Re: [Moosefs-users] Questions about MooseFS before putting it onthe production env

[颜. <rw...@12...>]

Unfortunately, if the master crashed when some client is writing data to MFS, 
the data is lost absolutely.
If we storage VM disk img file with MFS, when master crash, this img file was destroyed and u can't boot this vm with that img file.
That means, we lost this vm permanently.





发件人： Michal Borychowski 
发送时间： 2011-04-15  20:19:37 
收件人： 'ailms' 
抄送： 'moosefs-users' 
主题： Re: [Moosefs-users] Questions about MooseFS before putting it onthe production env 
Hi Bob!
 
My replies are in the text. And for start please read this article:
http://www.moosefs.org/news-reader/items/metadata-ins-and-outs.html
 
 
From: ailms [mailto:ai...@qq...] 
Sent: Thursday, April 14, 2011 5:52 PM
To: moosefs-users
Subject: [Moosefs-users] Questions about MooseFS before putting it on the production env
 
Dear guys,
We are plan to use moosefs as our store mechanism, which will be more than 5TB off-line command log. 
But now we have someconcern, Please find my queries below:
-----
1.  is there any plan about resolving the single-point failure of master ?
[MB] Please check a project developed by Thomas Hatch: https://github.com/thatch45/mfs-failover 
It still needs some improvements but is a great way to test the failovers. And Thomas needs some beta testers.
 
2.  The data will lost if master crash without dumping metadata from RAM into disk,is it right?
[MB] Changelogs are saved continuously on the fly, there is very little probability you would lose your data upon crash of the master server
 
3.  How can I know which data were lost if the question #2 happend?
[MB] When you make a recovery process of metadata you would know if it was successful or not
 
4.  Dose the master only caches metadata read-only or will update the data in RAM and flush to disk periodically?
[MB] The changes to metadata are saved to changelogs continuously on the fly
 
5.  Are the change logs based on the metadata.mfs.back or the data in RAM ?
[MB] We can consider them as based on RAM
 
6.  Can I change the default dumpling behaviour for master metadata from per hour to user defined value? Such as 30 min?
[MB] As far as I remember, yes you can
 
7.  How can we make sure no data lost at any time with HA（KeepAlived）+ DRBD + mfs solution ?
[MB] We have not done such tests. Please first check a solution given in question 1.
 
8.  The mfsmetaloggr didn't re-connect automatically even though I had stoped and restarted the mfsmater, can only by manual?
[MB] Should have reconnected automatically. What was your environment? 
 
9.  which option in mfsmaster.cfg controls the rotation of changelog ? according to the size ?  or each time when mfsmaster dump the metadata ?
[MB] Please see „man mfsmaster.cfg” – you should have all the options listed
 
 
Kind regards
Micha┅ Borychowski 
MooseFS Support Manager
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Gemius S.A.
ul. Wo┅oska 7, 02-672 Warszawa
Budynek MARS, klatka D
Tel.: +4822 874-41-00
Fax : +4822 874-41-01
 
 

Any help will be appreciated. Looking forward your answer.

Best Regard
Bob Lin