[mythtv-users] Slighty OT: Software raid mdadm online capacity expansion (OCE) success

[Steven Adeff]

On 10/14/06, Gene Stapp <genestapp at gmail.com> wrote:
> Steven Adeff wrote:
> > On 10/14/06, Gene Stapp <genestapp at gmail.com> wrote:
> >> Just thought I'd let everyone know I was able to do a raid 5 disk
> >> expansion in mdadm software raid with no ill effects. I used mdadm 2.5.4
> >> (built from source) and supposedly it is pretty safe. Following this
> >> page as a guide and it worked perfectly. Took about 6 hours to reshape
> >> the array. From 300gb x 4 raid 5 to 300gb x 5 raid 5. No lvm just an md0
> >> mdadm device and I was still able to make 2 simultaneous HD recordings
> >> and watch an HD recording while this was going on.
> >>
> >> page used as guide:
> >> http://scotgate.org/?p=107#comments
> >>
> >> for me the process was:
> >> |mdadm --add /dev/md0 /dev/sde1|
> >>
> >> then:
> >> |mdadm --grow /dev/md0 --raid-devices=5
> >>
> >> |to find details about your raid reshaping status use:
> >> cat /proc/mdstat
> >>
> >> to speed up reshaping use (fill in whatever speed you want where the
> >> 100000 is. Default is 10000 :
> >> echo -n 100000 > /proc/sys/dev/raid/speed_limit_max
> >>
> >> The only difference for xfs is to use the:
> >>  xfs_growfs (path to mounted raid filesystem)
> >>
> >> Hope this is helpful as I didn't see anything in the archives on this topic,
> >> Gene
> >>
> >
> > great to hear. I've been looking at building a RAID5 array in two
> > parts (to spread out the costs), one of the things I was looking for
> > was information on how long the process takes.
> >
> > Any idea what the speed_limit_max does?
> >
> >
> The speed_limit_max entry there controls how fast the raid array
> rebuilds (how much of the array's bandwidth is available to the rebuild
> process).  Make that bandwidth number higher and it goes faster but uses
> more of the throughput of the hard drives (leaving less available to say
> Myth recording on the degraded array). Using the info I posted earlier
> while you are waiting for the reshaping to finish, the array is in a
> degraded state.

gotcha, thanks!

-- 
Steve
Before you ask, read the FAQ!
http://www.mythtv.org/wiki/index.php/Frequently_Asked_Questions
then search the Wiki, and this list,
http://www.gossamer-threads.com/lists/mythtv/
Mailinglist etiquette -
http://www.mythtv.org/wiki/index.php/Mailing_List_etiquette