Can I delete old journaling files? - mongodb-user

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Message from discussion Can I delete old journaling files?
Date: Fri, 2 Nov 2012 08:26:46 -0700 (PDT)
From: Louisa Berger <louisa.ber...@10gen.com>
To: mongodb-user@googlegroups.com
Message-Id: <7060c631-64b8-4d1e-a7ec-0296f20fa63c@googlegroups.com>
In-Reply-To: <cee07135-90fb-4e4d-aced-6ca21a256b6a@googlegroups.com>
References: <a3e98607-416b-4479-bd07-5c0dfee52379@googlegroups.com>
 <cee07135-90fb-4e4d-aced-6ca21a256b6a@googlegroups.com>
Subject: Re: Can I delete old journaling files?
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Hi Justin,

So the prealloc files are preallocated journal files. There are also *in use
* journal files ( they look like j._X ). Mongod creates these so that  when 
the current journal file runs out of space, the next file is already 
allocated. This can be aster than doing on-demand allocation. You can read 
more about it here<http://www.mongodb.org/display/DOCS/Journaling+Administration+Notes#JournalingAdministrationNotes-PreallocFiles%28e.g.journal%2Fprealloc.0%29>
.

These files don't contain any data, so it's safe to remove them. However, 
if you restart mongod with journaling set to 'on', it will recreate them if 
they are missing. 


On Friday, November 2, 2012 3:19:39 AM UTC-4, Justin Meltzer wrote:
>
> Also I did not have any sort of database crash. I cleanly shutdown my 
> database.
>
> Plus I'd be curious to learn what these prealloc.X files are for.
>
> On Friday, November 2, 2012 3:15:36 AM UTC-4, Justin Meltzer wrote:
>>
>> First off, I'm fairly new to mongodb and journaling so I do not fully 
>> understand exactly how journaling works.
>>
>> I'm trying to change the dbpath after having already used a previously 
>> different dbpath. I followed the ec2 quickstart guide here: 
>> http://www.mongodb.org/display/DOCS/Amazon+EC2+Quickstart#AmazonEC2Quickstart-Prerequisitesand am now copying over my data to a filesystem that is backed by RAID 10. 
>> Copying over my regular database files worked fine, but the prealloc.X 
>> files in the journal directory are completely filling up the /journal 
>> partition. Is it ok to delete these files, and will journaling still work 
>> if I do?
>>
>
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<div><span style=3D"color: rgb(76, 58, 44); font-family: helvetica, arial, =
sans-serif; line-height: 21.316667556762695px; background-color: rgb(243, 2=
44, 235); ">Hi Justin,</span></div><div><span style=3D"color: rgb(76, 58, 4=
4); font-family: helvetica, arial, sans-serif; line-height: 21.316667556762=
695px; background-color: rgb(243, 244, 235); "><br></span></div><div><span =
style=3D"color: rgb(76, 58, 44); font-family: helvetica, arial, sans-serif;=
 line-height: 21.316667556762695px; background-color: rgb(243, 244, 235); "=
>So the prealloc files are preallocated journal files. There are also <i>in=
 use</i>&nbsp;journal files ( they look like j._X ). Mongod creates these s=
o that &nbsp;when the current journal file runs out of space, the next file=
 is already allocated. This can be aster than doing on-demand allocation.&n=
bsp;</span><span style=3D"background-color: rgb(243, 244, 235); color: rgb(=
76, 58, 44); font-family: helvetica, arial, sans-serif; line-height: 21.316=
667556762695px; ">You can read more about it </span><a href=3D"http://www.m=
ongodb.org/display/DOCS/Journaling+Administration+Notes#JournalingAdministr=
ationNotes-PreallocFiles%28e.g.journal%2Fprealloc.0%29" style=3D"font-famil=
y: helvetica, arial, sans-serif; line-height: 21.316667556762695px; ">here<=
/a><span style=3D"background-color: rgb(243, 244, 235); color: rgb(76, 58, =
44); font-family: helvetica, arial, sans-serif; line-height: 21.31666755676=
2695px; ">.</span></div><div><span style=3D"color: rgb(76, 58, 44); font-fa=
mily: helvetica, arial, sans-serif; line-height: 21.316667556762695px; back=
ground-color: rgb(243, 244, 235); "><br></span></div><div><span style=3D"co=
lor: rgb(76, 58, 44); font-family: helvetica, arial, sans-serif; line-heigh=
t: 21.316667556762695px; background-color: rgb(243, 244, 235); ">These file=
s don't contain any data, so it's safe to remove them. However, if you rest=
art mongod with journaling set to 'on', it will recreate them if they are m=
issing.&nbsp;</span></div><div><span style=3D"color: rgb(76, 58, 44); font-=
family: helvetica, arial, sans-serif; line-height: 21.316667556762695px; ba=
ckground-color: rgb(243, 244, 235); "><br></span></div><div><span style=3D"=
color: rgb(76, 58, 44); font-family: helvetica, arial, sans-serif; line-hei=
ght: 21.316667556762695px; background-color: rgb(243, 244, 235); "><br></sp=
an></div>On Friday, November 2, 2012 3:19:39 AM UTC-4, Justin Meltzer wrote=
:<blockquote class=3D"gmail_quote" style=3D"margin: 0;margin-left: 0.8ex;bo=
rder-left: 1px #ccc solid;padding-left: 1ex;">Also I did not have any sort =
of database crash. I cleanly shutdown my database.<div><br></div><div>Plus =
I'd be curious to learn what these prealloc.X files are for.<br><br>On Frid=
ay, November 2, 2012 3:15:36 AM UTC-4, Justin Meltzer wrote:<blockquote cla=
ss=3D"gmail_quote" style=3D"margin:0;margin-left:0.8ex;border-left:1px #ccc=
 solid;padding-left:1ex">First off, I'm fairly new to mongodb and journalin=
g so I do not fully understand exactly how journaling works.<div><br></div>=
<div>I'm trying to change the dbpath after having already used a previously=
 different dbpath. I followed the ec2 quickstart guide here:&nbsp;<a href=
=3D"http://www.mongodb.org/display/DOCS/Amazon+EC2+Quickstart#AmazonEC2Quic=
kstart-Prerequisites" target=3D"_blank">http://www.mongodb.org/<wbr>display=
/DOCS/Amazon+EC2+<wbr>Quickstart#<wbr>AmazonEC2Quickstart-<wbr>Prerequisite=
s</a> and am now copying over my data to a filesystem that is backed by RAI=
D 10. Copying over my regular database files worked fine, but the prealloc.=
X files in the journal directory are completely filling up the /journal par=
tition. Is it ok to delete these files, and will journaling still work if I=
 do?</div></blockquote></div></blockquote>
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