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From Boris Yen <yulin...@gmail.com>
Subject Re: Repair taking a long, long time
Date Wed, 20 Jul 2011 14:00:45 GMT
We also got the same problem when using 0.8.0. As far as I know, there are a
few issues relative to 'repair' has been marked as resolved at 0.8.1. Hope
this could really solve our problem.

On Wed, Jul 20, 2011 at 8:47 PM, David Boxenhorn <david@citypath.com> wrote:

> I have this problem too, and I don't understand why.
>
> I can repair my nodes very quickly by looping though all my data (when you
> read your data it does read-repair), but nodetool repair takes forever. I
> understand that nodetool repair builds merkle trees, etc. etc., so it's a
> different algorithm, but why can't nodetool repair be smart enough to choose
> the best algorithm? Also, I don't understand what's special about my data
> that makes nodetool repair so much slower than looping through all my data.
>
>
>
> On Wed, Jul 20, 2011 at 12:18 AM, Maxim Potekhin <potekhin@bnl.gov> wrote:
>
>> Thanks Edward. I'm told by our IT that the switch connecting the nodes is
>> pretty fast.
>> Seriously, in my house I copy complete DVD images from my bedroom to
>> the living room downstairs via WiFi, and a dozen of GB does not seem like
>> a
>> problem, on dirt cheap hardware (Patriot Box Office).
>>
>> I also have just _one_ column major family but caveat emptor -- 8 indexes
>> attached to
>> it (and there will be more). There is one accounting CF which is small,
>> can't possibly
>> make a difference.
>>
>> By contrast, compaction (as in nodetool) performs quite well on this
>> cluster. I start suspecting some
>> sort of malfunction.
>>
>> Looked at the system log during the "repair", there is some compaction
>> agent doing
>> work that I'm not sure makes sense (and I didn't call for it). Disk
>> utilization all of a sudden goes up to 40%
>> per Ganglia, and stays there, this is pretty silly considering the cluster
>> is IDLE and we have SSDs. No external writes,
>> no reads. There are occasional GC stoppages, but these I can live with.
>>
>> This repair debacle happens 2nd time in a row. Cr@p. I need to go to
>> production soon
>> and that doesn't look good at all. If I can't manage a system that simple
>> (and/or get help
>> on this list) I may have to cut losses i.e. stay with Oracle.
>>
>> Regards,
>>
>> Maxim
>>
>>
>>
>>
>> On 7/19/2011 12:16 PM, Edward Capriolo wrote:
>>
>>>
>>> Well most SSD's are pretty fast. There is one more to consider. If
>>> Cassandra determines nodes are out of sync it has to transfer data across
>>> the network. If that is the case you have to look at 'nodetool streams' and
>>> determine how much data is being transferred between nodes. There are some
>>> open tickets where with larger tables repair is streaming more then it needs
>>> to. But even if the transfers are only 10% of your 200GB. Transferring 20 GB
>>> is not trivial.
>>>
>>> If you have multiple keyspaces and column families repair one at a time
>>> might make the process more manageable.
>>>
>>
>>
>

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