Re: Possible to use multiple disk to bypass I/O wait?

[Thomas Harold <thomas-lists@xxxxxxxxxx>]

On 6/9/2011 1:26 PM, John R Pierce wrote:
> On 06/09/11 2:24 AM, Emmanuel Noobadmin wrote:
>> Alternatively, if I mdraid mirror the existing disk, would md be smart
>> enough to read using the other disk while the first's tied up with the
>> first process?
>
> that woudl be my first choice, and yes, queued read IO could be
> satisfied by either mirror, hence they'd have double the read performance.
>
> next step would be a raid 1+0 with yet more disks.
>

mdadm is good, but you'll never get double the read performance.  Even 
on our 3-way mirrors (RAID 1, 3 active disks), we don't come close to 
twice the performance gain.

RAID 1+0 with 4/6/8 spindles is the best way to ensure that you get 
better performance.

Adding RAM to the server so that you have a larger read buffer might 
also be an option.
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