ZFS - thanks

[Dan Naumov]

On Thu, Jul 9, 2009 at 3:30 PM, Nenhum_de_Nos<matheus at eternamente.info> wrote:
>
> On Thu, July 9, 2009 09:25, Dan Naumov wrote:
>> On Thu, Jul 9, 2009 at 3:17 PM, Nenhum_de_Nos<matheus at eternamente.info>
>> wrote:
>>>
>>> On Thu, July 9, 2009 08:25, Patrick M. Hausen wrote:
>>>> Hi, all,
>>>>
>>>> I just wanted to say a big big thank you to Kip and all the
>>>> developers who made ZFS on FreeBSD real.
>>>>
>>>> And to everyone who provided helpful comments in the
>>>> last couple of days.
>>>>
>>>> I had to delete and rebuild my zpool to switch from a
>>>> 12-disk raidz2 to two 6-disk ones, but yesterday I could
>>>> replace the raw devices with glabel devices and practice
>>>> replacing a failed disk at the same time. ;-)
>>>>
>>>> So now we have this setup:
>>>>
>>>>       NAME               STATE     READ WRITE CKSUM
>>>>       zfs                ONLINE       0     0     0
>>>>         raidz2           ONLINE       0     0     0
>>>>           label/disk100  ONLINE       0     0     0
>>>>           label/disk101  ONLINE       0     0     0
>>>>           label/disk102  ONLINE       0     0     0
>>>>           label/disk103  ONLINE       0     0     0
>>>>           label/disk104  ONLINE       0     0     0
>>>>           label/disk105  ONLINE       0     0     0
>>>>         raidz2           ONLINE       0     0     0
>>>>           label/disk106  ONLINE       0     0     0
>>>>           label/disk107  ONLINE       0     0     0
>>>>           label/disk108  ONLINE       0     0     0
>>>>           label/disk109  ONLINE       0     0     0
>>>>           label/disk110  ONLINE       0     0     0
>>>>           label/disk111  ONLINE       0     0     0
>>>>
>>>> which will get another enclosure with 6 750-GB-disks, soon.
>>>>
>>>> I really like the way I can manage storage from the operating
>>>> system without propriatary controller management software or
>>>> even rebooting into the BIOS.
>>>>
>>>> Kind regards,
>>>> Patrick
>>>
>>> I've always been curious about this. is said not good to have many disks
>>> in one pool. ok then. but this layout you're using in here will have the
>>> same effect as the twelve disks in only one pool ? (the space here is
>>> the
>>> sum of both pools ?)
>>
>> Having an enormous pool consisting of dozens of disks is not the
>> actual problem. Having the pool consist of large (> 9 disks)
>> raidz/raidz2 "groups" is.
>>
>> A single pool consising of 5 x 8 disk raidz (40 disks total) is fine.
>> A single pool consisting of a 40 (or any amount bigger than 9) disk
>> raidz is not.
>
> thanks. but the final file system in both these cases are the same ? (what
> I'll see in df -h).

No.

A single pool consisting of 5 x 8 disk raidz will have 40 disks total,
35 disks worth of space
A single pool consisting of 5 x 8 disk raidz2 will have 40 disks
total, 30 disks worth of space

A single 40 disk raidz (DO NOT DO THIS) will have 40 disks total, 39
disks worth of space and will definately explode on you sooner rather
than later (probably on the first import, export or scrub).

- Sincerely,
Dan Naumov