please read: Software Raid 5 and storage management

C

cornfield

Limp Gawd
Joined
Apr 22, 2005
Messages
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I read that the current linux kernel and the latest mdadm supports raid5 expansion. Has anyone had experience with this. How reliable is it? Is it pratical? I've read several tutorials found around the net none have been very noob friendly. I currently have Ubuntu 6.10 is it ready to run mdadm? does it already have it installed? If so how do I access it. Is there a program with a clean mdadm gui that includes raid expansion. Do any of the lighter server orientated distros (freenas, open filer etc.) support raid 5 expanion. I'm building a media server using 3 X 500gig SATA drives to start out with. Any and all information is welcome.

P.S. are there any suggestions on maintaing a fault tolreant media server with room for storage expansion? Is there a better way?

I am interested in Software Raid because read/write speeds aren't a huge concern because it's main function will be video streaming to no more then 2 users at a time and a Hardware Raid card would only serve as another point of possible failure and may become a problem if it needs to be replaced down the road due to it's proprietary nature.

Is there an efficient Linux or windows application that can be used to manage all shared or smb storage drives on a network.
 
I'm running a system on Gentoo that is software raid 5. I expanded 1 of my arrays the other month by adding 2 drives. 1 drive was to add more space. The other for a spare.

This is the what I did:
Code: 
echo check >> /sys/block/md0/md/sync_action   <<<<< change md0 if more than 1 array

Monitor the progress of the check with

watch -n .1 cat /proc/mdstat

This is to check the drives before expansion for errors, etc.

Once that is done.

Code: 
mdadm /dev/md0 --add /dev/hdd1 <<< change for what drive you add and array

This will bring it in as a spare.

Code: 
mycomputer ~ # cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 hda1[0] [b]hdd1[3](S)[/b] hdc1[2] hdb1[1]
      487424 blocks level 5, 64k chunk, algorithm 2 [4/4] [UUUU]

Then to make that drive active in the array.

Code: 
mdadm --grow /dev/md0 --raid-disks=4

Now wait for a long time for it to rebuild the array. You can watch its progress with the
watch -n .1 cat /proc/mdstat command. Adding in 1 250g drive to my array took
20 hours on a p4 2.6g machine to rebuild. Also make sure you have the kernel option to allow for a resize.


If you're running LVM2 and have one of the arrays as the physical volume, you just need to let LVM know that its physical volume has changed with the 'pvresize' command.

You'll end up with something like this:

Code: 
 --- Physical volume ---
  PV Name               /dev/md0
  VG Name               vg00
  PV Size               931.54 GB / not usable 0   
  Allocatable           yes 
  PE Size (KByte)       4096
  Total PE              238475
  Free PE               59619   <<<<<<<<<<<< more space to allocate to a logical volume
  Allocated PE          178856

I'm running a software raid system for similar reasons. Hardware raid is another point of failure and with Linux if my mobo or such craps out, I just move the arrays to another linux box and it will see the UUIDs of the drives and get the drives back into place. I've not had any performance issues with this setup and even have quicker file xfers with samba instead of normal windows shares.


Is there an efficient Linux or windows application that can be used to manage all shared or smb storage drives on a network.
Click to expand...

SWAT comes with Samba. Its a web based gui to manange Samba and settings. Just have to web to http://server:901 to access it.
 
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