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Old 11-18-2008, 04:34 PM
 
Default CentOS 5.2 with IBM SERVERAID 6i

I need to install CentOS 5.2 on a IBM Server xSeries 226, which comes
with a IBM SERVERAID 6i RAID card. I think it is not a true hardware
RAID card. I has, nevertheless, an interesting feature: 128MB of cache
with battery backup.


I launched the CentOS boot DVD and CentOS correctly identified the
card and the RAID 5 array as configured by the controller's BIOS.


My question now is: what would be the better way to implement RAID 5
on this server? Should I use the detected array and respective driver
or should I delete the array and go for Linus Software RAID?


If both solutions are in fact Software RAID, is there any particular
reason to prefer one of the methods?


I know that Linux RAID will create a universal, more compatible array,
readable on any Linux machine. But is there some other reason that
makes it preferrable to use the SERVERAID driver provided by CentOS?
Is it optimized in any way that recommends its use?


Will the controller still make use of its cache and battery backup if
configured as a plain SCSI controller with Linux Software RAID?


I hope that some more experienced list member can ellucidate me on this.

Thank you!

PS - The machine is powered by a Intel P4 Xeon processor served by
2.5GB of RAM. The disks are 3 IBM 10K rpm SCSI 320 with 73 GB each.

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Old 11-18-2008, 04:51 PM
Jim Wildman
 
Default CentOS 5.2 with IBM SERVERAID 6i

On Tue, 18 Nov 2008, miguelmedalha@sapo.pt wrote:

My question now is: what would be the better way to implement RAID 5 on this
server? Should I use the detected array and respective driver or should I
delete the array and go for Linus Software RAID?




I don't know about throughput, but using software RAID has the following
plus'es (in my book)
1) no need for the vendor specific agents to monitor
2) if/when you get larger drives, you can sub them into the array and
then expand it. I haven't seen a hardware RAID card yet that will allow
that


----------------------------------------------------------------------
Jim Wildman, CISSP, RHCE jim@rossberry.com http://www.rossberry.com
"Society in every state is a blessing, but Government, even in its best
state, is a necessary evil; in its worst state, an intolerable one."
Thomas Paine
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Old 11-18-2008, 05:04 PM
"nate"
 
Default CentOS 5.2 with IBM SERVERAID 6i

miguelmedalha@sapo.pt wrote:

> I know that Linux RAID will create a universal, more compatible array,
> readable on any Linux machine. But is there some other reason that
> makes it preferrable to use the SERVERAID driver provided by CentOS?
> Is it optimized in any way that recommends its use?

I always prefer hardware raid over software raid primarily for
hot swap purposes, if a drive is dead I just yank it, replace it
and don't have to worry about it, rebuild is automatic. This may
be the case with linux software raid now I'm not sure, a few years
ago hot swap was somewhat iffy and results varied widely on the
controller(e.g. could panic/hang the box in some situations).

Also root on raid is much simpler with hardware raid than software
raid. If you have battery backed cache as yours appears to have,
you have the added advantage of write back caching which can
give higher performance.

Out of the 400 or so raid cards I've used over the years I recall
only 2, maybe 3 of them having trouble(failing/faulty).

So in short I always prefer hardware raid because it is simpler
to operate for me at least. That is provided it is a true
hardware raid controller, there are a lot of shit hybrid
software/hardware raid cards out there, I do not trust them.

nate

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Old 11-18-2008, 05:09 PM
Chris Geldenhuis
 
Default CentOS 5.2 with IBM SERVERAID 6i

miguelmedalha@sapo.pt wrote:
I need to install CentOS 5.2 on a IBM Server xSeries 226, which comes
with a IBM SERVERAID 6i RAID card. I think it is not a true hardware
RAID card. I has, nevertheless, an interesting feature: 128MB of cache
with battery backup.


I launched the CentOS boot DVD and CentOS correctly identified the
card and the RAID 5 array as configured by the controller's BIOS.


My question now is: what would be the better way to implement RAID 5
on this server? Should I use the detected array and respective driver
or should I delete the array and go for Linus Software RAID?


If both solutions are in fact Software RAID, is there any particular
reason to prefer one of the methods?


I know that Linux RAID will create a universal, more compatible array,
readable on any Linux machine. But is there some other reason that
makes it preferrable to use the SERVERAID driver provided by CentOS?
Is it optimized in any way that recommends its use?


Will the controller still make use of its cache and battery backup if
configured as a plain SCSI controller with Linux Software RAID?


I hope that some more experienced list member can ellucidate me on this.

Thank you!

PS - The machine is powered by a Intel P4 Xeon processor served by
2.5GB of RAM. The disks are 3 IBM 10K rpm SCSI 320 with 73 GB each.

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Hi Miguel,

FWIW I have been running an IBM e server 346 with 6 73GB disks in two
RAID volumes using the SERVERAID drivers for 3 years with no problems -
performance is mucj better than my development system that used single -
non-rad disks for various partitions.


ChrisG
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Old 11-18-2008, 07:05 PM
Fabian Arrotin
 
Default CentOS 5.2 with IBM SERVERAID 6i

miguelmedalha@sapo.pt wrote:
I need to install CentOS 5.2 on a IBM Server xSeries 226, which comes
with a IBM SERVERAID 6i RAID card. I think it is not a true hardware
RAID card. I has, nevertheless, an interesting feature: 128MB of cache
with battery backup.


It's a real raid adapter and the linux kernel is able to handle it with
the standard ips module




I launched the CentOS boot DVD and CentOS correctly identified the card
and the RAID 5 array as configured by the controller's BIOS.


My question now is: what would be the better way to implement RAID 5 on
this server? Should I use the detected array and respective driver or
should I delete the array and go for Linus Software RAID?


