Hi, the ZFS_Best_Practises_Guide states this:
"Keep vdevs belonging to one zpool of similar sizes; Otherwise, as the pool fills up, new allocations will be forced to favor larger vdevs over smaller ones and this will cause subsequent reads to come from a subset of underlying devices leading to lower performance."
I am setting up a zpool comprised of mirrored LUNs, each one being exported as a JBOD from my FC RAIDs. Now, as the zpool will fill up, I intend to attach more mirrors to it and I am wondering, if I understood that correctly.
Let's assume I am creating the initial zpool like this: zpool create tank mirror disk1a disk1b mirror disk2a disk2b mirror disk3a disk3b mirror disk4a disk4b. After some time the zpool has filled up and I attach another mirror to it: zpool attach tank mirror disk5a disk5b, this would mean, that all new data would take a performance hit, since it can only be stored on the new mirror disk, instead of being distributed across all vdevs, right?
So, to circumvent this, it would be mandantory to add at least as many vdevs at once, to satisfy the desired performance?
How do you guys handle this? Cheers, budy
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