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Date: Mon, 2 Dec 2013 11:57:01 -0800
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 <CAEDUwd1OAVoJ-bjoxcQFmPJdNnMXTTrc_CC_9wtHgPLC1fgMtg@mail.gmail.com>
Subject: Re: Recommended amount of free disk space for compaction
From: Robert Coli <rcoli@eventbrite.com>
To: "user@cassandra.apache.org" <user@cassandra.apache.org>
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On Thu, Nov 28, 2013 at 7:21 PM, Robert Wille <rwille@fold3.com> wrote:

> So here=92s my question. If Cassandra only compacts one table at a time,
> then I should be safe if I keep as much free space as there is data in th=
e
> largest table. If Cassandra can compact multiple tables simultaneously,
> then it seems that I need as much free space as all the tables put
> together, which means no more than 50% utilization.
>

If the number of SSTables is [x], then :

- "minor" compaction runs on 1-[x-1] SSTables (in practice, usually a
smaller number depending on config)
- "major" compaction runs on [x] SSTables

Unless you run a major compaction manually while using Size Tiered
Compaction, you are very unlikely to run a major compaction in normal
operation.

Level compaciton strategy has a different set of assumptions.

=3DRob

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<div dir=3D"ltr">On Thu, Nov 28, 2013 at 7:21 PM, Robert Wille <span dir=3D=
"ltr">&lt;<a href=3D"mailto:rwille@fold3.com" target=3D"_blank">rwille@fold=
3.com</a>&gt;</span> wrote:<br><div class=3D"gmail_extra"><div class=3D"gma=
il_quote">
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex"><div style=3D"font-size:14px;font-family:Cal=
ibri,sans-serif;word-wrap:break-word"><div>So here=92s my question. If Cass=
andra only compacts one table at a time, then I should be safe if I keep as=
 much free space as there is data in the largest table. If Cassandra can co=
mpact multiple tables simultaneously, then it seems that I need as much fre=
e space as all the tables put together, which means no more than 50% utiliz=
ation.</div>
</div></blockquote><div><br></div><div>If the number of SSTables is [x], th=
en :</div><div><br></div><div>- &quot;minor&quot; compaction runs on 1-[x-1=
] SSTables (in practice, usually a smaller number depending on config)</div=
>
<div>- &quot;major&quot; compaction runs on [x] SSTables</div><div><br></di=
v><div>Unless you run a major compaction manually while using Size Tiered C=
ompaction, you are very unlikely to run a major compaction in normal operat=
ion.</div>
<div><br></div><div>Level compaciton strategy has a different set of assump=
tions.</div><div><br></div><div>=3DRob =A0</div></div></div></div>

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