Re: NVRAM support

[Mirko Benz <mirko.benz@web.de>]

Hi,

My intention was not to use a NVRAM device for swap.

Enterprise storage systems use NVRAM for better data protection/faster 
recovery in case of a crash.
Modern CPUs can do RAID calculation very fast. But Linux RAID is 
vulnerable when a crash during a write operation occurs.
E.g. Data and parity write requests are issued in parallel but only one 
finishes. This will
lead to inconsistent data. It will be undetected and can not be 
repaired. Right?

How can journaling be implemented within linux-raid?

I have seen a paper that tries this in cooperation with a file system:
„Journal-guided Resynchronization for Software RAID“
www.cs.wisc.edu/adsl/Publications

But I would rather see a solution within md so that other file systems 
or LVM can be used on top of md.

Regards,
Mirko

Erik Mouw schrieb:
> On Fri, Feb 10, 2006 at 05:02:02PM -0800, dean gaudet wrote:
>   
>> On Fri, 10 Feb 2006, Bill Davidsen wrote:
>>     
>>> Erik Mouw wrote:
>>>       
>>>> You could use it for an external journal, or you could use it as a swap
>>>> device.
>>>>  
>>>>         
>>> Let me concur, I used external journal on SSD a decade ago with jfs (AIX). If
>>> you do a lot of operations which generate journal entries, file create,
>>> delete, etc, then it will double your performance in some cases. Otherwise it
>>> really doesn't help much, use as a swap device might be more helpful depending
>>> on your config.
>>>       
>> it doesn't seem to make any sense at all to use a non-volatile external 
>> memory for swap... swap has no purpose past a power outage.
>>     
>
> No, but it is a very fast swap device. Much faster than a hard drive.
>
>
> Erik
>
>   

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