[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 7/1/20 7:04 AM, Reco wrote:


On Wed, Jul 01, 2020 at 08:49:09PM +1000, elvis wrote:

On 1/7/20 4:51 am, Dan Ritter wrote:

Miles Fidelman wrote:

On 6/29/20 7:20 PM, Dan Ritter wrote:


Miles Fidelman wrote:

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


Miles Fidelman wrote:

Now who's being pedantic?

Precisely.


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

And it's OK to refer to the whole thing as an mdadm RAID.

No.. if you want to be pedantic, the proper terminology is "Linux Raid" or
"md RAID."?? mdadm is one of several admin programs available

What are the others, please? (That will work on a modern system,
say, Debian stable or oldstable or unstable.)

I think there's precisely one -- libblockdev2.

lvm does its own raid now too...

https://www.reddit.com/r/linuxquestions/comments/9kkk3b/md_raid_lvm_vs_lvm_raid/

... and it's not the mdraid, but entirely different kernel subsystem.
Last time I've checked it, they did not even implemented incremental
RAID assembly in LVM, meaning that you won't be able to use such array
if a single drive from LVM-based RAID will fail.
They've solved this problem in mdraid like 15 years ago.


But staying on-topic, I'm too very interested to hear about alternative
interfaces to mdraid, which do not involve mdadm. libblockdev2 does not
count, it's merely a wrapper.
Sure looks like LVM raid make use of the same underlying md raid software as administered mdadm.
Which kind of just reiterates what I said earlier - mdadm, as an administrative interface, is distinct & separate from the various software components that create md raid devices.  In the past, there were several other admin programs, but mdadm seems to be the major, maintained tool.
The info that LVM now includes some direct raid setup tools (that also make use of the underlying mdraid system), is new, and possibly useful.
Which does raise an interesting question:  When the Debian installer gives the option to set up RAID volumes, does it use mdadm, or do it's own config, or use common libraries?  (Kind of arcane, but inquiring minds want to know.) 

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: