[mythtv-commits] Ticket #9682: Myth Backend handles loss of NFS mount poorly (was: Myth Backend handles loss of disk poorly)

[MythTV]

#9682: Myth Backend handles loss of NFS mount poorly
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 Reporter:  danielk           |          Owner:  danielk
     Type:  Developer Task    |         Status:  new
 Priority:  minor             |      Milestone:  unknown
Component:  MythTV - General  |        Version:  Trunk Head
 Severity:  medium            |     Resolution:
 Keywords:                    |  Ticket locked:  0
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Old description:

> When an NFS server goes down in the middle of a recording any of the
> backend's ThreadedFileWriters writing to that disk become permanently
> wedged and CPU usage shoots up to near 100%.
>
> Using aio_write() instead of write() should allow us to better handle
> this condition. We should at minimum not use 100% CPU, and ideally
> continue recording to other disks including with the currently blocked
> recorder.

New description:

 When an NFS server goes down in the middle of a recording any of the
 backend's ThreadedFileWriters writing to that disk become permanently
 wedged and CPU usage shoots up to near 100%.

 Using aio_write() instead of write() should allow us to better handle this
 condition. We should at minimum not use 100% CPU, and ideally continue
 recording to other disks including with the currently blocked recorder.

--

Comment (by beirdo):

 First thing to do... if you are worried about NFS mounts disappearing,
 mount them with options "soft,intr,retrans=6".  The default is
 "hard,nointr,retrans=3".  There is some risk of lost data due to doing
 this, but the NFS connection will no longer indefinitely hang.

 Additional to that, the aio_write() may be a good plan (is this portable,
 and will it have the desired affect on non NFS writes?)

-- 
Ticket URL: <http://code.mythtv.org/trac/ticket/9682#comment:1>
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