Expected results: Additional info: