- info about dm

- info about dm

[Vega Forneris]

Dear all,

I just installed Scientific Linux 5 and I used for the first time DM
drivers for working with the embedded RAID (the servers are IBM xSeries,
with an Adaptec HostRAID ASR - SATA). I really appreciate the fact that
now Linux is able to recognize such devices, but I had some troubles
configuring it and I’d like to have some info for better understanding
how things work. 

I’ll be a little “verbose” for clarifying what I did and which are my
doubts…

1) Installation & Configuration
I installed SL5 on a system which was running SL3 with HW drivers
released by IBM. Linux was able to identify correctly the device
(installed through CD), mapped it as /dev/mapper/asr_ and proceeded with
he installation.

Anyway, I found a little problematic configuring it manually: I tried to
install SL5 on a node which was misconfigured: instead of seeing one
device, it was managing the 2 HD (/dev/sda and /dev/sdb) as 2 separate
devices an if I tried to configure them (at install time, via CD or
network boot) with  DM, I got many errors about the RAID table (“ERROR:
asr: Invalid RAID config table checksum on /dev/sda” or even “asr:
Invalid magic number in RAID table; saw 0x0 expected…”). I tried to
reconfigure the RAID card first via BIOS and then trying again to
configure it via Linux (“dmsetup create …”) but even if it seemed
working (exit code 0), then querying the device asr_ (i.e. “dmraid –r”)
resulted in errors as reported above…or better, dmraid commands (-r,
-ay, -tay,…) reported errors, while dmsetup commands  (status, ls,…)
worked normally. The only way I found for well-configuring the device
was to install SL3 with specific drivers, and then to install SL5 with
DM…both commands now work perfectly

In brief:

If I try to configure DM-RAID from scratch and I get such errors, how
can I do? What’s that “RAID table”? Where is it written? Not in the MBR
of an HD, ‘cause I tried to copy the MBR of the cloned disk which had no
problem (still recognized as “good” for RAID and DM) and nothing
changed…

2) Managing disks
I configured disks in RAID 1 (mirror) but I wonder how to manage this
RAID; in particular, how can I do for:
 - stopping a device (disk) and put it offline/and viceversa? 
 - reconfiguring/rebuilding it (due to broken/faulting HD)? 

At the moment I should change a couple of disks (SMARTD warnings
reported), but I’m scared about the “RAID table error”…

Many Thanks in advance for all help you can give me…

Best Regards
Vega Forneris

+--------------------------------------+
 Vega Forneris

 CNR – Servizi Informatici di Campo
 Gestione servizi GRID

 Area di Ricerca Roma II - Tor Vergata
 Via del Fosso del Cavaliere, 100
 00133 Roma

 Tel:   +39 06 4993 4667
 Fax:   +39 06 4993 4650
 Email: Vega.Forneris@sic.rm.cnr.it
+--------------------------------------+

Re: [dm-devel] - info about dm

[Luca Berra]

Vega,
you should probably address dmraid related question to the ataraid
mailing list.
i am cc-ing the mentioned list, and doing a full quote for that reason


