ZFS on Hardware RAID controller
aurfalien at gmail.com
Wed Feb 19 05:25:30 UTC 2014
Well, I think the best thing is to config a ZFS server for yourself.
Its one thing to read about it, but another to do it and you would most certainly be in a better position to sell ZFS once you know how it works through practice. The web is rich with ZFS info.
I’m speaking for personal experience.
On Feb 18, 2014, at 7:58 PM, freebsd at fongaboo.com wrote:
> I was speaking to someone else about this today, and it eventually became apparent that we were getting into a sort-of Abbott-and-Costello-Who's-on-First confusion... because apparently people can mean different things when they use the term 'JBOD'.
> What I have always meant when I say 'JBOD' is a (not really) RAID mode that simply concatenates the drives into one volume in a serial fashion, ie. 'spanning'. Most RAID controllers and RAID-enabled NAS units that I have interacted with in my life have offered this mode and referred to it as 'JBOD'.
> In this kind of mode, the motherboard and the OS still thinks it sees only a single volume. So now I am gathering that this is also not ideal for ZFS, since it would still not be aware of multiple physical volumes and be unable to optimize accordingly.
> I'm learning for the first time that sometimes 'JBOD' can also refer to each individual drive being mounted separately at least as far as the controller and the motherboard is concerned.
> I just want to confirm 100% that this is how you are recommending multiple drives be configured for ZFS. Because when I started the thread I was thinking of JBOD as 'spanning'.
> On Tue, 18 Feb 2014, Eitan Adler wrote:
>> On Tue, Feb 18, 2014 at 5:27 PM, <freebsd at fongaboo.com> wrote:
>>> When we spoke, you noted that when installing ZFS on multiple disks
>>> connected to a hardware RAID controller, it is best to config it to JBOD.
>> There are a few reasons for this.
>> (a) Hardware RAID serves as a single point of failure: if the
>> contoller dies you have neither disk
>> (b) As Andrew noted , using hardware RAID means that ZFS won't be able
>> to tell which disk is which. The ZFS management tools won't work as
>> expected (they will show only one disk).
>> (c) Since ZFS implements RAID itself it can use knowledge about the
>> physical disks for better performance
>> Also see: https://en.wikipedia.org/wiki/ZFS#ZFS_and_hardware_RAID
>>> I tried to explain this to a colleague, but they were skeptical. Would you
>>> (or anyone) be willing to give me a one or two line sales-pitch on
>> "ZFS does RAID better than the controller."
>>> why one
>>> should abandon traditional notions of RAID performance in favor of allowing
>>> ZFS to do disk management?
>> The goal isn't to give up on RAID but move its implementation to ZFS.
>> Eitan Adler
>> Source, Ports, Doc committer
>> Bugmeister, Ports Security teams
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