[CentOS] Advice on partitioning a Dell MD1200 disk array

[Götz Reinicke]

Hi Tony,

because I suggest just something very general I post off list :)

From my POV as I'm currently facing similar setups with different
hardware rolling back from fine granular setups to simple 'bigger' less
complex configurations. (we do have 6 iscsi storages from 2TB (sun ZFS)
up to 32 TB)

	keep it small and simple! :)

I think you are very familiar with the general problems of big HW raids
and big filesystems like rebuild or check times, but splitting up and
adding more complex layers like multiple raids joining in lvm etc. makes
debugging and general handling very hard.

On the other hand, I checked and read a lot about filesystems the last
days being faced with serving user windows samba profiles with lot of
small files and big video/audio data etc.

Long story short:

I usually do one raidvolume per hardware raid box; e.g. we use 16*1TB
drives. Raid6 or Raid5 with spare. I did not notice big performance
differences.

I use LVM to make partitions or I prefer using just one big partition.

I tried xfs and ext4 and will go with ext4 as some test went better for
my setup and from what I read it looks not bad :)

I think you can combine block level devices (like multiple raid boxes)
by LVM into one bigger LV.

And last but not least: The CPU/RAM/Network of the host serving the
files is also very important! :)

I noticed, that the same iscsi storage got about 70MB/s on a new server
(xeon multicore), while on the old fileserver it just got up to 40MB/s.



	my2cents :) regards . Götz



May be worth reading:

http://www.techforce.com.br/news/linux_blog/lvm_raid_xfs_ext3_tuning_for_small_files_parallel_i_o_on_debian#.UEPSI1RqYso

http://monolight.cc/2011/02/linux-filesystems-small-file-performance-on-hdds/

http://unix.stackexchange.com/questions/28756/what-is-the-most-high-performance-linux-filesystem-for-storing-a-lot-of-small-fi

https://wiki.archlinux.org/index.php/Ext3

https://wiki.archlinux.org/index.php/Ext4#Tips_and_tricks



Am 04.09.12 13:10, schrieb Tony Molloy:
> 
> Hi,
> 
> I've just got possession of a Dell PE R720 with 2 MD1200 disk 
> enclosures.
> 
> Both MD1200 are fully populated with 12 x 3 TB disks
> 
> The system will basically be a student file-server running CentOS 6.x  
> serving various size files from small c programs to multi gigabyte 
> audio and video files over GB ethernet.
> 
> The first MD1200 will be configured as the NFS disk. The requirements 
> are for 6 fixed equally sized partitions, one for each cohort of 
> students. For this I was thinking of splitting the MD1200 into 2 RAID5 
> arrays with a hot spare each. Then partitioning each into 3 ext4 
> partitions.
> 
> The second MD1200 will be used to backup the first, using BackupPC and 
> for other storage purposes.
> 
> As I won't know the storage requirements for the "backup partition" 
> and they will probably change over time anyway. I was thinking of 
> using LVM for it. So how to partition the MD1200 for LVM. I don't want 
> to put all 12 disks in  a RAID5 and put a LVM volume on it. Can I 
> split it into 2 RAID5 and have a LVM volume spanning both.
> 
> Any suggestions. 
> 
> Just remember I'm due to retire at the end of this month so this will 
> be my last big job for the Dept. And due to financial constraints I 
> will not be replaced. So I will be handing this machine over to a co-
> worker who is basically a Windoze admin with only a basic knowledge of 
> Linux so nothing too fancy.  ;-)
> 
> Thanks,
> 
> Tony
> 
> 
> --
> 
> Tony Molloy
> 
> CTO, Dept. of Comp. Sci.
> University of Limerick
> Limerick.
> Ireland 
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> http://lists.centos.org/mailman/listinfo/centos
> 


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Götz Reinicke
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