On Wed, Nov 07, 2007 at 02:51:52PM +0100, Vega Forneris wrote:
>Dear all,
>
>I just installed Scientific Linux 5 and I used for the first time DM
>drivers for working with the embedded RAID (the servers are IBM xSeries,
>with an Adaptec HostRAID ASR - SATA). I really appreciate the fact that
>now Linux is able to recognize such devices, but I had some troubles
>configuring it and I’d like to have some info for better understanding
>how things work. 
>
>I’ll be a little “verbose” for clarifying what I did and which are my
>doubts…
>
>1) Installation & Configuration
>I installed SL5 on a system which was running SL3 with HW drivers
>released by IBM. Linux was able to identify correctly the device
>(installed through CD), mapped it as /dev/mapper/asr_ and proceeded with
>he installation.
>
>Anyway, I found a little problematic configuring it manually: I tried to
>install SL5 on a node which was misconfigured: instead of seeing one
>device, it was managing the 2 HD (/dev/sda and /dev/sdb) as 2 separate
>devices an if I tried to configure them (at install time, via CD or
>network boot) with  DM, I got many errors about the RAID table (“ERROR:
>asr: Invalid RAID config table checksum on /dev/sda” or even “asr:
>Invalid magic number in RAID table; saw 0x0 expected…”). I tried to
>reconfigure the RAID card first via BIOS and then trying again to
>configure it via Linux (“dmsetup create …”) but even if it seemed
>working (exit code 0), then querying the device asr_ (i.e. “dmraid –r”)
>resulted in errors as reported above…or better, dmraid commands (-r,
>-ay, -tay,…) reported errors, while dmsetup commands  (status, ls,…)
>worked normally. The only way I found for well-configuring the device
>was to install SL3 with specific drivers, and then to install SL5 with
>DM…both commands now work perfectly
>
>In brief:
>
>If I try to configure DM-RAID from scratch and I get such errors, how
>can I do? What’s that “RAID table”? Where is it written? Not in the MBR
>of an HD, ‘cause I tried to copy the MBR of the cloned disk which had no
>problem (still recognized as “good” for RAID and DM) and nothing
>changed…
>
>2) Managing disks
>I configured disks in RAID 1 (mirror) but I wonder how to manage this
>RAID; in particular, how can I do for:
> - stopping a device (disk) and put it offline/and viceversa? 
> - reconfiguring/rebuilding it (due to broken/faulting HD)? 
>
>At the moment I should change a couple of disks (SMARTD warnings
>reported), but I’m scared about the “RAID table error”…
>
>Many Thanks in advance for all help you can give me…
>
>Best Regards
>Vega Forneris
>
>+--------------------------------------+
> Vega Forneris
>
> CNR – Servizi Informatici di Campo
> Gestione servizi GRID
>
> Area di Ricerca Roma II - Tor Vergata
> Via del Fosso del Cavaliere, 100
> 00133 Roma
>
> Tel:   +39 06 4993 4667
> Fax:   +39 06 4993 4650
> Email: Vega.Forneris@sic.rm.cnr.it
>+--------------------------------------+
>
>
>
>--
>dm-devel mailing list
>dm-devel@redhat.com
>https://www.redhat.com/mailman/listinfo/dm-devel

-- 
Luca Berra -- bluca@comedia.it
        Communication Media & Services S.r.l.
 /"\
 \ /     ASCII RIBBON CAMPAIGN
  X        AGAINST HTML MAIL
 / \

Re: - info about dm

[Phillip Susi]

Luca Berra wrote:
>> Anyway, I found a little problematic configuring it manually: I tried to
>> install SL5 on a node which was misconfigured: instead of seeing one
>> device, it was managing the 2 HD (/dev/sda and /dev/sdb) as 2 separate

This is as expected.  The hardware is just a sata controller with two 
disks attached, so that is what the kernel sees.  dmraid is used to 
recognize the bios information on the disk and configure the device 
mapper driver to create a raid virtual device.

>> devices an if I tried to configure them (at install time, via CD or
>> network boot) with  DM, I got many errors about the RAID table (“ERROR:
>> asr: Invalid RAID config table checksum on /dev/sda” or even “asr:
>> Invalid magic number in RAID table; saw 0x0 expected…”). I tried to
>> reconfigure the RAID card first via BIOS and then trying again to
>> configure it via Linux (“dmsetup create …”) but even if it seemed

dmsetup create creates a new dm device.  Generally this command is for 
debugging and testing, so you should not use it.  It has nothing to do 
with dmraid other than they are both clients of the device mapper kernel 
driver.

>> working (exit code 0), then querying the device asr_ (i.e. “dmraid –r”)
>> resulted in errors as reported above…or better, dmraid commands (-r,
>> -ay, -tay,…) reported errors, while dmsetup commands  (status, ls,…)

What where the exact commands and errors the generated?

I am also confused because the first thing you said was that the system 
DID correctly recognize the raid array as /dev/mapper/asr_xxxx.

>> 2) Managing disks
>> I configured disks in RAID 1 (mirror) but I wonder how to manage this
>> RAID; in particular, how can I do for:
>> - stopping a device (disk) and put it offline/and viceversa? - 
>> reconfiguring/rebuilding it (due to broken/faulting HD)?
>> At the moment I should change a couple of disks (SMARTD warnings
>> reported), but I’m scared about the “RAID table error”…

Currently the only way is to do so in the bios.  Some systems the bios 
will begin rebuilding when you tell it to, and you need to wait for it 
to finish.  On others, it only marks the disk as needing rebuilt and 
relies on the windows driver to do the rebuilding.  Currently dmraid 
does not perform rebuilding.

