Re: Raid 10 chunksize

On Wed, Apr 1, 2009 at 4:15 PM, Scott Carey <scott@richrelevance.com> wrote:
>
> On 4/1/09 9:54 AM, "Scott Marlowe" <scott.marlowe@gmail.com> wrote:
>
>> On Wed, Apr 1, 2009 at 10:48 AM, Stef Telford <stef@ummon.com> wrote:
>>> Scott Marlowe wrote:
>>>> On Wed, Apr 1, 2009 at 10:15 AM, Stef Telford <stef@ummon.com> wrote:
>>>>
>>>>>     I do agree that the benefit is probably from write-caching, but I
>>>>> think that this is a 'win' as long as you have a UPS or BBU adaptor,
>>>>> and really, in a prod environment, not having a UPS is .. well. Crazy ?
>>>>>
>>>>
>>>> You do know that UPSes can fail, right?  En masse sometimes even.
>>>>
>>> Hello Scott,
>>>    Well, the only time the UPS has failed in my memory, was during the
>>> great Eastern Seaboard power outage of 2003. Lots of fond memories
>>> running around Toronto with a gas can looking for oil for generator
>>> power. This said though, anything could happen, the co-lo could be taken
>>> out by a meteor and then sync on or off makes no difference.
>>
>> Meteor strike is far less likely than a power surge taking out a UPS.
>> I saw a whole data center go black when a power conditioner blew out,
>> taking out the other three power conditioners, both industrial UPSes
>> and the switch for the diesel generator.  And I have friends who have
>> seen the same type of thing before as well.  The data is the most
>> expensive part of any server.
>>
> Yeah, well I¹ve had a RAID card die, which broke its Battery backed cache.
> They¹re all unsafe, technically.

That's why you use two controllers with mirror sets across them and
them RAID-0 across the top.  But I know what you mean.  Now the mobo
and memory are the single point of failure.  Next stop, sequent etc.

> In fact, not only are battery backed caches unsafe, but hard drives.  They
> can return bad data.  So if you want to be really safe:
>
> 1: don't use Linux -- you have to use something with full data and metadata
> checksums like ZFS or very expensive proprietary file systems.

You'd better be running them on sequent or Sysplex mainframe type hardware.

> 4: keep a live redundant system with a PITR backup at another site that can
> recover in a short period of time.
> 3: Run in a datacenter well underground with a plutonium nuclear power
> supply.  Meteor strikes and Nuclear holocaust, beware!

Pleaze, such hyperbole!  Everyone know it can run on uranium just as
well.  I'm sure these guys:
http://royal.pingdom.com/2008/11/14/the-worlds-most-super-designed-data-center-fit-for-a-james-bond-villain/
can sort that out for you.