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From <Yulin...@DELL.com>
Subject RE: hbase time skew
Date Mon, 18 Mar 2013 22:06:43 GMT
So, how about the time changes? Actually in our case, we only have one node.   Let's say initially
the customer does not install a NTP server and the clock becomes slow. Then the customer installs
a new NTP server, the clock is adjusted by the NTP server, which ends up being advanced 5
mins.    Would this 'sudden' clock change cause any issues?  We tested on our test bed and
found 5 hours advance of the clock would cause major issues. I'm not sure if it would be the
same behavior if the clock is being advanced 3 ~ 5 mins?

Thanks,

YuLing

-----Original Message-----
From: Michel Segel [mailto:michael_segel@hotmail.com] 
Sent: Monday, March 18, 2013 2:29 PM
To: user@hbase.apache.org
Subject: Re: hbase time skew

The actual time isn't an issue. It's that all of the nodes in the cluster have the same time...
Give or take a couple of ms.



Sent from a remote device. Please excuse any typos...

Mike Segel

On Mar 18, 2013, at 2:39 PM, <Yuling_C@DELL.com> wrote:

> The problem is that in our case, the customer configures the NTP server and it could
be invalid. We're trying to cover user error cases, but on the other hand we're trying to
understand how big time skew hbase can handle...
> 
> Thanks,
> 
> YuLing
> 
> -----Original Message-----
> From: Kevin O'dell [mailto:kevin.odell@cloudera.com]
> Sent: Saturday, March 16, 2013 5:49 AM
> To: user@hbase.apache.org
> Subject: Re: hbase time skew
> 
> I am going to agree with Michael on this one.  Don't change the clock skew, fix it.
> 
> On Fri, Mar 15, 2013 at 9:56 PM, Michel Segel <michael_segel@hotmail.com> wrote:
>> Create an ntp server local to the cluster? This will eliminate the skew in the first
place.
>> 
>> Sent from a remote device. Please excuse any typos...
>> 
>> Mike Segel
>> 
>> On Mar 15, 2013, at 3:53 PM, Ted Yu <yuzhihong@gmail.com> wrote:
>> 
>>> Are you using 0.94.x ?
>>> 
>>> If so, see the following:
>>> 
>>>   maxSkew = c.getLong("hbase.master.maxclockskew", 30000);
>>>   warningSkew = c.getLong("hbase.master.warningclockskew", 10000); 
>>> ./src/main/java/org/apache/hadoop/hbase/master/ServerManager.java
>>> 
>>> Cheers
>>> 
>>> On Fri, Mar 15, 2013 at 3:49 PM, <Yuling_C@dell.com> wrote:
>>> 
>>>> Hi,
>>>> 
>>>> We recently encountered the issue that HBase tables got into a 
>>>> state that was not disabled nor enabled. We found that the root 
>>>> cause was the linux clock skewed more than 5 hours. I googled and 
>>>> understood that hbase can only  handle about a couple of seconds 
>>>> time skew. We were wondering if there's any configuration in HBase 
>>>> that we can do so as to increase the number of seconds that hbase could handle?
>>>> 
>>>> Thanks very much,
>>>> 
>>>> YuLing
> 
> 
> 
> --
> Kevin O'Dell
> Customer Operations Engineer, Cloudera
> 

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