[Sheepdog] sheepdog and RAID

Ski Mountain ski_the_mountain at yahoo.com
Mon Mar 21 16:21:48 CET 2011

>At Thu, 17 Mar 2011 13:49:34 -0700 (PDT),
>Ski Mountain wrote:
>> Thanks for the reply.
>> While setting up RAID 0 would be a option, there must be more elegant solutions 
>> out there.  Just because one disk out of the whole array dies breaking the 
>> array and drastically changing the size of the sheepdog cluster.  
>> One problem I do see with starting many sheep daemons on the same server that 

>> has many disks is that (especially on small clusters) it is possible for all 
>> data for one or many Virtual Machine to be stored on one physical server.  
>Could you explain more details about this?  Fixing this looks the
>right way to go to me.

Since as far as I understand the ring architecture, each machine sits on a ring 
and VM's are RAIDed across the ring.  

Having a sheep on a server that has many disks (these days it is very easy to 
have 10+ disks on one server) , and the best way to set up a machine with many 
disks is to assign a sheep daemon to each disk.  I am simply saying it would be 
good if there where some additional sanity checks put into the sheepdog 
architecture so that it is not possible for a VM to be stored entirely on one 
server with many disks.  I know this would be the exception, not the rule, but 
would just like all bases to be covered.

Or is that already listed under the to do as "better data re-balancing"

>> Would it be possible to do say
>> sheep /store_disk0  /store_disk1  /store_disk2  /store_disk3  /store_disk4  
>> /store_disk5 /store_disk6
>> So all mount points on a server would be handled by the same sheep using 
>> multiple threads
>> Add a mount point 
>> sheep -a /store_disk7
>> Remove a mount point
>> sheep -r /store_disk7
>It is possible to support multiple disks.  But if running multiple
>daemons solves the problem, I'd like to keep the current simple design
>(one daemon for one disk).+

Would it be possible to run one sheep daemon per a server, but spawn a child 
process for each disk.  Then use the above method for adding and removing disks 
for the machine so that the administrator does not have to keep track of port 



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