LinuxQuestions.org
Latest LQ Deal: Complete CCNA, CCNP & Red Hat Certification Training Bundle
Go Back   LinuxQuestions.org > Forums > Linux Forums > Linux - Server
User Name
Password
Linux - Server This forum is for the discussion of Linux Software used in a server related context.

Notices


Reply
  Search this Thread
Old 06-14-2007, 10:32 AM   #1
aunquarra
LQ Newbie
 
Registered: Jan 2005
Distribution: Slackware 10.1
Posts: 28

Rep: Reputation: 15
software raid 10 (yes, another raid question)


I'm looking at having two different types of servers that both perform the same functionality, but one has a higher build budget. I had planned on doing software raid (typical linux stuff) on the small-budget system and a good 3ware card for the higher-budget one.

With four drive bays in these machines, and SATA drives as cheap as they are, I decided to go ahead and fill them. I wanted to do raid 1+0 with the hardware solution, but I'm wondering if the linux raid performs well enough with raid 10 to go ahead and do it on the software side, too.

I've always just done raid 1 with linux in the past, but these are going to be database heavy applications, so I need the availability and reliability, yadda yadda yadda. So can anyone fill me in on their experiences/opinions on software raid 1+0 in linux (specifically CentOS, though I don't think it makes much difference).
 
Old 06-14-2007, 08:17 PM   #2
3point2
LQ Newbie
 
Registered: Jan 2006
Distribution: Slackware 11.0
Posts: 23

Rep: Reputation: 15
Hi,

I set up a server with four hard drives and software raid 10 a month or two ago. Although I can't say it's been pushed very hard yet, it's been stable so far. I did get a kernel panic at one point while setting it up, but I was also running a patched VMware server on an XFS filsystem, and since both of those are also new to me I can't automatically blame the software RAID. Performance-wise I haven't run any benchmarks, but it seems 'fast', subjectively speaking

My biggest issue was deciding how to partition the disks and which partitions to use to create the RAID 10 array. I wanted to be able to have any single disk (or possibly two) fail and still have a fully functional and bootable system. With hardware RAID, this is no big deal since the RAID is totally transparent to software.

The problem with software RAID 10 is that no boot loader can read off a software RAID 10 array! All grub or lilo sees is four drives with raid 10 data on them, which is as good as garbage to a boot loader. In order to achieve the reliability I wanted, it was necessary to create a small partition at the start of each hard drive. I used all four of them to create a single RAID 1 array, and installed GRUB into the MBR of each hard drive. The remaining four large partitions made up the RAID 10 array. The RAID 1 device is mounted under /boot, so any kernel upgrades are mirrored on all drives. The boot loader can then read the kernel off any of the four mirrored partitions. This setup also required that I created a custom initrd with the raid10 module included, since the kernel then has to mount the RAID 10 array as its root filesystem.

No distribution I know of has an installer that supports a RAID 10 root partition, so this all has to be done by hand and can be a little tricky. By the way, Fedora Core 6 is the OS I installed.

I would recommend you use a fifth extra hard drive with a working linux installation that you can boot off. This gives you a good place to configure the other drives from. I was in the unfortunate position of doing all the above with only those four hard drives and a cdrom drive to play with! It is doable though, so if you'd like a more detailed description of how that's done, just ask.

Good luck!
 
Old 06-14-2007, 09:46 PM   #3
aunquarra
LQ Newbie
 
Registered: Jan 2005
Distribution: Slackware 10.1
Posts: 28

Original Poster
Rep: Reputation: 15
Thanks so much for that. It seems like a lot of hassle, and unfortunately, I only have four drive bays to work with. I don't know that the extra space will really be worth it...

I guess I'll do raid 10 when I have the budget for a hardware raid solution, but otherwise, I guess I'll do raid 1 over three drives for data and a small drive in the fourth slot for the OS...

3-way raid 1 seems like severe overkill, but at least it'll sound good from a sales perspective...
 
Old 06-15-2007, 06:28 PM   #4
3point2
LQ Newbie
 
Registered: Jan 2006
Distribution: Slackware 11.0
Posts: 23

Rep: Reputation: 15
Just make sure that any RAID card you buy for the RAID 10 is true, pure, absolute, 100% hardware RAID. I ended up in the unfortunate situation I described above after buying a motherboard that could apparently do RAID 10. After configuring everything in the BIOS I was shocked to see that linux could still see four hard drives! It was only then that I found out that many new "hardware" RAID solutions need an additional driver (only windows drivers on the supplied CD, of course). I guess the price was too good to be true for a reason
 
  


Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off



Similar Threads
Thread Thread Starter Forum Replies Last Post
Why can't I mount this md0 raid? (mdadm and software raid) cruiserparts Linux - Software 35 01-05-2013 04:35 PM
software raid 0 and raid 5: which chunk size to choose? malo_umoran Linux - General 2 02-26-2007 07:19 PM
cheap sata raid or software raid? taiwf Linux - Hardware 4 10-13-2006 11:58 AM
Can fake raid be converted to linux software raid? jmacdonald801 Linux - General 3 01-30-2005 01:33 PM
moving system from ide software raid to new box with scsi raid ftumsh Linux - General 0 10-28-2003 10:34 AM

LinuxQuestions.org > Forums > Linux Forums > Linux - Server

All times are GMT -5. The time now is 10:53 PM.

Main Menu
Advertisement
My LQ
Write for LQ
LinuxQuestions.org is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
Syndicate
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
Facebook: linuxquestions Google+: linuxquestions
Open Source Consulting | Domain Registration