RAID5 gets a bad rap

[Gordon Messmer]

Bill Davidsen wrote:
> Gordon Messmer wrote:
>> Your assertion ignores the fact that filesystems themselves are, in 
>> fact, databases.  Real-world experience with many production systems 
>> and many workloads has convinced me to use RAID 5 as rarely as 
>> possible. Even when I'm forced to use it, I generally choose a RAID 
>> 5+0 configuration as I get much better performance.
>>
> Or you might want to read the man pages for md and mdadm. RAID10 is 
> faster (assuming you use the "far 2" config). No, RAID10 is not another 
> name for RAID1+0...


When I read the man page for "md", I see:

    RAID10
        RAID10  provides  a combination of RAID1 and RAID0, and is
        sometimes known as RAID1+0.

...so I'm not sure what man page you've been reading.

I know that RAID 10 is faster than RAID 5+0.  I meant that in the rare 
circumstance when I'm trying to build a very large volume of disks (say, 
20), I'll usually create four RAID5 arrays with five disks each, and 
then stripe them.  The resulting array (RAID 5+0) will be more resilient 
to failure and perform much better than a single RAID5 array containing 
all 20 disks.