Dataset or Volume (ZFS in NAS4Free)

Discussion in 'Storage & Backup' started by robertgd, Oct 6, 2012.

  1. robertgd

    robertgd Member

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    Have installed the latest version of NAS4Free (FreeNAS 7 continuation)

    I'm fairly new to ZFS and Unix/BSD in general. So far I've set up my ZFS pool in RAIDZ of 5x 2TB drives - giving me 9.06T - however I think only 7.5TB would be usable? It doesn't really say anywhere.

    Now I'm a bit confused on the differences between volumes and datasets. I have looked on the wiki but there doesn't seem to be much information there.

    What I'd ultimately like is the ZFS pool to have two usable volumes. One called "media" which would be around 5-6TB, and one called "files" which would use the remainder (1-2TB?) that are shared out.

    I'm not sure if I should be created a single volume, and two datasets? Or two volumes and no datasets?

    I tried mucking around but didn't get very far. I managed a single volume called data, but I'd really prefer two separate ones. So I've deleted everything (except for the zpool) so I can start from scratch.

    Also I've now noticed this:
    Name Size Used Free Capacity Dedup Health AltRoot
    data 9.06T 5.00T 2.13T 0% 1.00x ONLINE -

    I'm not sure why it's saying used 5T? There is nothing on the drives, they are blank.

    Some help would be much appreciated.
     
  2. CiPHER_nl

    CiPHER_nl Member

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    A volume in ZFS context means a ZVOL; a virtual harddrive that can be used to put other filesystems on. For example if you use iSCSI, you give a virtual harddrive of x gigabyte to your Windows desktop which puts its own NTFS filesystem on top of that.

    Safer and better is to use ZFS filesystems, which probably is what you want.

    Your pool 'tank' always contains a filesystem by the same name as the pool, but you can create as many as you want. Filesystems are special directories and share all free space available in the pool.

    It probably says 5TB because that is actually in use; you created a virtual harddrive (ZVOL) of a large size and ZFS doesn't know or care what it contains. I suggest you destroy the volume and create filesystems instead!
     
  3. LostBenji

    LostBenji Member

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    My understanding is the Nas4FREE is ZFS (v28), am I wrong or missing something????

    I ask because in light of my recent dealing with HighPoint, I am looking at HBA's and Expander's to use with Nas4FREE.
     
  4. CiPHER_nl

    CiPHER_nl Member

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    I mean it is safer to use ZFS filesystems instead of ZFS volumes and using iSCSI to connect your Windows/Linux to it and put NTFS filesystem on that, stored on the ZFS volume on the NAS4Free system.

    A filesystem is created with 'zfs create tank/newfilesystem' and acts much like a directory. A volume cannot be browsed on the server; it is like a virtual harddrive that can be used for special purposes like iSCSI. So it is probably not what you want.

    HighPoint is a hardware RAID controller which is not suitable for use with ZFS or other software RAID, because HighPoint controls the disks and not ZFS. ZFS likes to be as close to the disks as possible, to prevent firmware from hardware RAID from tampering. Especially when bad sectors occur you do not want to use a hardware RAID controller.

    What you want is a HBA controller without RAID. The most common and well available option right now is IBM M1015. It works in most operating systems though with FreeBSD you require a modern driver, not sure how up to date NAS4Free is. But at least ZFSguru (also BSD based) works great with this controller. It is also cheap and available across the globe. You do need/want to flash it with IT firmware, which is discussed over here:
    http://www.servethehome.com/ibm-serveraid-m1015-part-4/
     
  5. LostBenji

    LostBenji Member

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    Yeah, the LowPoint is being RMAed so won't be an issue. Either a HBA is going in with ZFS in mind or HW RAID like the Intel (LSI 2108) or adaptec 6805 with expanders.

    I have just finished testing Nas4FREE and after repeated file transfer fails, I am not impressed and will look at other options like staying with Winblows and HW-RAID. Good chance it is my setting up of Nas4FREE but their documentation leaves a lot to be desired if your not strong with alternates. Sick of having to Google basic settings....
     
  6. young_einstein

    young_einstein Member

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    Easily done.

    The first option is what you're after.
    IE - You just want all your disks as a single ZFS pool (or volume as they refer to it).

    See http://doc.freenas.org/index.php/Volumes#Volume_Manager

    From there, you just create datasets for your media / files.

    See http://doc.freenas.org/index.php/Volumes#Creating_ZFS_Datasets

    I realise that the documentation is based on FreeNAS, but I'm sure that it's still (largely) the same with NAS4Free.

    NOTE: I wouldn't be bothering to set quotas / reservations on the datasets either.

    One of the beauties of ZFS is that all your data is backed by a common storage pool, and everything just grows / resizes as needed.
    IE - Each dataset has the (potential) capacity of your entire storage pool, so there's absolutely no need to set any arbitrary limits on them.

    It's a side effect of how you tried to configure things initially.
    Provided that you don't have anything on there which you need to keep (which is what you've said), the easiest way to fix it is to just delete your entire pool and start again from scratch.
     
    Last edited: Oct 13, 2012
  7. CiPHER_nl

    CiPHER_nl Member

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    Appears you are right. But that is so misleading. If you call a pool a volume, then what do you call a volume? FreeNAS is essentially confusing volumes with pools. This makes it all the more difficult to understand ZFS for people new to this great filesystem.
     

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