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Date: Mon, 23 Sep 2013 11:21:15 -0700
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Subject: Re: Commit log and data separation on SSD
From: Robert Coli <rcoli@eventbrite.com>
To: "user@cassandra.apache.org" <user@cassandra.apache.org>
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On Sun, Sep 22, 2013 at 4:02 PM, Shahryar Sedghi <shsedghi@gmail.com> wrote:

> This my first SSD experience. With  normal disks we separate commit log
> from data. We have 2 SSDs dedicated to Cassandra  I was wondering if we
> gain a better performance  if we put commit  log in one and data in
> another, or just use raid 0 to have both SSDs combined.
>

The primary win from separation comes when your head does not move while
appending. As your SSDs have no heads, you do not get this win.

=Rob

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<div dir=3D"ltr">On Sun, Sep 22, 2013 at 4:02 PM, Shahryar Sedghi <span dir=
=3D"ltr">&lt;<a href=3D"mailto:shsedghi@gmail.com" target=3D"_blank">shsedg=
hi@gmail.com</a>&gt;</span> wrote:<br><div class=3D"gmail_extra"><div class=
=3D"gmail_quote">
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex"><div dir=3D"ltr"><div><div>This my first SSD=
 experience. With=A0 normal disks we separate commit log from data. We have=
 2 SSDs dedicated to Cassandra=A0 I was wondering if we gain a better perfo=
rmance=A0 if we put commit=A0 log in one and data in another, or just use r=
aid 0 to have both SSDs combined.<br>
</div></div></div></blockquote><div><br></div><div>The primary win from sep=
aration comes when your head does not move while appending. As your SSDs ha=
ve no heads, you do not get this win.</div><div><br></div><div>=3DRob=A0</d=
iv>
</div></div></div>

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