…table2. Of course this could mean a lot of random lookups in case the dataset does not fit …Scan disabled, and the only difference in query time is 48.78s vs 48.91s, so I don’t …to become sequential. The two other most important numbers are values for Innodb_buffer_pool_reads and Innodb_data_read. We…
Post: FusionIO - time for benchmarks
December 8, 2009 By 10 Comments
…times RAID vs SSD vs FusionIO and Testing FusionIO: strict_sync…Random reads: From this graph we see that fully utilize FusionIO card we need 4 or more working threads. Random…Sequential reads: With sequential reads the same story with 4 threads. Sequential writes: This is what I mention on sequential…
Post: Aligning IO on a hard disk RAID – the Benchmarks
June 9, 2011 By 11 Comments
… the difference between sequential writes with WT cache and WB cache: Random read. This is …random reads. Regardless of the file size, the difference between aligned and misaligned reads was the same and, WT -vs… similar, due to high concurrency response time in the first case is significantly better…
Post: Heikki Tuuri Innodb answers - Part I
October 26, 2007 By 17 Comments
…When Innodb decides to schedule sequential read-ahead, random read ahead ? HT: InnoDB schedules a sequential read-ahead when it …- how many random and sequential read aheads can be happening at the same time HT: All read-aheads … and it would write at 100MBps vs 33MBps. Any plans to enable tuning …
Post: How multiple disks can benefit for single client workload ?
April 26, 2008 By 4 Comments
… is completed. Innodb tries to optimize these reads a bit – there is sequential read ahead and random read ahead which are designed to spot data… in both cases we have 2.2 vs 5.5ms which is 2.5 times difference – This is a lot, but remember…. If you ask most people what would be faster for random reads (writes are obvious) – RAID0 or RAID1 most will think they…
Comment: Disaster: LVM Performance in Snapshot Mode
February 6, 2009 By 55 Comments
…sequential output block)!!! iozone gives even more statistics. It lists the numbers for Write,Read,Random Write,Random Read,Re-write,Re-read. Let’s just pick up Random Write and Random Read because of their importance: RAID 10 with LVM vs…
Post: EC2/EBS single and RAID volumes IO benchmark
August 6, 2009 By 13 Comments
…=$size –file-test-mode=$mode\ –max-time=60 –max-requests=10000000 –num-threads=$… tested modes: seqrd (sequential read), seqwr (sequential write), rndrd (random read), rndwr (random write), rndrw (random read-write). And sysbench… worse than RAID10. But speaking RAID0 vs RAID10 it’s your call. For…
Post: MySQL 6.0 vs 5.1 in TPC-H queries
March 25, 2008 By 17 Comments
… also, but I guess it is Multi-Range-Read feature which allows to read data not row-by-row but in batches… system we have on this server. This is because of Random I/O we had during execution of query, as MySQL… have sequential I/O with 65362 rkB/s (compare 1200 rkB/s with random I/O), that allows to execute query ~40 times…
Post: Why MySQL could be slow with large tables ?
June 9, 2006 By 139 Comments
…1% of the table. The times for full table scan vs range scan by index: mysql…random places – this may affect index scan/range scan speed dramatically. The rows referenced by indexes also could be located sequentially… be completely random. We’ll need to perform 30 millions of random row reads, which …
Post: InnoDB: look after fragmentation
November 5, 2009 By 12 Comments
…` int(10) unsigned default NULL, PRIMARY KEY (`tracker_id`,`username`,`time_id`), KEY `block_id` (`block_id`) ) ENGINE=InnoDB Table has… extended stats: # Query_time: 17.765369 Lock_time: 0.000137 Rows_sent: 1 Rows_examined: 11569733 Rows_affected: 0 Rows_read: 11569733 # InnoDB…
