Debian root partition greater than 2TB

2

I have two internal hard drives: a 4TB drive and a 750GB drive. After selecting RAID0 and installing Debian (wheezy) to a single partition, I ran fdisk -l which reported that the size of my root partition (/dev/sda1) was 1.4T. So, I've got a couple of questions....

1) I know that fdisk only allows up to 2TB so even if my (4TB + 750GB) drive was being restricted to 2TB, what happened to the other 0.6TB? Remember, I installed everything to one partition.

2) My ultimate goal is to have everything on a single 4TB partition. I've read about parted but everything I read relates to partitioning and mounting a non-bootable partition. This doesn't apply to me as I'm using a single partition which contains /boot. What are my options?

Ash

Posted 2013-07-29T06:48:58.887

Reputation: 563

Could you clarify your question. 1. How are you using a raid 0 with two different sized drives? 2. Is your drive GPT or MBR, – spuder – 2013-07-29T06:57:54.463

What is your kernel version ? With v0.90 raid superblock and kernel <3.1, you have severe limitations. see : https://raid.wiki.kernel.org/index.php/RAID_superblock_formats

– mveroone – 2013-07-29T07:55:46.730

@Kwaio: Kernel is 3.2.0-4-686-pae. – Ash – 2013-07-29T08:00:58.170

Is your OS 64bit ? Is it up to date ? specifically, HBA drivers... – mveroone – 2013-07-29T08:02:41.463

@spuder: Why shouldn't I be able to use raid 0 with two different sized drives? It's raid 0 (not raid 1), so there's no mirroring. The disks can be any size. I'm sure it's MBR. Don't think GPT would give me this problem to begin with. – Ash – 2013-07-29T08:04:01.433

A Raid0 array is of the size of its smallest drive. That is how it works, blocs are split between all drives. – mveroone – 2013-07-29T08:05:20.693

1@spuder: I see. Well the SAS configuration utility on my Dell server gave me two options to set up the RAID array: mirroring and striping. I chose striping. I thought that would have given me maximum space but I guess I was wrong. You're correct. I've ended up with 2 * 750GB = 1.5TB worth of space. – Ash – 2013-07-29T08:14:14.880

You could check if your dell server's raid card has JOBD. That sounds like what you are trying to accomplish, however I would discourage raid or JOBD in this setup because loosing one drive looses both. Instead consider using the 750 for the OS, and the 2tb for your data. – spuder – 2013-07-29T08:18:57.013

I've checked every menu option during boot and I can't remember any reference to JOBD. I don't think I can do what you've suggested spuder as the configuration requires me to choose either mirroring or striping. I can't have a single hdd either. I think my best bet is to replace the smaller (750GB) drive with one of the same size as the bigger one (4TB). I'd then have to re-install the OS with /boot under a different partition and finally run parted to create a partition greater than 2TB.

Please suggest better alternatives if there are any. – Ash – 2013-07-29T08:23:03.543

In both cases, remember stripping isn't safe. Either schedule regular backups or avoid storing data you don't want to loose there. – mveroone – 2013-07-29T08:25:51.250

Answers

0

Just to sum up what we came with in the comments, here is your problem :

You are doing stripping (alias RAID-0) over two drives :

  • a 4 TB one
  • a 750 GB one

The size used on every drive of a RAID0 array is equal to the size of its smallest drive. Thus your array wil be 2*750 GB = 1.5GB. Removing a bit of overhead and GiB/GB confusion, this came up with a 1.4TB array.

From there your only option is to use your drives separatly (which you seem to be unable to do using your SAS card) or replace the small drive by a 4TB one.

Anyway, remember Stripping is unsafe as any drive failure will result in the loss of data stored on both disks, because any block of data is split between both drives.

mveroone

Posted 2013-07-29T06:48:58.887

Reputation: 1 752

1One more comment: Once these problems are dealt with, GPT is more-or-less required to make use of an over-2TiB disk. Thus, the MBR partitioning should be scrapped and parted or gdisk (not fdisk, except very recent versions) should be used to set the disk up with GPT. Also, I do not generally recommend using a single partition on such a big disk. At the very least, root (/) should be separated from user data (usually in /home for workstations; often in /var on servers), and a separate swap partition is often in order. – Rod Smith – 2013-07-29T14:18:31.433

For some reason, swap turned out to be in a separate partition by default. The server is primarily used to backup another server and it is itself backed up on a regular basis. So there's no need for home directories and I am not worried about data loss. Thanks a lot for all the responses. – Ash – 2013-07-30T02:37:31.970

Asked: 2013-07-29T06:48:58.887

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Active: 2013-07-29T08:28:57.797