R: - info about dm

[Vega Forneris]

Dear Philip, Sean and all,

First of all I apologize for what I wrote: I recognize that's not
clear...

However at the moment I cannot reproduce the error because I solved the
issue through a workaround and I (stupid) didn't save any log of that.

Instead of trying to explain better what I wrote (in a mess!!!), can you
explain how to work with dmraid? Is there any official HowTo?
Man pages don't give us a step by step procedure and that's what I need
now

Some info about the machines:
HW: IBM x306 - 2 HD 160GB SATA - Adaptec HostRAID ASR (onboard)

# dmraid -tay
cl->raidtype=1 rd_type=64
cl->raidtype=1 rd_type=64
cl->raidtype=1 rd_type=64
cl->raidtype=1 rd_type=64
asr_: 0 312580096 mirror core 2 131072 nosync 2 /dev/sda 0 /dev/sdb 0
asr_1: 0 71681967 linear /dev/mapper/asr_ 63
asr_2: 0 4096575 linear /dev/mapper/asr_ 71682030
asr_3: 0 236798100 linear /dev/mapper/asr_ 75778605

# dmraid -r
cl->raidtype=1 rd_type=64
cl->raidtype=1 rd_type=64
/dev/sda: asr, "asr_", mirror, ok, 312580096 sectors, data@ 0
/dev/sdb: asr, "asr_", mirror, ok, 312580096 sectors, data@ 0

# dmsetup status
asr_p1: 0 71681967 linear 
asr_: 0 312580096 mirror 2 8:0 8:16 2385/2385 1 AA 1 core
asr_p3: 0 236798100 linear 
asr_p2: 0 4096575 linear 

# dmsetup ls
asr_p1  (253, 1)
asr_    (253, 0)
asr_p3  (253, 3)
asr_p2  (253, 2)

Let's handle a couple of doubts I have:

1) I need to change an HD which has problems...here the steps I guess
from what I read in these days:
- halt the machine (ok, ok it's obvious ;-P )
- change the faulty HD
- boot
- when BIOS starts the RAID manager, enter and rebuild the RAID (1:
mirror)
- after the rebuilding, everything should be ok.

...is it correct?

2) I have a machine with 2 HD SATA, on the first we have the OS
installed (and working!), the second is blank (just added), I want to
create a RAID 1 (mirror) of the whole disk:
- ...
I don't want to guess ;-P

I know how to manage grub for booting from the new device, but I'm not
sure how to create such device...

Any tip is welcome!

Cheers and thanks
Vega

-----Messaggio originale-----
Da: dm-devel-bounces@redhat.com [mailto:dm-devel-bounces@redhat.com] Per
conto di Phillip Susi
Inviato: lunedì 12 novembre 2007 22.16
A: dm-devel@redhat.com; ataraid-list@redhat.com
Oggetto: Re: [dm-devel] - info about dm

Luca Berra wrote:
>> Anyway, I found a little problematic configuring it manually: I tried
to
>> install SL5 on a node which was misconfigured: instead of seeing one
>> device, it was managing the 2 HD (/dev/sda and /dev/sdb) as 2
separate

This is as expected.  The hardware is just a sata controller with two 
disks attached, so that is what the kernel sees.  dmraid is used to 
recognize the bios information on the disk and configure the device 
mapper driver to create a raid virtual device.

>> devices an if I tried to configure them (at install time, via CD or
>> network boot) with  DM, I got many errors about the RAID table
(“ERROR:
>> asr: Invalid RAID config table checksum on /dev/sda” or even “asr:
>> Invalid magic number in RAID table; saw 0x0 expected…”). I tried to
>> reconfigure the RAID card first via BIOS and then trying again to
>> configure it via Linux (“dmsetup create …”) but even if it seemed

dmsetup create creates a new dm device.  Generally this command is for 
debugging and testing, so you should not use it.  It has nothing to do 
with dmraid other than they are both clients of the device mapper kernel

driver.

>> working (exit code 0), then querying the device asr_ (i.e. “dmraid
–r”)
>> resulted in errors as reported above…or better, dmraid commands (-r,
>> -ay, -tay,…) reported errors, while dmsetup commands  (status, ls,…)

What where the exact commands and errors the generated?

