MythTV storage

[feenberg at nber.org (Daniel Feenberg)]

On Sun, 24 Dec 2006, Robert La Ferla wrote:

> On a related note, I just picked up a couple of 500GB SATA drives for a 
> audio/video jukebox server.  What RAID configuration would you use?  If I 
> were to buy a 3rd drive, what RAID configuration would you use?
>

With two drives you only have three choices - JBOD, RAID 0 or RAID 1. 
Notice that JBOD has the same rate of failure and storage capacity as RAID 
0, but only half the data loss on each failure. We find that significant, 
but I never see it mentioned in the storage literature, or in newsgroups.

With three drives you could do a RAID 5. But with the Linux driver,
RAID 5 is very problematic. Have a look at my piece

     http://www.nber.org/sys-admin/linux-nas-raid.html

where I explain why drive failures often come in pairs (a third of the way 
down the page). The fault lies with the Linux md driver, which stops 
rebuilding parity after a drive failure at the first point it encounters a 
uncorrectable read error on the remaining "good" drives.


Daniel Feenberg


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