Re: LVM over RAID, or plain disks? A:"Yes" = best of both worlds?

[hansbkk@gmail.com]

On Tue, Nov 30, 2010 at 7:42 AM, Neil Brown <neilb@suse.de> wrote:
> If you are comparing recovering after some sort of problem with
> a RAID10 over 6 devices compared with  LVM over 2 2-device RAID1s, then the
> former is certainly easier.  This is simply because there are less layers of
> complexity where something could go wrong.
>
> In both cases, your data will be spread across multiple disks, and any one
> disk or even any two disks would be of no use to you.


Thanks Neil.

Still true with LVM on top of the 6-drive set in either case?


Scenario being
 All the drives are together and OK (generic SATA2, cleanly
disconnected) - but everything else is gone
 Not practical to rebuild the whole set of hosts, just want to get at key data
 Mount the disks on a new machine, boot from SystemRescueCD or Knoppix
 and copy the key data off.


And between RAID6 and RAID10?


> On Mon, 29 Nov 2010 23:00:19 +0700 hansbkk@gmail.com wrote:
>
>> 2010/11/29 Keld Jørn Simonsen <keld@keldix.com>:
>> >> I can see how RAID6 is simpler than RAID10, but compared to RAID1?
>> >
>> > Hmm, does not compute by me. RAID1 and RAID10 are the same in complexity,
>> > RAID10 is just a modern RAID1, and should actually have been called
>> > RAID1.
>>
>> My understanding is that if I use RAID10 on a single pair of disks
>> then that is literally the same as RAID1. These to me are very simple
>> in that I can take either one of the pair and mount it on any normal
>> machine and get at the data without doing anything special.
>>
>> However, if I have my six disks configured as a single RAID10 array, I
>> believe this is no longer true - the data from (at least the larger
>> of) the files has been distributed over all six disks, correct?
>>
>> Now compare putting LVM on top of this array, compared to three RAID1
>> pairs on the one hand and a RAID6 array on the other (third) hand :)
>>
>> If I were trying to recover the data using the latest version of a
>> LiveCD - say Fedora or Knoppix, which would be easier?
>>
>> I'm not trying to score any points, it's a genuine question.
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