I am also confused because the first thing you said was that the system 
DID correctly recognize the raid array as /dev/mapper/asr_xxxx.

>> 2) Managing disks
>> I configured disks in RAID 1 (mirror) but I wonder how to manage this
>> RAID; in particular, how can I do for:
>> - stopping a device (disk) and put it offline/and viceversa? - 
>> reconfiguring/rebuilding it (due to broken/faulting HD)?
>> At the moment I should change a couple of disks (SMARTD warnings
>> reported), but I’m scared about the “RAID table error”…

Currently the only way is to do so in the bios.  Some systems the bios 
will begin rebuilding when you tell it to, and you need to wait for it 
to finish.  On others, it only marks the disk as needing rebuilt and 
relies on the windows driver to do the rebuilding.  Currently dmraid 
does not perform rebuilding.


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Re: R: [dm-devel] - info about dm

[Phillip Susi]

Vega Forneris wrote:
> 1) I need to change an HD which has problems...here the steps I guess
> from what I read in these days:
> - halt the machine (ok, ok it's obvious ;-P )
> - change the faulty HD
> - boot
> - when BIOS starts the RAID manager, enter and rebuild the RAID (1:
> mirror)
> - after the rebuilding, everything should be ok.
> 
> ...is it correct?

Yes... at least if your bios actually starts the rebuild process instead 
of just marking the array as needing rebuilt and relying on the OS to do 
it.

> 2) I have a machine with 2 HD SATA, on the first we have the OS
> installed (and working!), the second is blank (just added), I want to
> create a RAID 1 (mirror) of the whole disk:
> - ...
> I don't want to guess ;-P

The same way you did it the first time: in the bios.  Doing so will 
destroy the existing data on the drive though, so you will want to 
backup first.

R: R: - info about dm

[Vega Forneris]

Hi Phillip,

Thanks for the answer

>> Yes... at least if your bios actually starts the rebuild process
instead 
>> of just marking the array as needing rebuilt and relying on the OS to
do 
>> it.

...well I have to test it: during the installation procedures, when I
tried to configure this damn RAID and I got the disk inconsistency
(“ERROR:
asr: Invalid RAID config table checksum on /dev/sda” or “asr: Invalid
magic number in RAID table; saw 0x0 expected…”) I tested even the
rebuilding through the BIOS with no results, while I'm sure the
rebuilding works (tested with working HD)...bah, maybe the rebuilding
was not completed and I had to wait a little longer...

Can you specify which commands are used for creating the device
(manually) the first time? I used "dmsetup create" but someone replied
that dmsetup is a debug command rather than the correct procedure. 
Let me repeat ("repetita juvant": latin proverb ;-P): DM simply
recognize a BIOS RAID configuration and translate it to the system,
mapping it to a virtual device...so all I need is to launch "dmraid -ay"
for activating...

One last question, about the development: are they working for having a
way to "manage" RAID through DM? I'm talking above all about stopping
the RAID, disabling disks, rebuilding the RAID...

Thanks again for all the support
Vega



-----Messaggio originale-----
Da: dm-devel-bounces@redhat.com [mailto:dm-devel-bounces@redhat.com] Per
conto di Phillip Susi
Inviato: martedì 13 novembre 2007 19.22
A: ATARAID (eg, Promise Fasttrak, Highpoint 370) related discussions
Cc: 'device-mapper development'
Oggetto: Re: R: [dm-devel] - info about dm

Vega Forneris wrote:
> 1) I need to change an HD which has problems...here the steps I guess
> from what I read in these days:
> - halt the machine (ok, ok it's obvious ;-P )
> - change the faulty HD
> - boot
> - when BIOS starts the RAID manager, enter and rebuild the RAID (1:
> mirror)
> - after the rebuilding, everything should be ok.
> 
> ...is it correct?

Yes... at least if your bios actually starts the rebuild process instead

of just marking the array as needing rebuilt and relying on the OS to do

it.

> 2) I have a machine with 2 HD SATA, on the first we have the OS
> installed (and working!), the second is blank (just added), I want to
> create a RAID 1 (mirror) of the whole disk:
> - ...
> I don't want to guess ;-P

The same way you did it the first time: in the bios.  Doing so will 
destroy the existing data on the drive though, so you will want to 
backup first.

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