[OpenIndiana-discuss] Need thoughts on OpenIndiana+ZFS for backup server

[Gary Gendel]

I tend to agree with Matt.

I've had several catastrophic power incidence on my server running 
OpenSolaris without incident (such as a UPS gone haywire).  Since ZFS 
does transaction-safe reads and writes, the consistency on the disk has 
an extremely low probability of getting corrupt. But there are always 
two things to consider...  Powering off the server this way could cause 
the disks themselves to write garbage and ZFS (or any other filesystem) 
won't have the opportunity to fix it.  Also, there may be pending things 
in the ZFS cache which won't be written.  You can disable the ZFS cache, 
but that will impact performance.

If it's a situation where you don't have control over the servers 
(someone turns off the master switch), then I truly suggest that you put 
a UPS on the server and have a daemon (nut, apsupcd, etc.) that get's 
the signal that the power has been killed and shuts down the servers 
gracefully.

Based upon the goals of Hammer, it looks like ZFS covers them all.  It 
looks like, on Hammer, you have to run a a prune/reblock on the 
filesystem nightly to conserve resources.  I would assume that heavily 
pounding during the day will limit the effective utilization greatly.  
How much overhead do you need for the prune/reblock, 10%, 20%?  What 
happens if there isn't enough room to run it?

You're skirting on very thin ice if you pull the plug to shut down the 
servers no matter what system you use.  Interestingly, there are no 
specs for Hammer in the FS comparison chart.  This doesn't sound like a 
seasoned production filesystem which would scare me even more.

On 2/5/11 6:35 AM, Matt Wilby wrote:
> On 05/02/2011 11:28, Basil Kurian wrote:
>    
>> Here we are running backup servers only during business hours (web
>> development firm). At the end of day , Sometimes the servers are powered
>> off  , without issuing any commands to shutdown them cleanly.
>>
>> On 5 February 2011 16:45, Matt Wilby<matthewwilby at btinternet.com>  wrote:
>>
>>      
>>> On 05/02/2011 10:53, Basil Kurian wrote:
>>>        
>>>> Hi all
>>>>
>>>>
>>>> Currently in our company we are having a Dragonfly BSD backup server with
>>>> Hammer filesystem in it. One senior system administrator in our compay
>>>>          
>>> chose
>>>        
>>>> Hammer filesystem some times back, because Hammer filesystem can easily
>>>> recover in times of power failures. I 'm compelling him to move to ZFS
>>>>          
>>> (on
>>>        
>>>> FreeBSD or OpenIndiana). How durable is data on an ZFS pool (RAID or
>>>>          
>>> mirror)
>>>        
>>>> when  power failure happen frequently.
>>>>
>>>>          
>>> Hi,
>>>
>>> I use ZFS on my backup servers. I can't say we've ever had power
>>> failures because they're in a datacenter, but I would invest in a decent
>>> UPS if it's a regular occurrence. Hard drives don't generally like
>>> having power suddenly removed.....
>>>
>>> ZFS on OpenIndiana will give you nice features like file system
>>> compression, dedupe, snapshots and constant checksumming of of in-use
>>> blocks.
>>>
>>> I've never used Hammer before, but HammerFS doesn't appear to offer
>>> compression yet.
>>>
>>> Just my opinion, but I'd say ZFS is more widely used than Hammer.
>>>
>>> Matt
>>>
>>>
>>>
>>> _______________________________________________
>>> OpenIndiana-discuss mailing list
>>> OpenIndiana-discuss at openindiana.org
>>> http://openindiana.org/mailman/listinfo/openindiana-discuss
>>>
>>>        
>>
>>      
> I don't understand why you would ever want to shut a server down in this
> way.
>
> Can't you just setup a cron to shut them down at a certain time?
>
>
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