Re: Asynchronous commit | Transaction loss at server crash

On 2010-05-20 22:26, Balkrishna Sharma wrote:
> But if we have write-through setting, failure before the cache can write to disk will result in incomplete transaction (i.e. host will know that the transaction was incomplete). Right
>
> Two things I need for my system is:1. Unsuccessful transactions with a notification back that it is unsuccessful is ok but telling it is a successful transaction and not being able to write to database is not acceptable (ever).2. My write time (random access time) should be as minimal as possible.
> Can a SSD with write-thru cache achieve this
>

A Battery Backed raid controller is not that expensive. (in the range of
1 or 2 SSD disks).
And it is (more or less) a silverbullet to the task you describe.

SSD "might" solve the problem, but comes with a huge range of unknowns
at the moment.

* Wear over time.
* Degraded performance in write-through mode.
* Degrading peformance over time.
* Writeback mode not robust to power-failures.

Plugging your system (SSD's) with an UPS and trusting it fully
could solve most of the problems (running in writeback mode).
But compared in complexity, I would say that the Battery backed
raid controller is way more easy to get right.

... if you had a huge dataset you were doing random reads into and
couldn't beef your system with more memory(cheapy) SSD's might
be a good solution for that.

--
Jesper