[CentOS] Re: A question about RAID and partitions

Tue May 22 22:56:51 UTC 2007
Les Mikesell <lesmikesell at gmail.com>

Miguel Medalha wrote:
>> have raid 0 and raid1 on the same drive isn't going to gie you anything
>> since the raid 1 will "slow" the other raids down.
> You are assuming that both arrays will always be concurrently accessed 
> but that may not be the case.
> More yet: the configuration may have been studied in such a way that 
> concurrent access is rarely the case.

If you only have 2 drives there's not much you can do to avoid 
concurrent access.  The killer is head seek time - if you have your only 
2 drives tied together in any kind of raid and the head needs to be in 2 
places at once it doesn't matter much how you laid out the partitions. 
Reads can be sort-of independent on raid1 but writes make both seek to 
the same place.

   Les Mikesell
    lesmikesell at gmail.com