[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Re: Advice on hardware server to use for small a dedicated data center

On 6/29/20 9:10 AM, Dan Ritter wrote:

Miles Fidelman wrote:
Just to be clear... mdadm is NOT raid - it's an admin program for managing
linux raid (md) devices.?? And then you need to worry about LVM (logical
volume manager), and a network file system on top of them.
Just to be clear, you are being pedantic bordering on wrong here. This
is like saying "a hamburger is not ground beef patties, and then you
need to worry about vegetables and condiments".

mdadm is the administrative interface program for the kernel's md
subsystem. It is used generically as a synonym for "the kernel's
md subsystem" because for most people encountering them, they
are inextricably intertwined.

The kernel's md subsystem manages RAID 0, 1, 4, 5, 6 and 10. It
also has a non-RAID linear mode, a container abstraction, and a
fault-simulation mode.

Now who's being pedantic?

And isn't this exactly what I said?  mdadm is an admin program, it doesn't perform the raid function.

LVM is completely independent of the md subsystem, and can be
used with or without it. Some people love it. Some avoid it like
the plague -- oops. Some avoid it like rational people avoid the

Various network file systems are also completely independent of
the md subsystem.
ZFS is an integrated data storage system that presents N
filesystem and partition-equivalent views to the kernel. It is
independent of and an alternative to md and lvm. It offers a
semi-integrated NFS and CIFS export facility. Underneath, it
offers storage options including error-detection, compression, mirroring,
striping, RAID-5 and -6 style parity, read caching and write
caching. Only the error detection is mandatory.

I'm pretty sure we all know this.  The point is that comparing mdadm to ZFS is an apples to oranges comparison.  You don't chose between mdadm and ZFS, you chose between ZFS and a stack of software that performs the same set of functions.

Miles Fidelman

In theory, there is no difference between theory and practice.
In practice, there is.  .... Yogi Berra

Theory is when you know everything but nothing works.
Practice is when everything works but no one knows why.
In our lab, theory and practice are combined:
nothing works and no one knows why.  ... unknown

Reply to: