From: Jesper Krogh <jesper@krogh.cc>
To: Balkrishna Sharma <b_ki@hotmail.com>
Cc: scott.marlowe@gmail.com
Cc: pgsql-admin@postgresql.org
Subject: Re: Asynchronous commit | Transaction loss at server crash
Date: Thu, 20 May 2010 22:33:48 +0200
Message-ID: <4BF59CAC.9040200@krogh.cc> (raw)
In-Reply-To: <BAY149-w464B3415293316B1A6739AF0E30@phx.gbl>
References: <BAY149-w7E2586A2E044680536BD8F0E30@phx.gbl>
<AANLkTimxy4_ecy3MnHYTNeWcVOrIQdJIm1_nutxHEBd4@mail.gmail.com>
<BAY149-w47C0EFBE3720C0DA258E4AF0E30@phx.gbl>
<AANLkTinT3Tx3nNb4YME6j58Edp45Q9pgCyVRkZYTnXU1@mail.gmail.com>
<BAY149-w464B3415293316B1A6739AF0E30@phx.gbl>
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
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To: pgsql-admin@postgresql.org
Cc: jesper@krogh.cc, b_ki@hotmail.com, scott.marlowe@gmail.com
Subject: Re: Asynchronous commit | Transaction loss at server crash
In-Reply-To: <4BF59CAC.9040200@krogh.cc>
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