[ENBD] Cleanly rebooting/halting an ENBD machine (RAID, LVM, cryptoloop, etcetera)

[Bas van Schaik]

Peter T. Breuer wrote:

>"Also sprach Bas van Schaik:"
>  
>
>>I'm just wondering if you guys have consistency problems when rebooting
>>or halting an ENBD client. Currently, my configuration is as following:
>>
>>enbd devices > RAID5 > LVM > cryptoloop > reiserfs
>>
>>When halting or rebooting, services are stopped in default (Debian?) order:
>>1) enbd
>>2) LVM
>>3) RAID
>>
>>So, enbd is stopped before RAID has had a chance to stop the array
>>cleanly. Correct me if I'm wrong, but I think this can cause consistency
>>    
>>
>
>(...)
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>  
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>>problems when the device is under high load, resulting in an out-of-sync
>>RAID-array. Do you guys have any ideas on this?
>>    
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>If you are running in the layered way you state, you need to 
>
>   1) umount reiserfs (all fs's)
>   2) stop cryptoloop (that device)
>   3) stop lvm        (that device)
>   4) stop raid       (that device)
>   5) stop enbd.
>
>Note that it's perfectly possible to be running raid over lvm (hic), so
>you can't rely on this order as a general solution to all possible
>ills.
>  
>
Sure, this is just my layered configuration. However, it might be a
problem if the reiserfs is in use. What to do in such case? I don't
think a "lazy" unmount provides a working solution, the most important
part is the state of RAID. And of course it's impossible to switch to
"readonly" RAID when the device is in use... Any ideas on this?

Thanks,

Bas