[SATLUG] Software RAID suggestions

FIRESTORM_v1 firestorm.v1 at gmail.com
Wed Mar 3 03:29:09 CST 2010


Hey all, well I _finally_ gave up on trying to use the RAID card as a
RAID card and figured I can beat the snot out of software raid before
I let the server go live to check on data errors, etc.

I noticed something odd about this setup and after a while, I did end
up killing this build.  I did some research and noticed that if I used
--force (to force mdadm to use only the drives I specified) mdstat
showed [UUUU] and appears to be rebuilding properly.  An additional
change I made is I went in and created partitions and made them all
type fd (linux raid auto) and went into the RAID card's BIOS and made
sure that the disks weren't in JBOD mode.  Although Linux saw the four
drives, it really freaked out on the partition types but fdisk led me
to believe the drives were ready to go.

Now, the only concern I have is that when the server reboots, will
mdadm mount the RAID using all four drives like I specified or will it
break the array at boot requiring me to rebuild it again manually?

When I did the reinstall after making sure that the card was set for
JBOD, the installer saw the four drives but proceeded to mark the
fourth offline. [UUU_]

When I used mdadm --stop /dev/md0 and then respecified my mdadm create
command with --force it did not generate any errors and is creating
the array as I designated with all drives marked online.  I guess now,
it's the waiting game as I wait an almost 36 hours for the array to
build.

Since we're on the subject, can anyone recommend a PCI 4 port SATA
card that doesn't have RAID on it and that works well with Linux?  I
found a $30 card that uses the silicon labs chipset, but the most
recent data I could find on it regarding linux support was from over
two years ago and that it wasn't very good.

Also, (and I'm sure this is a stupid as heck question) since I'm using
software RAID, would a faster proc mean better throughput?  Right now
the "server" is a P-II 300MHz with 512MB RAM and was wondering if I
will need to dig a better machine out of storage (think I have a P-III
850 somewhere using 256MB RDRAM) but getting it out of storage is
going to take an act of god and an act of congress.

This isn't going to be a "high load" server, just a fileserver for
XBMC and windows files.

Thank you all for your suggestions, it's definitely a learning experience.

FIRESTORM_v1



On Fri, Feb 26, 2010 at 4:51 PM, Jeremy Mann <jeremymann at gmail.com> wrote:
> On Fri, Feb 26, 2010 at 1:39 PM, FIRESTORM_v1 <firestorm.v1 at gmail.com> wrote:
>
>> My only concern is that the third line [UUU_] looks a little odd.   I
>> expected [UUUU] since I have 4 SATA drives and I specified their
>> devices on the commandline:
>>
>> #  mdadm --create /dev/md0 --level=5 --raid-devices=4 /dev/sdb
>> /dev/sdc /dev/sdd /dev/sde
>>
>> I don't recall anyone specifying what the [UUU_] but can someone tell
>> me if I'm chasing ghosts or letting myself get too nervous?
>
> Matt, "_" means one drive is offline, but that could be the one that
> is rebuilding. Once its finished check it again with :
>
> cat /proc/mdstat
>
> If it still shows one drive as "_", you got problems and your RAID
> array is running in degraded mode.
>
>
> --
> Jeremy Mann
> jeremy at biochem.uthscsa.edu
>
> University of Texas Health Science Center
> Bioinformatics Core Facility
> http://www.bioinformatics.uthscsa.edu
> Phone: (210) 567-2672
> --
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