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Date:      Thu, 21 Jun 2012 16:30:13 +0200
From:      Julien Cigar <jcigar@ulb.ac.be>
To:        freebsd-questions@freebsd.org
Subject:   Re: Is ZFS production ready?
Message-ID:  <4FE32FF5.60603@ulb.ac.be>
In-Reply-To: <CA%2BD9QhvR_eKtVxdKcaMyOS7tLw_AOHKgUy3o7mJn2b=chMA0Xw@mail.gmail.com>
References:  <4FE2CE38.9000100@gmail.com> <CAPj0R5Kmi-%2BdJ7mPvTrTAoS8O983svOyR2WyK2_v1Cr07dSS_A@mail.gmail.com> <alpine.BSF.2.00.1206211413140.2263@wojtek.tensor.gdynia.pl> <CA%2BD9QhuQ%2BbxKW9%2BdX%2BzS9mErwz8JSkV2G7qL0KfB8BH_LGJAgA@mail.gmail.com> <alpine.BSF.2.00.1206211539230.2903@wojtek.tensor.gdynia.pl> <CA%2BD9QhvR_eKtVxdKcaMyOS7tLw_AOHKgUy3o7mJn2b=chMA0Xw@mail.gmail.com>

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One interesting feature of ZFS if it's block checksum: all reads and 
writes include block checksum, so it can easily detect situations where, 
for example, data is quietly corrupted by RAM.
This feature is very important for databases.

On 06/21/2012 15:58, Matthias Gamsjager wrote:
> On Thu, Jun 21, 2012 at 3:43 PM, Wojciech Puchar<
> wojtek@wojtek.tensor.gdynia.pl>  wrote:
>
>> I really want to see your face when you fsck 48TB w/o ffs+j (since that is
>>> so young must be immature :S ) of data with the phone ring non stop with
>>>
>> Even if ZFS would be the only filesystem in existence i would make one per
>> 2 disks (single mirror).
>>
>> No matter what's going on, what do you prefer in case say - double disk
>> failure from one mirror on 48 disk systems?
>>
>> losing completely data of 1/24 of users (and then restoring that amount
>> from backups), or losing randomly chosen 1/24 of files from whole system?
>>
>> answer yourself.
>>
> Sorry but I don;t follow you right there. with 48 disks you would not
> mirror 24vs24. I will perform very well but there is too much risk in that.
> you would rather go with a raidz2 stripe sets.
>
>
>> With UFS of  course i would have single disk fsck time - less than a hour.
>> which CAN be done out of work hours with soft updates.
>>
>> i normally turn off automatic fsck for large data filesystems, and if
>> crash happened i run it after/before work hours.
>>
>>
>> raid is not a backup. You can loose data with any configuration or fs. so
> like in the compiler discussion. There is no perfect something in this
> world. It's always a tradeoff.
> with ZFS you have access to most advanced techniques and I believe that
> data is most safe with raidz3 as it can be. UFS cant match that and you
> have to rely on a raidcontroller which can screw up your data as well.
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