[mythtv-users] XFS RAID Tweaking

belcampo belcampo at zonnet.nl
Fri Oct 22 13:08:30 UTC 2010


Rob Dege wrote:
> Hi Keith,
> 
> I'm not having any problems with my RAID atm.  In fact things are 
> working fine :)
> 
> I was forced to upgrade the mysql server on my mythbox, and was 
> searching for ways to optimize it, when I stumbled upon that wiki page.  
> Reading the entire page, I discovered that my XFS /myth partition was 
> 98% fragmented, which forced me to upgrade xfsprogs so that I could 
> defrag the drive (the version that was installed didn't have the defrag 
> utility).
To almost prevent fragmentation, you can add allocsize=512M or 1024M to 
your xfs mount options in fstab.
At least xfs_fsr will be much faster because of much less fragmentation.
> 
> After seeing this success, I wanted to try and tweak XFS on RAID.  
> However, I don't know if I can tweak the mount options if the sunit and 
> swidth were specified when I originally formatted the partition.  Hence 
> my question (btw, do you know if that's advisable or not?)
> 
> Thank you for your concern about my RAID setup, but I'm okay with the 
> risks.  The partition only holds the recorded TV shows, and I'm okay if 
> they get lost in a RAID crash.  I chose a RAID0 over a RAID1 setup b/c 
> of the improved performance.  I have 5 tuners on my box (3 SD, 2 HD), 
> and I needed the extra write performance to handle all 5 tuners 
> recording at once while I simultaneously watch a show.
> 
> Thank you for the mentioning the tip about mdadm's email alerts.  I'll 
> have to look into that.  I like the idea of that feature.  I just hope 
> it was available when FC3 was released :)
> 
> -Rob
> 
> 
> On Thu, Oct 21, 2010 at 5:51 PM, Keith Edmunds <kae at midnighthax.com 
> <mailto:kae at midnighthax.com>> wrote:
> 
>     On Thu, 21 Oct 2010 14:13:11 -0400, livemotion at gmail.com
>     <mailto:livemotion at gmail.com> said:
> 
>      > is it okay to
>      > add the custom sunit and swidth values to the mount options, even
>     though
>      > they wouldn't match the values on the partition?
> 
>     What problem do you have that you are trying to solve?
> 
>     An observation: with RAID0, you will lose all the data on the RAID
>     device
>     if any of the underlying physical devices fail. You're already three
>     years
>     nearer the time when the first of those disks to fail will actually
>     do so.
>     You don't say what size your RAID0 partition is, but you may want to
>     consider buying two disks that are each (at least) the size of your
>     RAID0
>     partition, and implementing them as RAID1, therefore giving you some
>     fault
>     tolerance. If you do that, set up mdadm to email you if the array
>     becomes
>     degraded.
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> 
> 
> 
> 
> -- 
> -Rob
> 
> Hell hath no fury like a snowplow driver from Cheektowaga who gave
> up cable and Canadian beer so he could afford Bills season tickets.
> 
> 
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> 
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