It's always up to you to decide but i'd prefer using the hw raid
controller in that case of course ...


If both solutions are in fact Software RAID, is there any particular
reason to prefer one of the methods?


If you use the hw raid, you can easily manager your raid array with
either ipssend cli or ServeRAID manager gui (both are downloadable from
IBM support website)




I know that Linux RAID will create a universal, more compatible array,
readable on any Linux machine. But is there some other reason that makes
it preferrable to use the SERVERAID driver provided by CentOS? Is it
optimized in any way that recommends its use?


Will the controller still make use of its cache and battery backup if
configured as a plain SCSI controller with Linux Software RAID?


I hope that some more experienced list member can ellucidate me on this.



Hope it's done now ;-)
PS : i've installed dozens of CentOS/RHEL on IBM machines without any
problems


--
-
Fabian Arrotin <fabian.arrotin@arrfab.net>
"Internet network currently down, TCP/IP packets delivered now by
UPS/Fedex ..."




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Old 11-18-2008, 07:43 PM
Miguel Medalha
 
Default CentOS 5.2 with IBM SERVERAID 6i

It's a real raid adapter and the linux kernel is able to handle it
with the standard ips module


I found some references in Google that seemed to indicate a "fakeraid"
controller, one that depends on the driver to do the RAID calculations...


It's always up to you to decide but i'd prefer using the hw raid
controller in that case of course ...


My fear is that in case of controller failure it will be difficult to
find in time a controller that recognizes the particular format of the
array, or that it will be too expensive. As an example, I recently tried
to buy the second processor for the machine (it originally came with
only one) and wanted more than 1500 dollars (yes!) for the P4 Xeon 3GHz CPU.


I am thankful for you for answers!
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Old 11-19-2008, 05:00 AM
Ian Blackwell
 
Default CentOS 5.2 with IBM SERVERAID 6i

miguelmedalha@sapo.pt wrote:
> My question now is: what would be the better way to implement RAID 5
> on this server? Should I use the detected array and respective driver
> or should I delete the array and go for Linus Software RAID?
>
I've installed RHEL 4 on several IBM eSeries servers with ServeRaid
controllers and I despise them. They fail too often and often don't
tell you that they are having problems until it is too late. My
suggestion is to use Linux software for your RAID array, and bypass the
ServeRaid controller entirely.

Ian
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Old 11-19-2008, 07:46 AM
"Tim Verhoeven"
 
Default CentOS 5.2 with IBM SERVERAID 6i

On Tue, Nov 18, 2008 at 9:43 PM, Miguel Medalha <miguelmedalha@sapo.pt> wrote:
>
>> It's a real raid adapter and the linux kernel is able to handle it with
>> the standard ips module
>>
> I found some references in Google that seemed to indicate a "fakeraid"
> controller, one that depends on the driver to do the RAID calculations...

All ServeRAID adapters from IBM are real hardware-based RAID cards.
The only exception are some cards then end with "e" in their name. But
all "ServerRAID Xi" cards are real HW RAID. Anyway, see here
"http://www.redbooks.ibm.com/abstracts/tips0054.html" for a complete
overview of all IBM ServeRAID cards.

I've run a lot of machines with these type of ServeRAIDs and they all
worked fine.

Regards,
Tim

--
Tim Verhoeven - tim.verhoeven.be@gmail.com - 0479 / 88 11 83

Hoping the problem magically goes away by ignoring it is the
"microsoft approach to programming" and should never be allowed.
(Linus Torvalds)
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Old 11-19-2008, 11:22 AM
Ralph Angenendt
 
Default CentOS 5.2 with IBM SERVERAID 6i

Fabian Arrotin wrote:
> If you use the hw raid, you can easily manager your raid array with
> either ipssend cli or ServeRAID manager gui (both are downloadable from
> IBM support website)

Faultdetection sucks with that, but you can use ipmitool for that:

[root@on3-3550 ~]# ipmitool sdr|grep Drive
Drive 1 Status | 0x01 | ok
Drive 2 Status | 0x01 | ok
Drive 3 Status | Not Readable | ns
Drive 4 Status | Not Readable | ns
[root@on3-3550 ~]#

Cheers,

Ralph
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Old 11-19-2008, 01:10 PM
Tom Diehl
 
Default CentOS 5.2 with IBM SERVERAID 6i

Ralph Angenendt wrote:


Fabian Arrotin wrote:
> If you use the hw raid, you can easily manager your raid array with
> either ipssend cli or ServeRAID manager gui (both are downloadable from
> IBM support website)

Faultdetection sucks with that, but you can use ipmitool for that:

[root@on3-3550 ~]# ipmitool sdr|grep Drive
Drive 1 Status | 0x01 | ok
Drive 2 Status | 0x01 | ok
Drive 3 Status | Not Readable | ns
Drive 4 Status | Not Readable | ns
[root@on3-3550 ~]#


I installed the OpenIPMI packages but when I run the above command
I get the following:

(geppetto pts5) # ipmitool sdr
Could not open device at /dev/ipmi0 or /dev/ipmi/0 or /dev/ipmidev/0: No such file or directory
Get Device ID command failed
Unable to open SDR for reading
(geppetto pts6) # rpm -qa | grep -i ipmi
OpenIPMI-libs-2.0.6-6.el5
OpenIPMI-2.0.6-6.el5
OpenIPMI-tools-2.0.6-6.el5
(geppetto pts6) # lsmod | grep -i ipmi
(geppetto pts6) #

Is there something special that needs to be done to enable ipmitool? lsmod
shows that
none of the ipmi modules are loaded. Do I need some magic incantation in
/etc/modules.conf or is there some other package I need?

the machine is an ibm X3655 with C5 installed on it.

Regards,

--
Tom Diehl tdiehl@rogueind.com Spamtrap address mtd123@rogueind.com
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