raidtools vs mdadm

i work for a software company that develops backup and disaster recovery
software for linux. our product supports software raid, but i must say
that we currently only support it when devices are created with
raidtools. i only recently heard about mdadm and am very impressed with
its flexibility and funtionality.

my question is how popular is mdadm in production environments as this
compares to raidtools?

is mdadm used to configure software raid on any distribution
installations?

is mdadm trending to become the defacto standard for software raid on
linux?

rich turner

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RE: raidtools vs mdadm

As I understand it, raidtools is not supported anymore. The gods of RAID
support mdadm. I get this info from this list.

RedHat 9 still uses raidtools. I don't know about the newer versions of
redhat. RedHat, you there? Please use mdadm! I don't know what other
distributions use. I plan to give Debian a try the next time I setup a
system.

People have posted patches to remove raidstart from the startup scripts, and
replace them with mdadm.

I use mdadm, it is much better at starting arrays with issues, and
correcting them. However I still use the stock scripts during re-boot which
still use raidstart.

I think raidtools has 1 item that mdadm does not. That is raidreconf.
Mdadm does not support that function. Correct me if I am wrong!

Guy

-----Original Message-----
From: linux-raid-owner@vger.kernel.org
[mailto:linux-raid-owner@vger.kernel.org] On Behalf Of rich turner
Sent: Tuesday, August 31, 2004 2:56 PM
To: linux-raid@vger.kernel.org
Subject: raidtools vs mdadm

i work for a software company that develops backup and disaster recovery
software for linux. our product supports software raid, but i must say
that we currently only support it when devices are created with
raidtools. i only recently heard about mdadm and am very impressed with
its flexibility and funtionality.

my question is how popular is mdadm in production environments as this
compares to raidtools?

is mdadm used to configure software raid on any distribution
installations?

is mdadm trending to become the defacto standard for software raid on
linux?

rich turner

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RE: raidtools vs mdadm

I currently use a combination of raidtools and mdadm. I may be the
exception rather than the rule because I'm currently using an old
distribution (Red Hat 7.3) because of application compatibility.

I use mdadm exclusively for management of arrays though (failing, hot
removing, hot adding, monitoring). Fedora Core 2 is using mdadm for
monitoring although I'm not sure what FC2 anaconda is using to setup
RAID arrays. I believe it still uses raidtools and rc.sysinit on FC2
still uses raidtools. I'm a RH die-hard so I'm not sure what other
distros use.

I would venture to say that mdadm is becoming the defacto although it's
not quite there yet.

> -----Original Message-----
> From: linux-raid-owner@vger.kernel.org
> [mailto:linux-raid-owner@vger.kernel.org] On Behalf Of rich turner
> Sent: Tuesday, August 31, 2004 2:56 PM
> To: linux-raid@vger.kernel.org
> Subject: raidtools vs mdadm
>
> i work for a software company that develops backup and
> disaster recovery software for linux. our product supports
> software raid, but i must say that we currently only support
> it when devices are created with raidtools. i only recently
> heard about mdadm and am very impressed with its flexibility
> and funtionality.
>
> my question is how popular is mdadm in production
> environments as this compares to raidtools?
>
> is mdadm used to configure software raid on any distribution
> installations?
>
> is mdadm trending to become the defacto standard for software
> raid on linux?
>
> rich turner
>
> -
> To unsubscribe from this list: send the line "unsubscribe
> linux-raid" in the body of a message to
> majordomo@vger.kernel.org More majordomo info at
> http://vger.kernel.org/majordomo-info.html
>
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RE: raidtools vs mdadm

are there any incompatibilities related to mdadm? does it only support
the md driver at a certain level? our software supports kernel version
2.2 and later.

does it fully support creating a raid device on logical volumes, and
creating logical volumes on raid devices? i have played with this a
little and havent seen any problems but i thought i would ask to see if
anyone has seen anything.

would i expect to see the mdadm executable available on most
distributions today by default?

i realize that raid devices created with raidtools and raid devices
created with mdadm can co-exist. is there an easy way to know which
method was used to create them?

