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Zookeeper >> mail # user >> zookeeper on SSD


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Re: zookeeper on SSD
On Wed, Oct 3, 2012 at 9:12 PM, Jun Rao <[EMAIL PROTECTED]> wrote:
> Patrick,
>
> Thanks for the info. Does each ZK write wait for log being flushed to disk?
>

Yes (it's necessary for the guarantees we provide), although the
servers do batching of writes to improve throughput. This doc gives
some insight: http://zookeeper.apache.org/doc/r3.4.4/zookeeperOver.html#Performance

Patrick
> On Wed, Oct 3, 2012 at 6:13 PM, Patrick Hunt <[EMAIL PROTECTED]> wrote:
>
>> My experience with SSDs and ZK has been discouraging. SSDs have some
>> really terrible corner cases for latency. I've seen them take 40+
>> seconds (that's not a mistake - seconds) for fsync to complete. When
>> this happened (every few hours) all of the sessions would timeout.
>>
>> See this article:
>> http://storagemojo.com/2012/06/07/the-ssd-write-cliff-in-real-life/
>>
>> Patrick
>>
>> On Wed, Oct 3, 2012 at 9:59 AM, Jun Rao <[EMAIL PROTECTED]> wrote:
>> > Hi,
>> >
>> > Will storing the ZK commit log on SSD improve ZK write latency? Does a ZK
>> > write wait until data is flushed to disk?
>> >
>> > Thanks,
>> >
>> > Jun
>>
NEW: Monitor These Apps!
elasticsearch, apache solr, apache hbase, hadoop, redis, casssandra, amazon cloudwatch, mysql, memcached, apache kafka, apache zookeeper, apache storm, ubuntu, centOS, red hat, debian, puppet labs, java, senseiDB