… non read ahead requests happening as well, at least 10 times more than number of read-ahead requests. May be it is poor read-ahead performance plus multiple threads doing scattered O_DIRECT (so no OS read-ahead) single page reads… if we allow multiple read-ahead threads. I also can’t wait for Christoffer Hall’s work of Linux AIO support to be…
Post: Recovering Linux software RAID, RAID5 Array
August 27, 2011 By 2 Comments
… login via SSH it can be recovered as any generic Linux server. When you restart the system RAID5 volume which has… Write Access read/write LV Status NOT available LV Size 13.61 TB Current LE 223041 Segments 1 Allocation inherit Read ahead sectors… there are spare sectors available. It might be able to read data from the original sectors or it might fail to…
Post: Heikki Tuuri Innodb answers - Part I
October 26, 2007 By 17 Comments
…. Q10: When Innodb decides to schedule sequential read-ahead, random read ahead ? HT: InnoDB schedules a sequential read-ahead when it notices an ascending access pattern… global MySQL Server option, though it may have problems on Linux if you lock very large portion of physical memory. There…
Post: Heikki Tuuri answers to Innodb questions, Part II
November 4, 2007 By 13 Comments
…: You also say on Unix/Linux only one read-ahead can happen at the same time. How many read-aheads can be waiting in Queue when or Innodb will schedule more read-aheads only when given read-ahead is completed? HT…
Post: The performance effects of new patches
September 9, 2008 By 14 Comments
… to control the number of the IO threads on Unix/Linux and makes the threads to be used equally for parallel… added. innodb_read_ahead (default 3) This controls [enable/disable] of read-ahead. 3: normal 2: enable linear read-ahead only 1: enable random read-ahead only 0… may help the performance. * This test uses “innodb_read_ahead = 0″ (The both of read-ahead are disabled) “innodb_ibuf_contract_const = 50000″ “innodb…
Comment: Choosing innodb_buffer_pool_size
November 17, 2007 By 38 Comments
…: You also say on Unix/Linux only one read-ahead can happen at the same time. How many read-aheads can be waiting in Queue when or Innodb will schedule more read-aheads only when given read-ahead is completed? HT…
Post: SHOW INNODB STATUS walk through
July 17, 2006 By 40 Comments
… flushes, read-ahead and flushing of dirty buffers. Normal reads originated from query executions are executed by threads running queries. On Unix/Linux you… index scan read-ahead may be performed which can increase average read size significantly. So you can think about this value as read-ahead efficiency…
Post: Setting up XFS on Hardware RAID -- the simple edition
December 16, 2011 By 9 Comments
… size BBU enabled with Write-back cache only No read cache or read-ahead No drive write cache enabled Partitioning You want to… boundary. /dev/sda2 * 7813120 27344895 9765888 83 Linux /dev/sda3 27344896 856422399 414538752 83 Linux Several months ago my colleague Aurimas posted… emphasize the point, go read those if you need the theory here. Is it common on modern Linux systems for this to…
Post: Operation Systems do not provide good IO interface for Database Servers
May 11, 2006 By 2 Comments
… there was IO scheduler with these functions in works for Linux Kernel but I have not seen anything production ready. So… not solve anything down. It also could be used for read-ahead requests, which are often speculative and we want them to… “Badger” projects at DIKU We tested some protototype patches for Linux kernel and MySQL but we did not get anything ready…
Post: Aligning IO on a hard disk RAID – the Benchmarks
June 9, 2011 By 11 Comments
…removed some irrelevant information): # Aspersa System Summary Report ############################## Platform | Linux Release | Ubuntu 10.04.2 LTS (lucid) Kernel | …idea File IO benchmark results Sequential read results are expectedly the least interesting. Read-ahead kicked in immediately giving ~9’…
