… lets comment on IO vs Disk question. If you look at Disk Based databases all data accesses are treated as IOs – it can be… the people understand IO and as not as I typically use these terms. For me IO is IO bound workload – disks are moving and… – single client work load does not necessary means single outstanding disk IO request at all times. So natively it can benefit from…
Post: Aligning IO on a hard disk RAID – the Benchmarks
June 9, 2011 By 13 Comments
… much benefit can we get from a proper IO alignment on a 4-disk RAID1+0 with 64k stripe element. I haven… 1333 MHz (0.8 ns) DIMM {OUT OF SPEC} Other … # Disk Schedulers And Queue Size ############################# sda | [deadline] 128 # RAID Controller ############################################ Controller… relevant to databases – random reads and random writes – IO alignment on a 4-disk RAID10 with standard 64k stripe element size makes…
Post: Modeling MySQL Capacity by Measuring Resource Consumptions
March 8, 2011 By 1 Comment
… CPU cycles, it may need disk IO. You may also need other resources such as network IO or memory to store temporary table… for your disk IO estimation. When you can divide it per number of “Questions” or “Com_select” to get amount of IO per… query. Lets assume it is restricted by IO performance (which it is in this disk) and having and the cost of system…
Post: Why Swapping is bad for MySQL Performance ?
January 18, 2010 By 11 Comments
… bad is it ? Should you count it same as normal Disk IO as the box is having or is it worse than… which again stops working as soon as page accesses cause disk IO. Escalated Locking/Latching If breaking of internal operations is not…-no to hold any critical locks while you’re doing disk IO as IOs take a long time. When system is swapping all…
Post: Using LoadAvg for Performance Optimization
December 4, 2006 By 5 Comments
…” state or in “uninterruptable sleep” state which typically corresponds to disk IO. You can also map LoadAvg to VMSTAT output – it is… CPU or it could be same 10 processes waiting on disk IO and you can see CPU utilization being close to zero… in the queue. Same true for pure Disk IO bound workload with small difference of disk not being replaceable (if you’re waiting…
Post: Is disk Everything for MySQL Performance ?
April 25, 2008 By 7 Comments
… many systems they have” on MySQL UC2008 Scalability Panel ? Indeed disks MAY be the most important part in your system performance… always the case. There are whole classes of systems where Disk performance is not that important – consider for example systems where… fixed amount of disk at your disposal and if you have BBU most likely data files is where all IO will go…
Post: Performance impact of complex queries
January 17, 2007 By 11 Comments
… much more than few milliseconds you would expect disk IO to take. Scheduling Issues OS Disk IO schedules may also “help” in this case… will be prioritized as they do not require disk head movement, compared to IO requests in random locations other threads are willing to take. Especially some older disk schedulers could be poor…
Post: Why MySQL could be slow with large tables ?
June 9, 2006 By 141 Comments
…. Now if you data fully on disk (both data and index) you would need 2+ IOs to retrieve the row which means… faster even if 50% of rows are accessed, while for disk IO bound accessess we might be better of doing full table… which combine index access with data access, saving you IO for completely disk bound workloads. There are certain optimizations in works which…
Post: Effect of adaptive_flushing
December 4, 2009 By 5 Comments
… and higher-than-previous-average rate of pages written to disk, which I find rather interesting Of course, there is also… question of system performance impact… More aggressive flushing means more disk IO and possibly other impact on the system, which could impact… am not really surprised. We can see a change in disk IO which mirrors the innodb pages written graph (shown above). I…
Post: How much overhead is caused by on disk temporary tables
August 16, 2007 By 26 Comments
… set (27 min 5.51 sec) VMSTAT: procs ———–memory———- —swap– —–io—- –system– —–cpu—— r b swpd free buff cache si so… as I would hope, at least on Linux Performance of Disk MyISAM tables may not scale proportionally with table size, even… MEMORY temporary tables can be 10-100 times faster than disk based MyISAM tables Hopefully MySQL will implement support of dynamic…
