[mythtv-users] RAID using two drives per PATA channel ?

[Alexander Fisher]

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Jens Axboe wrote:
> On Mon, Jul 31 2006, Alexander Fisher wrote:
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>> Steven Adeff wrote:
>>> anyone have any insight in to whether when neglecting possible card or
>>> cable failure, would using two drives on a single PATA channel for a
>>> RAID 10 array to add two more drives lead to an overall increase in
>>> the array speed, or would the speed loss be too great for the extra
>>> drives to help any?
>> According to the linux RAID HOWTO...
>> http://www.tldp.org/HOWTO/Software-RAID-HOWTO-4.html#ss4.1
>> 'It is very important, that you only use one IDE disk per IDE bus. Not
>> only would two disks ruin the performance, but the failure of a disk
>> often guarantees the failure of the bus, and therefore the failure of
>> all disks on that bus.'
>>
>> Then again, the HOWTO is somewhat out of date.  Perhaps dieing disks
>> killing the bus is just folklore?
> 
> Nope, that one still holds true. If the broken drive locks up the
> bus, the other drive will be inaccessible as well.
> 
> Old parallel IDE has no concept of bus release, like SCSI. Access to the
> bus is thus always serialized between the two drives, so you will see a
> performance loss as well.

I wish more mailing list replies could be this authoritative, (like mine
for example)!
Nothing quite works the same as *the* Linux kernel block layer subsystem
maintainer putting you in your place :)

Respectfully,
Alex

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