[Beowulf] hardware RAID versus mdadm versus LVM-striping
rchang.lists at gmail.com
Tue Jan 19 08:44:59 PST 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.
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.
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