3ware 7500-8 confusion

3ware 7500-8 confusion

[Alvin Oga]

hi ya Raiders

okay... i confess ... i'm lost and confused ...

we have a dual amd mb + 9 drive bays w/ 200GB drives

the drives are connected to a 3ware 7500-8
and the drives is recognized during bios bootup and linux-2.4.19/20
bootup recognized the controller too

the 3ware bios created the raid array out of the 8 drives
( supposedly .. waited a long time for it to finish )

3dm was installed from the cdrom that came w/ the controller

http://localhost:1080
	- shows the list of drives in the raid
	- shows the other info abut the 3ware card

but now that i wanna use the hw raid, and want to do:
	fdisk /dev/md0
	mke2fsc -j -m 1 /dev/md0
	mount /dev/md0 /Raid

but there is no such thing as /dev/md0 ... *pout*

what is the name of the device ( /dev/xxx ) that 3ware built ??
	- went digging/googling around but didnt find my answer yet

	for freebsd ... i think its /dev/twed

-- if its supposed to be /dev/md0 ... guess some step along the
   way is missing in the steps i did to configure the 3ware 7500-8 card

	-- ie .. i dont see the 3ware bios section that allows
	a JBOD vs raid5 either... so its defaulted to raid5 for now
 
-- after all this is done .. guess i'll have to write up another 
   itty-bitty 3ware-raid-howto

thanx
alvin

Re: 3ware 7500-8 confusion

[Gregory Leblanc]

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On Sat, 2003-02-22 at 21:08, Alvin Oga wrote:
> hi ya Raiders
> 
> okay... i confess ... i'm lost and confused ...
> 
> we have a dual amd mb + 9 drive bays w/ 200GB drives
> 
> the drives are connected to a 3ware 7500-8
> and the drives is recognized during bios bootup and linux-2.4.19/20
> bootup recognized the controller too
> 
> the 3ware bios created the raid array out of the 8 drives
> ( supposedly .. waited a long time for it to finish )
> 
> 3dm was installed from the cdrom that came w/ the controller
> 
> http://localhost:1080
> 	- shows the list of drives in the raid
> 	- shows the other info abut the 3ware card

Sounds like you've got things set up correctly.

> but now that i wanna use the hw raid, and want to do:
> 	fdisk /dev/md0
> 	mke2fsc -j -m 1 /dev/md0
> 	mount /dev/md0 /Raid
> 
> but there is no such thing as /dev/md0 ... *pout*

Err, right, there isn't.  /dev/md? is only for software RAID devices. 
If you've got the 3ware kernel modules loaded, then your 3ware RAID
device should show up as /dev/sd?  dmesg should have more info, or
/proc/scsi.

> what is the name of the device ( /dev/xxx ) that 3ware built ??
> 	- went digging/googling around but didnt find my answer yet
> 
> 	for freebsd ... i think its /dev/twed
> 
> -- if its supposed to be /dev/md0 ... guess some step along the
>    way is missing in the steps i did to configure the 3ware 7500-8 card
> 
> 	-- ie .. i dont see the 3ware bios section that allows
> 	a JBOD vs raid5 either... so its defaulted to raid5 for now

There is a way to configure the 3ware card to just work as JBOD.  I
don't recall what it is offhand (I've got an older card with only 4
ports as well).  It doesn't seem to make much sense to buy a pretty nice
RAID card like this one and then not use it's RAID features, though. 
HTH,
	Greg

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Re: 3ware 7500-8 confusion

[Alvin Oga]

hi ya greg, maurice

thanx for the reply....
	- its formatting 1.4TB now...

duhhh.... guess i'm getting too old and too late for this...

i got confused since i had dinitially done a
	fdisk /dev/sda  ... /dev/sdh  and
	created partitions just to make sure everythng worked

than i did the 3dm configure stuff...


thanx
alvin

> > 
> > http://localhost:1080
> > 	- shows the list of drives in the raid
> > 	- shows the other info abut the 3ware card
> 
> Sounds like you've got things set up correctly.
> 
> > but now that i wanna use the hw raid, and want to do:
> > 	fdisk /dev/md0
> > 	mke2fsc -j -m 1 /dev/md0
> > 	mount /dev/md0 /Raid
> > 
> > but there is no such thing as /dev/md0 ... *pout*
> 
> Err, right, there isn't.  /dev/md? is only for software RAID devices. 
> If you've got the 3ware kernel modules loaded, then your 3ware RAID
> device should show up as /dev/sd?  dmesg should have more info, or
> /proc/scsi.
> 

