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Date:      Thu, 23 May 2013 18:08:59 -0500
From:      Joshua Isom <jrisom@gmail.com>
To:        freebsd-questions@freebsd.org
Subject:   Re: file corruption solution (soft-update or ZFS)
Message-ID:  <519EA18B.8080306@gmail.com>
In-Reply-To: <CAN+S=WDGdL5ZabOGp+rBshjmrd9so5Q=wMc5sfDGuEAZxLe3+g@mail.gmail.com>
References:  <CAN+S=WC0ThjT6ox9YdUsAb6++f=+qfCLuct_tN=jsr3KYTezaw@mail.gmail.com> <alpine.BSF.2.00.1305230554360.98184@wonkity.com> <CAN+S=WDGdL5ZabOGp+rBshjmrd9so5Q=wMc5sfDGuEAZxLe3+g@mail.gmail.com>

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On 5/23/2013 7:14 AM, saeedeh motlagh wrote:
> thanks for your reply.
>
> you know i have a sensitive server and unfortunately it is located some
> where that power outage happens much. so i want guarantee my data and avoid
> data lost and file corruption in my server.

Get a good reliable UPS.  Test it regularly, the batteries do fail. 
Test to make sure that it will work, unplug it and let the computer 
drain the battery to time it.  Consider that the battery will degrade 
over time.  One thing google does is put a 12V battery inside the 
chassis to help with the power backup, you might look into it.

> i do not have any problem in RAM and hardware.
>
> i don't know which approach is more suitable for my server. using
> soft-update or ZFS. please help me to select the best one.

If power failure is an issue, you have no guarantee of data loss 
protection unless you use networked storage to a safe place.  UFS soft 
updates protects against file system corruption in case of power loss, 
no guarantees of individual file consistency.  ZFS guarantees no silent 
failures, it doesn't guarantee protection, only that you'll know about 
it.  There is no filesystem that can guarantee you won't lose data in a 
power failure.  Hard drives are known to lie about what's been 
physically synced to disk out of cache in order to improve speed.  If 
the power goes out at the wrong time, you can lose data.  ZFS can find a 
corrupted file and tell you, everything else won't.  If you have a back 
up of that file, you can restore it.

> thank you so much
>
>
>
> On Thu, May 23, 2013 at 4:28 PM, Warren Block <wblock@wonkity.com> wrote:
>
>> On Thu, 23 May 2013, saeedeh motlagh wrote:
>>
>>   hello every body
>>>
>>> i have a question about fixing file corruption in freebsd.
>>>
>>> now i have freebsd8.2 and some times file corruption happened on it. this
>>> issue has a heavy cost for me and i want to avoid it or fixit it
>>> completely. so my question is:
>>>
>>> is it better to upgrade my freebsd to 9.1 and use soft update or migrate
>>> from UFS to ZFS?
>>>
>>
>> That's a judgement call, which means "it depends".
>>
>>
>>   i heard so much about soft update -that is added in freebsd9.1-  which can
>>> fix file corruption in acceptable way with low cost but i don't know how
>>> much is reliable and efficient.
>>>
>>
>> Several things:
>>
>> Soft updates have been around for quite a while.
>> Soft updates journaling is the new addition.
>> Neither of these address file corruption.  Their purpose is to make sure
>> the filesystem does not get corrupted, but individual files could still
>> contain bad data.
>>
>>
>>   in the other hand, i think migration from UFS to ZFS can be another
>>> solution. as i read ZFS is is created to solve all the problems related
>>> integrity file system. is it reliable enough in comparison soft-update?
>>>
>>> now, i want to know which solution is better and why?
>>>
>>
>> Again, it depends.  Does the target system have enough RAM for ZFS?  If
>> the file corruption is due to a hardware problem or an application writing
>> bad data, no filesystem can prevent that.
>>
>
>
>




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