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From Jonathan Ellis <jbel...@gmail.com>
Subject Re: Multiple Data Directories
Date Thu, 25 Feb 2010 21:07:58 GMT
In the "worst" case, compaction combines them all into a single file
anyway.  So I think your approach is flawed.  It's designed to allow
adding capacity by adding nodes, not just by adding more space, or
your cpu / ram ratio will degrade.

On Thu, Feb 25, 2010 at 2:48 PM, Anthony Molinaro
<anthonym@alumni.caltech.edu> wrote:
> Okay, so the disk sizing seems to make sense for what I am seeing, the
> disk which seems to get all the data is the largest.  On the new machines
> which have 3 disks of equal size, compaction seems to be distributing
> among the disks.
>
> Raid0 would sort of defeat the purpose of being able to add additional
> capacity on the fly (ie, adding ebs volumes to increase capacity), as
> I need to know ahead of time what my configuration is.
>
> The new boxes ended up with all the data files in one directory because
> of the bug in 0.5.0 when bootstrapping with multiple directories which
> I worked around by using one directory, bootstrapping, then adding
> the other directories.
>
> So when I have the situation of I just added an additional directory
> with space equal to a current directory, is there any way to redistribute
> the data files?  The operations page makes me think that maybe nodeprobe
> repair might do it, will it?
>
> Thanks,
>
> -Anthony
>
> On Thu, Feb 25, 2010 at 01:43:22PM -0600, Jonathan Ellis wrote:
>> Compaction is why http://wiki.apache.org/cassandra/CassandraHardware
>> recommends raid0-ing if you are concerned about free disk space
>> limits.
>>
>> On Thu, Feb 25, 2010 at 1:36 PM, Gary Dusbabek <gdusbabek@gmail.com> wrote:
>> > Cassandra always compacts to the directory with the most free space.
>> > There is not a way to influence this.
>> >
>> > Gary
>> >
>> > On Thu, Feb 25, 2010 at 13:23, Anthony Molinaro
>> > <anthonym@alumni.caltech.edu> wrote:
>> >> Hi,
>> >>
>> >>  So is there anyway to force distribution among DataFileDirectory entries
>> >> when you add a new one?  Looking at the nodeprobe operations it seems like
>> >> repair which causes a major compaction might do it?  I've tried shutting
a
>> >> node down moving files around by hand and starting up, but the next
>> >> compaction seems to move everything back to a single directory?
>> >>
>> >>  I do see files show up in other directories as they are flushed, but
>> >> then they all seem to make their way back to the first directory in the
>> >> list.
>> >>
>> >> Thanks,
>> >>
>> >> -Anthony
>> >>
>> >> --
>> >> ------------------------------------------------------------------------
>> >> Anthony Molinaro                           <anthonym@alumni.caltech.edu>
>> >>
>> >
>
> --
> ------------------------------------------------------------------------
> Anthony Molinaro                           <anthonym@alumni.caltech.edu>
>

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