Re: Derby Database Corruption Issues

[Peter Ondruška]

Hi,

This is still valid (and in general for all systems utilising logging).

Regards,
p.

On 12 July 2017 at 20:04, Shreyans Jain  wrote:

> I was reading https://wiki.apache.org/db-derby/DatabaseCorruption and i
> found prevention of corruption which states
> "Switch off the machine's write caching" . now the article is written in
> 2013. Is it still application to derby database corruption or now it has no
> effect.
>
> Regards,
> Shreyans Jain
>



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Peter Ondruška

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Re: Derby Database Corruption Issues

[Shreyans Jain]

Also the same article displays " write cache techniques. Some hardware has
a default setting of 'write cache' set to enabled. This functionality will
interfere with Derby's expectation of what is written when to the disk, and
has shown to cause database corruption. "

Is it the same write cache that we can disable via OS on windows 10 from
Device Manager > Properties of Disk Drive > Policies tab or it has to be
disabled from somewhere in BIOS.

Regards,
Shreyans Jain

On Thu, Jul 13, 2017 at 12:32 AM, Kristian Waagan 
wrote:

> Hi Shreyans,
>
> I believe this is still valid advice, but the details depend on your
> IO-system, your operating system and your server hardware.
>
> The issue here is that Derby is told the data has been written to stable
> storage, but then it has in fact not. If the machine crashes at this point
> data may be lost.
> For instance, if you are using a SAN there is typically a battery / UPS
> backed buffer (or other types of buffers that don't loose data in case of a
> power outage) on the "storage side", but for this to be useful you must
> ensure data is pushed through the IO driver and is not buffered locally by
> the operating system.
>
> Using asynchronous writes is a typical way of obtaining better [write]
> performance. In many cases the downside is a higher chance of data
> corruption.
> This may or may not be acceptable for your application.
>
>
> Regards,
> --
> Kristian
>
> Den ons. 12. jul. 2017, 20:04 skrev Shreyans Jain  >:
>
>> I was reading https://wiki.apache.org/db-derby/DatabaseCorruption and i
>> found prevention of corruption which states
>> "Switch off the machine's write caching" . now the article is written in
>> 2013. Is it still application to derby database corruption or now it has no
>> effect.
>>
>> Regards,
>> Shreyans Jain
>>
>

Re: Derby Database Corruption Issues

[Kristian Waagan]

Hi Shreyans,

I believe this is still valid advice, but the details depend on your
IO-system, your operating system and your server hardware.

The issue here is that Derby is told the data has been written to stable
storage, but then it has in fact not. If the machine crashes at this point
data may be lost.
For instance, if you are using a SAN there is typically a battery / UPS
backed buffer (or other types of buffers that don't loose data in case of a
power outage) on the "storage side", but for this to be useful you must
ensure data is pushed through the IO driver and is not buffered locally by
the operating system.

Using asynchronous writes is a typical way of obtaining better [write]
performance. In many cases the downside is a higher chance of data
corruption.
This may or may not be acceptable for your application.


Regards,
-- 
Kristian

Den ons. 12. jul. 2017, 20:04 skrev Shreyans Jain :

> I was reading https://wiki.apache.org/db-derby/DatabaseCorruption and i
> found prevention of corruption which states
> "Switch off the machine's write caching" . now the article is written in
> 2013. Is it still application to derby database corruption or now it has no
> effect.
>
> Regards,
> Shreyans Jain
>

Re: Derby Database Corruption Issues

[Camilla Haase]

I'm pretty certain that it is still current. See the section 
"Maintaining Database Integrity" in the Derby Server and Administration 
Guide for your release, reachable from 
http://db.apache.org/derby/manuals/index.html.


Kim

On 7/12/2017 2:40 PM, Shreyans Jain wrote:
I was reading Derby Database Corruption Issues on wiki of derby and i 
found prevention of corruption which states "Switch off the machine's 
write caching" . Now the article was last edited 2014-12-13 16:32:01 by 
50. Is it still application to derby database corruption or now it has 
no effect.


Regards,
Shreyans Jain