[TYPO3-dev] TYPO3 4.1 INNODB

[Steffen Kamper]

"Dmitry Dulepov" <9f4eetb02 at sneakemail.com> schrieb im Newsbeitrag 
news:mailman.1.1172743306.32189.typo3-dev at lists.netfielders.de...
> Hi!
>
> Steffen Müller wrote:
>> Dmitry, could you please explain why "InnoDB is more stable than MyISAM
>> and prevents database corruption at peaks"?
>> I did not yet read about that.
>
> Mysql does its best to prevent simultaneous writes to myisam tables. It 
> relies on locks (normally file locks) when user tries to write to myisam 
> table. However this does not always work as expected, especially at peak 
> hours. Sometimes at least two writes still happen and table immediately 
> becomes corrupted. Search English list archives, you will find several 
> questions about corrupted tables. I had those too several times, when 
> mysql has to process over 700qps (as mytop reports). At one point crashes 
> started to appear every day. I searched inet and found various posts about 
> it that generally recommended to move to innodb. I did that more than half 
> a year ago and did not have *any* table corruptions on those tables even 
> though load increased.
>
> InnoDb uses row transaction internally even if user did not start it 
> explicitly. While myisam locks the whole table at write, innodb locks only 
> space for one row. See the advantage? You can have many clients writing to 
> table at once with InnoDB, who are well separated. But you cannot have 
> more than one write to myisam table (performance killer!) and if it 
> happens, your table dies immediately!
>
> InnoDb, of course, has its disadvantages. If "select count(*) from table" 
> takes very little time/resources on myisam (because count is stored in 
> table itself), innodb has to really count rows. But this is not a problem 
> for typo3 because typo3 does not have such queries :)
>
> But there is one more advantage for Innodb. Myisam keeps indexes 
> separately from row data. Thus if row pointer is found, myisam engine has 
> to do one  more seek to data. Innodb keeps indexes together with rows, so 
> it does not have to seek again.
>
> In general, I think innodb is much better for typo3 than myisam. I really 
> did several days of research before switching.
>
> -- 
> Dmitry Dulepov
>
> Web: http://typo3bloke.net/
> Skype: callto:liels_bugs
>
> "It is our choices, that show what we truly are,
> far more than our abilities." (A.P.W.B.D.)

thanks Dmitry for this explanations. Sometimes i would like to copy such 
things into a wiki, the discussions here inside are mostly packed with 
Acknowledge !

vg  Steffen