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From Jay Kreps <jay.kr...@gmail.com>
Subject Re: new log.dirs property (as opposed to log.dir)
Date Wed, 14 Aug 2013 23:16:00 GMT
If you get a disk error that results in an IOException the broker will shut itself down. You
would then have the option of replacing the disk or deleting that data directory from the
list. When the broker is brought back up the intact partitions will quickly catch up and be
online; the destroyed partitions will have to fully rebuild off the other replicas and will
take a little longer but will automatically come back online once they have restored off the


Sent from my iPhone

On Aug 14, 2013, at 1:49 PM, Jason Rosenberg <jbr@squareup.com> wrote:

> I'm getting ready to try out this configuration (use multiple disks, no
> RAID, per broker).  One concern is the procedure for recovering if there is
> a disk failure.
> If a disk fails, will the broker go offline, or will it continue serving
> partitions on its remaining good disks?  And if so, is there a procedure
> for moving the partitions that were on the failed disk, but not necessarily
> all the others on that broker?
> Jason
> On Thu, Jun 20, 2013 at 3:15 PM, Jason Rosenberg <jbr@squareup.com> wrote:
>> yeah, that would work!
>> On Thu, Jun 20, 2013 at 1:20 PM, Jay Kreps <jay.kreps@gmail.com> wrote:
>>> Yeah we didn't go as far as adding weighting or anything like that--I
>>> think we'd be open to a patch that did that as long as it was
>>> optional. In the short term you can obviously add multiple directories
>>> on the same disk to increase its share.
>>> -Jay
>>> On Thu, Jun 20, 2013 at 12:59 PM, Jason Rosenberg <jbr@squareup.com>
>>> wrote:
>>>> This sounds like a great idea, to just disks as "just a bunch of disks"
>>> or
>>>> JBOD.....hdfs works well this way.
>>>> Do all the disks need to be the same size, to use them evenly?  Since it
>>>> will allocate partitions randomly?
>>>> It would be nice if you had 2 disks, with one twice as large as the
>>> other,
>>>> if the larger would be twice as likely to receive partitions as the
>>> smaller
>>>> one, etc.
>>>> I suppose this goes into my earlier question to the list, vis-a-vis
>>>> heterogeneous brokers (e.g. utilize brokers with different sized
>>> storage,
>>>> using some sort of weighting scheme, etc.).
>>>> Jason
>>>> On Thu, Jun 20, 2013 at 11:07 AM, Jay Kreps <jay.kreps@gmail.com>
>>> wrote:
>>>>> The intention is to allow the use of multiple disks without RAID or
>>>>> logical volume management. We have found that there are a lot of
>>>>> downsides to RAID--in particular a huge throughput hit. Since we
>>>>> already have a parallelism model due to partitioning and a fault
>>>>> tolerance model with replication RAID doesn't actually buy much. With
>>>>> this feature you can directly mount multiple disks as their own
>>>>> directory and the server will randomly assign partitions to them.
>>>>> Obviously this will only work well if there are enough high-throughput
>>>>> partitions to make load balance evenly (e.g. if you have only one big
>>>>> partition per server then this isn't going to work).
>>>>> -Jay
>>>>> On Wed, Jun 19, 2013 at 11:01 PM, Jason Rosenberg <jbr@squareup.com>
>>>>> wrote:
>>>>>> is it possible for a partition to have multiple replicas on different
>>>>>> directories on the same broker?  (hopefully no!)
>>>>>> On Wed, Jun 19, 2013 at 10:47 PM, Jun Rao <junrao@gmail.com>
>>>>>>> It takes a comma separated list and partition replicas are randomly
>>>>>>> distributed to the list.
>>>>>>> Thanks,
>>>>>>> Jun
>>>>>>> On Wed, Jun 19, 2013 at 10:25 PM, Jason Rosenberg <jbr@squareup.com
>>>>>>> wrote:
>>>>>>>> In the 0.8 config, log.dir is now log.dirs.  It looks like
>>>>> singular
>>>>>>>> log.dir is still supported, but under the covers the property
>>>>>>> log.dirs.
>>>>>>>> I'm curious, does this take a comma separated list of directories?
>>>>> The
>>>>>>> new
>>>>>>>> config page just says:
>>>>>>>> "The directories in which the log data is kept"
>>>>>>>> Also, how does kafka handle multiple directories?  Does it
>>> each
>>>>>>>> directory as a separate replica partition, or what?
>>>>>>>> Jason

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