[Beowulf] hardware RAID versus mdadm versus LVM-striping

Richard Chang rchang.lists at gmail.com
Tue Jan 19 11:44:59 EST 2010

Joe Landman wrote:
> Hi Richard:
>   This I cannot tell you, as I don't have a comprehensive list of what 
> uses what driver.  I'd suggest looking at what drivers it loads for 
> disks when it comes up.  If dmraid comes up *and* enumerates devices, 
> you have a strong probability that it is a fake-raid.  This is not to 
> say dmraid is bad.  Again, its the underlying driver or chipset that 
> we often run into problems with.
Thanks Joe,

This is a much better picture. I am sure there is no such thing as 
"dmraid" coming up when the system I maintain, starts.
> Rarely.  Fake raid will generally not have any RAM cache or battery 
> backup capability.

I am also sure, all the storage controllers that I have mentioned have a 
Battery and RAM Cache.

> In some instances, fake raid is *ok* for OS drives (RAID1 only), if 
> the bios is smart enough to use it correctly, the underlying fake raid 
> driver is relatively stable, and you have reasonable disks.  
> Otherwise, mdadm works great, though you have to patch Redhat/Centos, 
> as they, by default, use dmraid for the moment.  Later model Fedora 
> appear to have switched to MD raid (after 9 from what I saw, last time 
> I played with it).

I really appreciate your effort and the time taken to reply back.


Beowulf mailing list, Beowulf at beowulf.org sponsored by Penguin Computing
To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf

More information about the Beowulf mailing list