It's not IO intense, it's IO latency sensitive eg. if other processes are sucking up most of the IO bandwidth then ZK will have a hard time taking quorum decisions.
Disks are cheap, and a single 7.2k dedicated disk can be enough. J-D On Thu, Jul 8, 2010 at 5:38 PM, Arun Ramakrishnan <aramakrish...@languageweaver.com> wrote: > Good to know ZK is IO intense. > Since ZK does not require much disk space and is IO intense. Has anyone > played with using solid state drives for ZK. > We have a 20 node cluster. It would be feasible to have a 3 node ZK all > configured with solid state drives. > > Thanks > Arun > > -----Original Message----- > From: Jonathan Gray [mailto:jg...@facebook.com] > Sent: Thursday, July 08, 2010 4:25 PM > To: user@hbase.apache.org > Subject: RE: zookeeper & HBase > > ZK is sensitive to IO starvation which is why it is recommended to keep it on > a separate node or separate disk. In most cases, giving ZK its own disk is > sufficient and dedicated node(s) are unnecessary. > > On smallish clusters like 10 nodes, I would recommend starting with just 1 ZK > node co-located with your NameNode and HMaster, but with a dedicated disk > just for ZK. Since the NN is a SPOF, having one ZK doesn't really lower your > fault tolerance, except that it may be on a non-raided disk. I encourage > RAID usage for NN and ZK. JBOD for DN/RS. > > JG > >> -----Original Message----- >> From: vramanatha...@aol.com [mailto:vramanatha...@aol.com] >> Sent: Thursday, July 08, 2010 4:20 PM >> To: user@hbase.apache.org >> Subject: zookeeper & HBase >> >> >> I'm trying to have our deployment layout..I read one of the >> articles/FAQ (probably JG's)...that it's better to >> have zookeeper on separate cluster/separate sets of machine..I'm >> assuming that is the right approach.. >> >> >> All our transactions are HBase (inserts, mapreduce-table as input, >> another table as output, other queries,..) >> Based on other thread on locality..RegionServer & Datanode i'll put on >> same hosts.. >> >> If these boxes have enough capacity, do we need to put zookeeper on >> separate cluster? >> If it is on a separate cluster, my understanding is zookeper has much >> smaller memory footprint compared >> to HRegionServer/Datanodes..& it shld need that much CPU as >> well..correct? >> >> Is there any suggested guidance on number of zookeeper vs number of >> regionservers?..looking for some ratio..say 10 node cluster.. >> how many zookeeper..? >> >> Please ignore responding to this ..if this is outside the etiquette >> thanks >> venkatesh >> > >