thanks for the responses


On Tue, 2004-08-31 at 12:38, Rechenberg, Andrew wrote:
> I currently use a combination of raidtools and mdadm. I may be the
> exception rather than the rule because I'm currently using an old
> distribution (Red Hat 7.3) because of application compatibility.
>
> I use mdadm exclusively for management of arrays though (failing, hot
> removing, hot adding, monitoring). Fedora Core 2 is using mdadm for
> monitoring although I'm not sure what FC2 anaconda is using to setup
> RAID arrays. I believe it still uses raidtools and rc.sysinit on FC2
> still uses raidtools. I'm a RH die-hard so I'm not sure what other
> distros use.
>
> I would venture to say that mdadm is becoming the defacto although it's
> not quite there yet.
>
> > -----Original Message-----
> > From: linux-raid-owner@vger.kernel.org
> > [mailto:linux-raid-owner@vger.kernel.org] On Behalf Of rich turner
> > Sent: Tuesday, August 31, 2004 2:56 PM
> > To: linux-raid@vger.kernel.org
> > Subject: raidtools vs mdadm
> >
> > i work for a software company that develops backup and
> > disaster recovery software for linux. our product supports
> > software raid, but i must say that we currently only support
> > it when devices are created with raidtools. i only recently
> > heard about mdadm and am very impressed with its flexibility
> > and funtionality.
> >
> > my question is how popular is mdadm in production
> > environments as this compares to raidtools?
> >
> > is mdadm used to configure software raid on any distribution
> > installations?
> >
> > is mdadm trending to become the defacto standard for software
> > raid on linux?
> >
> > rich turner
> >
> > -
> > To unsubscribe from this list: send the line "unsubscribe
> > linux-raid" in the body of a message to
> > majordomo@vger.kernel.org More majordomo info at
> > http://vger.kernel.org/majordomo-info.html
> >

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Re: raidtools vs mdadm

On Tuesday August 31, rich@storix.com wrote:
> i work for a software company that develops backup and disaster recovery
> software for linux. our product supports software raid, but i must say
> that we currently only support it when devices are created with
> raidtools. i only recently heard about mdadm and am very impressed with
> its flexibility and funtionality.

Thanks.

>
> my question is how popular is mdadm in production environments as this
> compares to raidtools?

It's hard to say. Quite a few people on this list use it. There are
regularly people appearing who don't know about it. I'd say it's
popularity is steadily growing. I suspect you could help there....


>
> is mdadm used to configure software raid on any distribution
> installations?

I don't know.

>
> is mdadm trending to become the defacto standard for software raid on
> linux?

It is on this list. But the world is much bigger than this list.

NeilBrown
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RE: raidtools vs mdadm

On Tuesday August 31, rich@storix.com wrote:
> are there any incompatibilities related to mdadm? does it only support
> the md driver at a certain level? our software supports kernel version
> 2.2 and later.

mdadm should support everything, though I haven't tested it much on
2.2. The "--assemble" functionality has to be implemented very
differently in 2.2. I don't know how well it works.

>
> does it fully support creating a raid device on logical volumes, and
> creating logical volumes on raid devices? i have played with this a
> little and havent seen any problems but i thought i would ask to see if
> anyone has seen anything.

It creates raid arrays on anything, and the raid arrays can be used
for anything. The arrays created with mdadm are indistinguishable
from arrays created with raidtools.

>
> would i expect to see the mdadm executable available on most
> distributions today by default?

I think so. It depends on what you mean by "default".
On debian, it isn't part of the base distribution, but nor is
raidtools. "apt-get" gets it easily.

>
> i realize that raid devices created with raidtools and raid devices
> created with mdadm can co-exist. is there an easy way to know which
> method was used to create them?

It is impossible to know. There is no difference.

NeilBrown
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RE: raidtools vs mdadm

On Tue, 31 Aug 2004, Guy wrote:

> As I understand it, raidtools is not supported anymore. The gods of RAID
> support mdadm. I get this info from this list.
>
> RedHat 9 still uses raidtools. I don't know about the newer versions of
> redhat. RedHat, you there? Please use mdadm! I don't know what other
> distributions use. I plan to give Debian a try the next time I setup a
> system.

Debian Woody supplies both raidtools and mdadm - it's up to you which
package you install. For the past 5-6 years, I've been using raidtools, as
thats all I've had avalable, so I understand them well and still use them.
However, I'm looking at mdadm for future builds and have just installed it
on one of my servers (which I've already built with raidtools)

Woody can't create RAID sets during install time, but I understand the new
Debian (Sarge) installer is avalable now for testing which does
incorporate this feature.

> People have posted patches to remove raidstart from the startup scripts, and
> replace them with mdadm.

Just don't install raidtools - by the looks of the startup scripts they
are multually exclusive anyway, but I've patched the mdadm-raid startup to
not execute on my local server (not strictly neccessary anyway as I'm
using the auto start (0xFD) feature anyway) This is more or less essential
to boot off RAID1 as far as I can tell.

