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How does Linux software raid-1 work across disks of dissimilar performance.

Would a raid-1 across ssd and hdd partitions give me a mirror of the ssd contents while not impacting the read speed? I only need good read speed.

Or will it just distribute "reads" round-robin between the drives, giving poor read performance?

(I understand and accept that write performance will be as slow as a hdd.)

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How do you create that raid1? LVM or MDADM? – Nils Jun 17 '13 at 13:16
I am familiar with mdadm. Are there TRIM problems with 'nested' SSDs? – chrisdew Jun 17 '13 at 14:53

From the mdadm-developer-blog I would say - you need at least the 3.2.1 version with that policy-stuff. This sounds as if you can define one member as spare instead of using it for active reading/writing. So in your case the harddisk should be the spare.

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