ZFS RAIDZ and atacontrol spindown settings

[Arnaud Houdelette]

Mark Stapper wrote:
> Arnaud Houdelette wrote:
>   
>> Mark Stapper a écrit :
>>     
>>> Ivan Voras wrote:
>>>  
>>>       
>>>> 2009/7/21 Mark Stapper <stark at mapper.nl>:
>>>>      
>>>>         
>>>>> Ivan Voras wrote:
>>>>>          
>>>>>           
>>>>>> Mark Stapper wrote:
>>>>>>              
>>>>>>             
>>>>>>> Good day,
>>>>>>>
>>>>>>> I am the proud user of a FreeBSD 7.2 AMD64 system housing,
>>>>>>> amongst other
>>>>>>> things, a data server.
>>>>>>> My "server"(It's called "Yoshi") runs FreeBSD from a mirrored system
>>>>>>> disc, and has a zfs RAIDZ array with 4 discs for bulky data.
>>>>>>> As it is a home server, and I work during the day, these four
>>>>>>> discs were
>>>>>>> spinning happily all day long without much use for them doing so.
>>>>>>> To save the world(and money) I issued the command "atacontrol
>>>>>>> spindown
>>>>>>> 1800" for all the discs in my array spinning them down after thirty
>>>>>>> minutes of idle spinning.
>>>>>>> So far so good, me very happy! However, when I access the array
>>>>>>> after
>>>>>>> the discs have been spun down, it spins up the discs one after the
>>>>>>> other...
>>>>>>> Mind you one AFTER the other, taking 4*9 seconds to do a "ls"
>>>>>>> command on
>>>>>>> my music directory.
>>>>>>> Content as I am with the smooth down- and upspinning of the disks, I
>>>>>>> would like it better if the four discs would spin up simultaneously.
>>>>>>> Thus my  question: "Is it possible to \"group\" discs to be spun up
>>>>>>> together, or to issue a custom command upon upspinning of a disc
>>>>>>> such as
>>>>>>> to spin up other disks?"
>>>>>>>                   
>>>>>>>               
>>>>>> Good question but the answer is probably no - it really only depends
>>>>>> on how ZFS accesses the drives; if it accesses them in sequence, you
>>>>>> can't change it.
>>>>>>               
>>>>>>             
>>>>> I've been looking at writing a shell script which monitors
>>>>> /var/log/messages.
>>>>> something like:
>>>>>
>>>>> If last line in /var/log/messages is like "request while spun down.
>>>>> Starting."
>>>>>    spinup disks
>>>>>
>>>>> couple of problems though, I should probably poll the kernel messages
>>>>> every second or so, but if I only check the last linee, I could
>>>>> miss the
>>>>> spinup message.
>>>>> I could count the number of lines in /var/log/messages and keep
>>>>> count of
>>>>> the number of lines i've seen. Problem with this approach is that it's
>>>>> not very efficient.
>>>>> So I was hoping there is a way to receive this kernel message
>>>>> directly.
>>>>> I am now thinking in the lines of a program which received a signal on
>>>>> new kernel messages available or something similar.
>>>>>
>>>>> Any thoughts?
>>>>>           
>>>>>           
>>>> You could do what "tail -f" does and simply hook a kqueue to get new
>>>> messages from the /var/log/messages file.
>>>>       
>>>>         
>>> I'll try that! thanks!
>>>
>>>   
>>>       
>> As I get quite the same issue with a 4 disk raidz pool, could you
>> please tell me the result of your tries ? which command do you use to
>> force the disks to spin up ?
>>
>> Thanks
>>     
> I have been using a shell script containing:
> #!/bin.sh
> dd if=/dev/ad4 of=/dev/null count=1&
> dd if=/dev/ad6 of=/dev/null count=1&
> dd if=/dev/ad8 of=/dev/null count=1&
> dd if=/dev/ad10 of=/dev/null count=1&
>   

Thanks.

FYI, I made the little script behind to speed up the spinup of the whole 
pool, in case it be some use for anybody :

#!/bin/sh
wait-spinup() {
while true
do
read l
l=`echo $l | grep 'request while spun down'`
  if [ -n "$l" -a "`date +%H%M%S`" != "$d" ]; then
    d=`date +%H%M%S`
    dd if=/dev/ad4 of=/dev/null count=1 2> /dev/null &
    dd if=/dev/ad6 of=/dev/null count=1 2> /dev/null &
    dd if=/dev/ad8 of=/dev/null count=1 2> /dev/null &
    dd if=/dev/ad10 of=/dev/null count=1 2> /dev/null &
  fi
done
}

tail -n 0 -F /var/log/messages | wait-spinup