RSYNC Fedora (Moving onto RAID...)

[William Hooper]

Scott Burns  said:
> William Hooper wrote:
>
>>
>>Of course if both disks of a mirror set die you lose everything, too.
>>
>>
>>
> Yes.
>
> The guy was recommending RAID10 ( a bunch of RAID1 pairs then add them
> all together as RAID0 ).
>
> After reading it I worked out a number comparing a RAID5 with 5 disks
> against RAID10 with 4 stripped sets of 3 disks (12 in total ).  If you
> lose 2/5 RAID5 disks you are all lost.

Apples and oranges.  If you are going to compare multiple sets, why not
compare 4 RAID5 sets w/ 3 disks each (12 in total).

>  If you lose 5/12 RAID10s you
> still have over a 95% chance of no data lost.  I believe recovery time
> on RAID10 puts RAID5 to shame too.  His entire rant can be found at
> http://groups.google.com.au/groups?q=quarterly+raid+5+rant+group:comp.databases.informix&hl=en&lr=&ie=UTF-8&group=comp.databases.informix&selm=pan.2003.07.31.16.49.22.318281.15473%40bloomberg.net&rnum=5
>

He answers your question there:
"Well with RAID10 there is no danger unless the one mirror that is
recovering also fails and that's 80% or more less likely than that any
other drive in a RAID5 array will fail!"

Of course, he falls into the same trap you did, comparing a single RAID5
set with multiple RAID10 sets.

-- 
William Hooper