Block size does not matter on Linux . 256KB on read prefetch (read ahead). Best regards, Vladimir Rodionov Principal Platform Engineer Carrier IQ, www.carrieriq.com e-mail: [email protected]
________________________________________ From: lars hofhansl [[email protected]] Sent: Saturday, February 01, 2014 10:33 PM To: [email protected] Subject: Re: Slow Get Performance (or how many disk I/O does it take for one non-cached read?) Hmm... Interesting. I expected there to be a better improvement from smaller blocks. So it's really just IOPS (and block size does not matter), in which case, yes, HBase checksum will save you 50% IOPS for each data block (and since index blocks are cache) it'll save 50% total IOPS. ________________________________ From: Jan Schellenberger <[email protected]> To: [email protected] Sent: Saturday, February 1, 2014 9:38 PM Subject: Re: Slow Get Performance (or how many disk I/O does it take for one non-cached read?) I've experimented with the block size. Here are results: 4k - 60reads/sec - 1.2GB totalStaticIndexSize 8k - 80reads/sec - 660MB totalStaticIndexSize 16k - 90reads/sec - 330MB totalStaticIndexSize and previously 64k - 80reads/sec - ~100mb totalStaticIndexSize Also, I turned off caching and you are correct, the index blocks seem to be cached always - the blockCachedSize grows until it reaches totalStaticIndexSize and then stops growing. If you turn caching on, it will grow until the maxHeap * blockCacheSize (.4 in my case). I saw no performance difference between caching off/on so I guess off is fine. Yes, I always do a major_compact before testing. I think this probably concludes my question - I will try to upgrade to a newer hbase version to get the CRC32/HDFS check fix and we will probably have to evaluate SSD's. Cheers, everyone. -- View this message in context: http://apache-hbase.679495.n3.nabble.com/Slow-Get-Performance-or-how-many-disk-I-O-does-it-take-for-one-non-cached-read-tp4055545p4055582.html Sent from the HBase User mailing list archive at Nabble.com. Confidentiality Notice: The information contained in this message, including any attachments hereto, may be confidential and is intended to be read only by the individual or entity to whom this message is addressed. If the reader of this message is not the intended recipient or an agent or designee of the intended recipient, please note that any review, use, disclosure or distribution of this message or its attachments, in any form, is strictly prohibited. If you have received this message in error, please immediately notify the sender and/or [email protected] and delete or destroy any copy of this message and its attachments.