Gordon
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Re: raidtools vs mdadm

On Tue, Aug 31, 2004 at 11:55:43AM -0700, rich turner wrote:
>i work for a software company that develops backup and disaster recovery
>software for linux. our product supports software raid, but i must say
>that we currently only support it when devices are created with
>raidtools. i only recently heard about mdadm and am very impressed with
>its flexibility and funtionality.
>
>my question is how popular is mdadm in production environments as this
>compares to raidtools?
it is surely gaining popularity, but i don't have any number

>is mdadm used to configure software raid on any distribution
>installations?
mandrakelinux is switching to mdadm for next release.

>is mdadm trending to become the defacto standard for software raid on
>linux?
i would hope so, but then i am biased.

L.


--
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Communication Media & Services S.r.l.
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RE: raidtools vs mdadm

On Tue, 2004-08-31 at 17:54, Neil Brown wrote:
> On Tuesday August 31, rich@storix.com wrote:
>
> > i realize that raid devices created with raidtools and raid devices
> > created with mdadm can co-exist. is there an easy way to know which
> > method was used to create them?
>
> It is impossible to know. There is no difference.
if i were to read the superblock myself, would it look different for
devices created with mdadm than with devices created with raidtools? i
am trying to figure out a way of knowing which tool was used to create
them in the event that we need to rebuild them. any difference i can
count on consistently is what i am looking for. the problem is that if
we recreate raid devices using mdadm and their init scripts dont start
the raid devices then the devices will not be assembled, and could
possibly cause the system to not boot.
>
> NeilBrown

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RE: raidtools vs mdadm

On Wednesday September 8, rich@storix.com wrote:
> On Tue, 2004-08-31 at 17:54, Neil Brown wrote:
> > On Tuesday August 31, rich@storix.com wrote:
> >
> > > i realize that raid devices created with raidtools and raid devices
> > > created with mdadm can co-exist. is there an easy way to know which
> > > method was used to create them?
> >
> > It is impossible to know. There is no difference.
> if i were to read the superblock myself, would it look different for
> devices created with mdadm than with devices created with raidtools?

No. There is no different. Zero. They are the same thing.

> i
> am trying to figure out a way of knowing which tool was used to create
> them in the event that we need to rebuild them. any difference i can
> count on consistently is what i am looking for. the problem is that if
> we recreate raid devices using mdadm and their init scripts dont start
> the raid devices then the devices will not be assembled, and could
> possibly cause the system to not boot.

How you create the array and how you start the array are two different
things. They don't need to be done with the same tool.

If the init scripts don't start an array created with mdadm, then they
won't start an array created with raidtools either.

NeilBrown
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RE: raidtools vs mdadm

On Wed, 2004-09-08 at 19:42, Neil Brown wrote:
> On Wednesday September 8, rich@storix.com wrote:
> > On Tue, 2004-08-31 at 17:54, Neil Brown wrote:
> > > On Tuesday August 31, rich@storix.com wrote:
> > >
> > > > i realize that raid devices created with raidtools and raid devices
> > > > created with mdadm can co-exist. is there an easy way to know which
> > > > method was used to create them?
> > >
> > > It is impossible to know. There is no difference.
> > if i were to read the superblock myself, would it look different for
> > devices created with mdadm than with devices created with raidtools?
>
> No. There is no different. Zero. They are the same thing.
>
> > i
> > am trying to figure out a way of knowing which tool was used to create
> > them in the event that we need to rebuild them. any difference i can
> > count on consistently is what i am looking for. the problem is that if
> > we recreate raid devices using mdadm and their init scripts dont start
> > the raid devices then the devices will not be assembled, and could
> > possibly cause the system to not boot.
>
> How you create the array and how you start the array are two different
> things. They don't need to be done with the same tool.
>
> If the init scripts don't start an array created with mdadm, then they
> won't start an array created with raidtools either.

Actually, some initscripts (I'm familiar with FC2) do a sanity check for
the existence of configuration files. I created my array with mdadm but
didn't bother to set up /etc/raidtab. the absence of /etc/raidtab as a
file caused the initscripts (rc.sysinit) to skip trying to start the
raid.

Once I modified rc.sysint to test for /etc/mdadm.conf and use mdadm
--assemble --scan, everything worked fine.

Mileage varies depending on how the initscript was written. and how you
have provided configuration details.

>
> NeilBrown
> -
--
------------------------------
Bob Hillegas
bobhillegas@houston.rr.com

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