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HDFS >> mail # user >> Re: Is it safe enough to write edit log in buffer before writing to disk ?


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Re: Is it safe enough to write edit log in buffer before writing to disk ?
Thanks, Todd. I saw the flush code.

On Fri, Jun 11, 2010 at 9:31 AM, Todd Lipcon <[EMAIL PROTECTED]> wrote:
> Hi Jeff,
> All of the FSNamesystem methods call logSync() before returning to the
> client. So, if the edit is lost, it also will not have returned a success to
> the client.
> -Todd
>
> On Thu, Jun 10, 2010 at 6:29 PM, Jeff Zhang <[EMAIL PROTECTED]> wrote:
>>
>> Hi all,
>>
>> I check the source code of EditLogFileOutputStream, it seems hadoop
>> will first write edit log to buffer, then flush to disk. I know that
>> it will improve performance, but in the other hand it will cause the
>> edit log in buffer lost when the name node is down. So I wonder is it
>> possible and necessary to let users do configuration in the conf file
>> to decide whether use buffer or not? Thanks.
>>
>>
>>
>> --
>> Best Regards
>>
>> Jeff Zhang
>
>
>
> --
> Todd Lipcon
> Software Engineer, Cloudera
>

--
Best Regards

Jeff Zhang