[geeks] RAID0+1 and ideas, etc...

[Nick B]

I should mention FusionIO's suggested solution for truly critical data is
redundant servers, with one (or more) fusionio card in each.
Nick


On Thu, Nov 7, 2013 at 11:55 AM, Nick B <nick at pelagiris.org> wrote:

> Fusionio says "Don't mirror our cards, it's dumb", and in most cases they
> are right.  Fairly frequently trying to mirror fusionio cards will result
> in a significant performance drop, and they are pretty darn reliable.  Is
> your use case so critical that the faint chance of data loss is a killer,
> while the likely loss of performance is acceptable?  (then why do you have
> fusionio cards?)
>
> Man that was worthless.  I suspect the customer has spent a lot of money
> on that third fusionio card, which will buy them next to nothing, but their
> approach will work fine for what it is.
> Nick
>
>
> On Thu, Nov 7, 2013 at 11:29 AM, Sandwich Maker <adh at an.bradford.ma.us>wrote:
>
>> " From: Jonathan Katz <jon at jonworld.com>
>> "
>> " All,
>> "
>> " Say you're running a Linux server. It has six Fusion IO cards, each
>> " presents two disk devices giving you a total of 12 disk devices. You
>> " want to RAID 1+0 this setup so that if any physical card or disk
>> " device dies, you're still operational.
>> "
>> " My customer set this up using mdraid to stripe the two disk devices
>> " within the individual cards. So we go from 12 disk devices to six md
>> " stripes. Then the md stripes are mirrored card-by-card (so there are 3
>> " md mirror/RAID1 devices.) Then LVM is used to stripe the three
>> " remaining cards into one large volume that we use.
>> "
>> " I'm not sure this is the best way to do it, and I want to hear from
>> " others who deal with this what they think (which is why I'm throwing
>> " this out there.) The requirement is for one decent sized, reliable
>> " storage pool of data. I think we have an extra layer of abstraction
>> " here, but I'm not sure how to redo this, or if we even should.
>> "
>> " What say the mind trust?
>>
>> what disksuite does in that situation is
>> a. mirror the drive pairs on each card
>> b. stripe the 6 mirrors
>> thus allowing you to survive any combination of 1-disk-per-card
>> failures.  it does this even if you try to configure 2 stripes and
>> mirror them, and it makes sense - with mirrored stripes, one failure
>> on each side would take you down.
>>
>> i would mirror first, then lvm the mirrors.  it would make sense to
>> mirror pairs across cards, to provide card-failure hardness.
>> ________________________________________________________________________
>> Andrew Hay                                  the genius nature
>> internet rambler                            is to see what all have seen
>> adh at an.bradford.ma.us                       and think what none thought
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