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Date: Fri, 23 Dec 2011 10:15:35 -0200
From: alexandre - aldeia digital <adaldeia@gmail.com>
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Subject: Re: Postgresql 9.0.6 Raid 5 or not please help.
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> I'm not so confident that a RAID-1 will win over a single disk. When it
> comes to writes, the latency should be ~50 higher (if both disk must
> sync), since the spindles are not running synchronously. This applies to
> softraid, not something like a battery-backend raid controller of course.
>
> Or am I wrong here?
>

Software RAID-1 in Linux, can read data in all disks and generally 
increase a lot the data rate in reads. In writes, for sure, the overhead 
is great compared with a single disk, but not too much.