[mythtv-users] Question re: available SATA ports and linux software RAID
linux at thehobsons.co.uk
Sun Apr 10 21:40:14 UTC 2011
Bobby Gill wrote:
>I suppose the last hurdle is to determine whether or not to build
>one big array or perhaps 2 or more separate ones. I am set on a
>minimum of 6 drives, likely 8, x 2 TB, and RAID 6. I'm currently
>simulating rrays in Virtualbox to fiddle around and get some
>experience doing it myself first.
>What are key considerations if for example I have 6 x 2 TB, in doing
>a 6x2TB array vs. say, 2 x 3x2TB? I don't want to overcomplicate
>things so if one big array is a fine path I'll do it, but this
>thread has shown me how frakkin much "fine print" there is with the
>whole RAID deal :)
OK, for Myth storage there is a school of thought that says not to
build an array at all - just create multiple storage directories and
that will allow Myth to spread the recordings (and load) between them.
In terms of capacity, it depends on the level of raid.
If striping, then there is no difference in capacity between 2x3 and
1x6 in the array - both will give you a total of 3 drives worth of
However, for RAID 5 then 1x6 will give you 5 drives worth of storage,
while 2x3 will give you 4 drives worth (2x2). RAID 6 would give 4
drives worth for 1x6, but would not be worthwhile for 2x3 since 3
drives would only give a single data drive for RAID 6 !
For performance, it is very heavily dependent on the type of
workload. For the sort of large sequential reads & writes typical of
Myth recordings, then 2 arrays may give better performance - but that
assumes multiple recordings will be split across the arrays (which is
the norm) and that playback will be similarly split (which may or may
not be the case). In practice, a single large array should be quite
adequate for any reasonable setup.
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