Re: Different sized disks for RAID1+0 or RAID10.

[Bill Davidsen <davidsen@tmr.com>]

Kelly Byrd wrote:
>
> On Thu, 11 Oct 2007 11:38:04 -0400, Bill Davidsen <davidsen@tmr.com> wrote:
>   
>> Kelly Byrd wrote:
>>     
>>> I've currently got a pair of identical drives in a RAID1 set for
>>> my data partition. I'll be getting a pair of bigger drives in a
>>> bit, and I was wondering if I could RAID1 those (of course) and
>>> then RAID0 the two differently sized mds. Even better, will RAID10
>>> let me do this?
>>>
>>>       
>> RAID-10 will let you do this, read past threads of this list for
>> discussion of using the "far" option to gain performance.
>>     
>>> I don't need to grow the current RAID1 into this new beast, I've
>>> got a place I can copy the existing data so I can start from
>>> scratch.
>>>
>>>       
>
> Doesn't the 'far' option trade write performance to gain read
> performance? This is a desktop, not at all a "mostly read" type
> workload. 
>
>   
Is your load not read-mostly? The things I want to have happen quickly 
are things like boot, start application, load a document, saved page, or 
man page, compile a kernel (that may not be typical), play an mp3 or 
video, load image(s) in gimp or similar, read mail... all things which 
feel faster if you favor read performance.

I think of it this way: most of the stuff I write is buffered by the 
system and I don't have to wait for it (unless it's huge). Most of the 
large stuff I read, as noted above, is stuff I wait for.

If you look at the times you have to wait for i/o, I bet you will decide 
a desktop is read-mostly after all.
>   
>>> I imagine the answer is: "sure RAID10 / RAID0 let's you do this,
>>> but you don't get the striping performance benefit" for some of
>>> the data", which would be ok with me until the smaller drives go
>>> bad and I replace them.
>>>
>>>       
>> Replacing the smaller drives could be an adventure if you plan to go to
>> larger replacement drives. I don't recall the issues involved with using
>> larger partitions and RAID-10, there's another issue for you to research.
>>
>>     
>
> Will do.
>
>
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>   


-- 
bill davidsen <davidsen@tmr.com>
  CTO TMR Associates, Inc
  Doing interesting things with small computers since 1979