[mythtv-users] Hard Drive reliability esp. RAID issues

[Harry McGregor]

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On 3/8/10 7:15 PM, John Drescher wrote:
>> For my home use, I use RAID6, with 14 1TB drives, plus a hot
>> spare.
>>
>> I am considering moving towards some raid10 groups instead for
>> greater performance.
>
> Do you need better performance? A 14 drive linux software array of
> 1TB drives should net you at minimum 500MB/s writes with 600 to 800
> MB/s reads.
That is in sequential read/write

When you start throwing a lot of streams at it, think 3-6 tuners, 3
front ends, maybe a few com flag processes, you can still have IO
stall conditions.  If front end X wants Y blocks, and has to wait too
long for them, you will see skips on the the player.

I am thinking of doing 2 RAID10 groups, and setting up storage groups
for them, that would get me 7TB of usable storage vs the current 12TB,
which would be a little painful

Another option I have is to do a two drive raid 1, and put the mysql
DB on it.  That would keep me at a 12 drive raid6, plus a 2 drive
raid1, plus a hot spare, this would be me 10TB + 1TB of usable storage
probably more practical. I can't use my boot drive for mysql, as that
is an 8GB CF card, and I am not ready to drop the cash for a full
scale SSD for the boot volume.

What I deal with for work is optimized for many threads, and has a
very effective predictive read ahead.  Your average linux software
raid does not do quite so well with many threads, especially on a raid
6.  I am using Marvel SATA chipsets, on a PCI-X bus.

My home RAID6 gets on average 350MB/sec out of hdparm on a simple read
test, but again, that is a single thread of sequential IO.

                                Harry

> John _______________________________________________ mythtv-users
> mailing list mythtv-users at mythtv.org
> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
>

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