Re: 3ware 7500-8 confusion

[Maurice Hilarius]

With regards to your message at 11:03 PM 2/22/03, Gregory Leblanc. Where 
you stated:
>There is a way to configure the 3ware card to just work as JBOD.  I
>don't recall what it is offhand (I've got an older card with only 4
>ports as well).  It doesn't seem to make much sense to buy a pretty nice
>RAID card like this one and then not use it's RAID features, though.
>HTH,
>         Greg

Actually it makes tons of sense.
If you are using it for RAID5 you will get at least twice the performance.
Yes, to echo an earlier message, you will get higher CPU load.
That is to be expected when your writes take half as long.
AND, as a bonus, if you partition each drive, leave a small partition at 
the beginning of each disk you gain two things:
1) You can make your system boot off the disks without the md RAID driver 
being loaded, so emergency recovery is simpler
2) If you lose a disk at a later date, you don;t have to worry about 
getting the same exact drive to replace it with.

What you lose is:
1) 3Wares nifty 3DM tool

Still, you get most of its functionality with their CLI utility.


With our best regards,

Maurice W. Hilarius       Telephone: 01-780-456-9771
Hard Data Ltd.               FAX:       01-780-456-9772
11060 - 166 Avenue        mailto:maurice@harddata.com
Edmonton, AB, Canada      http://www.harddata.com/
    T5X 1Y3

Re: 3ware 7500-8 confusion

[Joshua Baker-LePain]

On 23 Feb 2003 at 12:53am, Maurice Hilarius wrote

> Actually it makes tons of sense.
*snip*
> 2) If you lose a disk at a later date, you don;t have to worry about 
> getting the same exact drive to replace it with.

Don't most hardware RAIDs (including the 3ware) deal just fine with 
dissimilar new disks, as long as their block count is >= that of the 
original disks?  My external IDE-SCSI unit does this, and I know my 3wares 
deal with disks with different rotation speeds.

-- 
Joshua Baker-LePain
Department of Biomedical Engineering
Duke University

Re: 3ware 7500-8 confusion

[Gregory Leblanc]

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On Mon, 2003-02-24 at 06:41, Joshua Baker-LePain wrote:
> On 23 Feb 2003 at 12:53am, Maurice Hilarius wrote
> 
> > Actually it makes tons of sense.
> *snip*
> > 2) If you lose a disk at a later date, you don;t have to worry about 
> > getting the same exact drive to replace it with.
> 
> Don't most hardware RAIDs (including the 3ware) deal just fine with 
> dissimilar new disks, as long as their block count is >= that of the 
> original disks?  My external IDE-SCSI unit does this, and I know my 3wares 

Yes, generally.  This isn't the only potential problem, though. 
Sometimes if a drive fails and you receive a warranty replacement form
the manufacturer, it may be rated at the same capacity, but may actually
have less blocks available.  The 3ware cards work around this by making
RAID array pieces slightly smaller than the size of the smallest drive,
I believe.  However, it appears that they aren't capable of using all of
the available capacity when you try to use different size drives.

> deal with disks with different rotation speeds.

Rotation speeds don't come in to play here.  I doubt that the 3ware card
does anything "intelligent" about drives with markedly different
transfer rates.  I'm not sure I'd care to figure out the logic of how to
do that, either.
	Greg


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Re: 3ware 7500-8 confusion

[Luca Berra]

On Sat, Feb 22, 2003 at 09:08:04PM -0800, Alvin Oga wrote:
>3dm was installed from the cdrom that came w/ the controller
>
you may want to look in tw_cli (3ware commandline client)
you can download it from 3ware site
3dm sucks

>but now that i wanna use the hw raid, and want to do:
>	fdisk /dev/md0
>	mke2fsc -j -m 1 /dev/md0
>	mount /dev/md0 /Raid
>
>but there is no such thing as /dev/md0 ... *pout*
>
>what is the name of the device ( /dev/xxx ) that 3ware built ??
>	- went digging/googling around but didnt find my answer yet

3ware is seen as a scsi controller
/dev/sd*
cat /proc/partitions helps a lot

-- 
Luca Berra -- bluca@comedia.it
        Communication Media & Services S.r.l.
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