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From ameet kini <ameetk...@gmail.com>
Subject Re: Table splitting
Date Wed, 12 Dec 2012 18:32:39 GMT
If its moved for balance or recovery purposes, are there any mechanisms to
copy the blocks over to the new location? Would compaction be this
mechanism? Or is it automatically done as part of tablet migration?

On Wed, Dec 12, 2012 at 1:29 PM, Eric Newton <eric.newton@gmail.com> wrote:

> Well, you have to assume the tablet does not get moved for balancing or
> recovery.
>
> -Eric
>
>
> On Wed, Dec 12, 2012 at 1:27 PM, ameet kini <ameetkini@gmail.com> wrote:
>
>>
>> Ok, so in short, assuming that there's sufficient local disk space, a
>> given tablet having all its blocks local relies on HDFS's guarantee that
>> the first replica of a block will be local as long as the tablet server is
>> also a data node. Yes?
>>
>>
>>
>> On Wed, Dec 12, 2012 at 1:18 PM, Eric Newton <eric.newton@gmail.com>wrote:
>>
>>> Check out o.a.a.server.util.LocalityCheck
>>>
>>> -Eric
>>>
>>>
>>> On Wed, Dec 12, 2012 at 1:17 PM, John Vines <vines@apache.org> wrote:
>>>
>>>> When a file gets written to hdfs, there is a guarantee the file is
>>>> local as long as that systems disks are not full. Accumulo does not have
a
>>>> locality guarantee as tablets will migrate on occasion. However, as data
is
>>>> added, major compactions will occur which will restore locality.
>>>>  On Dec 12, 2012 1:09 PM, "ameet kini" <ameetkini@gmail.com> wrote:
>>>>
>>>>>
>>>>> Along these lines....
>>>>>
>>>>> Can someone help me understand how tablets map to files on disk in
>>>>> HDFS? From what I understand, after a compaction, there may be one (or
>>>>> more?) files on HDFS for a given tablet. Each file can consist of multiple
>>>>> HDFS blocks. Does Accumulo guarantee that the tablet serving a given
data
>>>>> range finds all its blocks locally? If so, how does it keep this guarantee?
>>>>> Wouldn't HDFS distribute these blocks around based on HDFS balancing
>>>>> strategy?
>>>>>
>>>>> Thanks,
>>>>> Ameet
>>>>>
>>>>> On Tue, Dec 11, 2012 at 9:37 AM, William Slacum <
>>>>> wilhelm.von.cloud@accumulo.net> wrote:
>>>>>
>>>>>> Tablets will split automatically, down to the granularity of a row.
>>>>>>
>>>>>>
>>>>>> On Tue, Dec 11, 2012 at 9:32 AM, Mathias Herberts <
>>>>>> mathias.herberts@gmail.com> wrote:
>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> I've read the user manual for v1.4.2 and I have not seen any
mention
>>>>>>> of automatic tablet splitting. Is there such a thing in Accumulo
or is
>>>>>>> pre-splitting the only way to split a table?
>>>>>>>
>>>>>>> Thanks,
>>>>>>>
>>>>>>> Mathias.
>>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>
>>
>

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