Re: [gentoo-user] dmraid, mdraid, lvm, btrfs, what?

[Florian Philipp <lists@binarywings.net>]

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Am 29.11.2011 19:39, schrieb Michael Mol:
> On Tue, Nov 29, 2011 at 1:20 PM, Florian Philipp <lists@binarywings.net> wrote:
>> Am 29.11.2011 14:44, schrieb Michael Mol:
>>> On Tue, Nov 29, 2011 at 2:07 AM, Florian Philipp <lists@binarywings.net> wrote:
>>>> Am 29.11.2011 05:10, schrieb Michael Mol:
>>>>> I've got four 750GB drives in addition to the installed system drive.
>>>>>
>>>>> I'd like to aggregate them and split them into a few volumes. My first
>>>>> inclination would be to raid them and drop lvm on top.  I know lvm well
>>>>> enough, but I don't remember md that well.
>>>>>
>>>>> Since I don't recall md well, and this isn't urgent, I figure I can look
>>>>> at the options.
>>>>>
[...]
>>>> What kind of RAID level do you want to use, 10 or 5? You
>>>> can also split it: Use a smaller RAID 10 for performance-critical
>>>> partitions like /usr and the more space-efficient RAID 5 for bulk like
>>>> videos. You can handle this with one LVM volume group consisting of two
>>>> physical volumes. Then you can decide on a per-logical-volume basis
>>>> where it should allocate space and also migrate LVs between the two PVs.
>>>
>>> Since I've got four disks for the pool, I was thinking raid10 with lvm
>>> on top, and a single lvm pv above that.
>>>
>>
>> Yeah, that would also be my recommendation. But if storage efficiency is
>> more relevant, RAID-5 with 4 disks brings you 750GB more usable storage.
>>
>>
> 
> It looks like I'll want to try two different configurations. RAID5 and
> RAID10. Not for different storage requirements, but I want to see
> exactly what the performance drop is.
> 
> I wish lvm striping supported data redundancy. But, then, I wish btrfs
> was ready...
> 

Just out of curiosity: What happens if you do `lvcreate --mirrors 1
--stripes 2 ...`? Does it create something similar to a RAID-10 or does
it simply fail?

Regards,
Florian Philipp


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