On 01/31/2012 09:54 PM, Bob Friesenhahn wrote:
> On Tue, 31 Jan 2012, Thomas Nau wrote:
>> Dear all
>> We have two JBODs with 20 or 21 drives available per JBOD hooked up
>> to a server. We are considering the following setups:
>> RAIDZ2 made of 4 drives
>> RAIDZ2 made of 6 drives
>> The first option "wastes" more disk space but can survive a JBOD failure
>> whereas the second is more space effective but the system goes down when
>> a JBOD goes down. Each of the JBOD comes with dual controllers, redundant
>> fans and power supplies so do I need to be paranoid and use option #1?
>> Of course it also gives us more IOPs but high end logging devices should take
>> care of that
> I think that the answer depends on the impact to your business if data is 
> temporarily not available.  If your business can not
> survive data being temporarily not available (for hours or even a week) then 
> the more conserative approach may be warranted.

We are talking about home directories at a university so some
downtime is ok but fore sure now hours or even days. We do
regular backups plus snapshot send-receive to a remote location.
The main thing I was wondering about is if it's better to have a downtime
if a JBOD fails (rare I assume) or to keep going without any redundancy left.

> If you have a service contract which assures that a service tech will show up 
> quickly with replacement hardware in hand, then
> this may also influence the decision which should be made.

The replacement hardware is kind of on-site as we use it for the
disaster recovery on the remote location

> Another consideration is that since these JBODs connect to a server, the data 
> will also be unavailable when the server is down. 
> The server being down may in fact be a more significant factor than a JBOD 
> being down.

I skipped that, sorry. Of course all JOBDs are connected through multiple
SAS HBAs to two servers so server failure is easy to handle

Thanks for the thoughts

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