Experience with 5400 RPM CMR Drives

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abcdefg

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May 24, 2023
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I need to replace my aging disk array. It is currently i5-2500K, 32GB (non-ECC) RAM, 2 mirror ZFS vdevs HGST 3TB 7200 RPM drives. Since the array is on continuously and sees light usage most of the time, I'd like to put more effort into reducing the power usage.

One of the areas I am considering is switching from 7200 RPM drives to 5400 RPM drives, something like WD Red Plus. What have people's experience been with 5400 RPM drives in ZFS arrays?
 

BlueFox

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Oct 26, 2015
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You're looking at 1-1.5W difference. Negligible in the grand scheme of things. ~$1 in electricity annually assuming they never spin down. You're better off with fewer larger drives or a newer CPU.
 

i386

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Mar 18, 2016
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What have people's experience been with 5400 RPM drives in ZFS arrays?
a bunch of the "5400 rpm" hdds are actually 7.2k rpm hdds, especially the bigger ones like >8tb (source:September | 2020 | Ars Technica
I have a few of the 10tb reds in a hardware raid 10. They are okay but I would prefer newer and bigger ones as they are faster and could replace multiple reds at once.

*this bs from wd made me stop buying anything but enterprise/datacenter hdds (from seagate :D)
 

mr44er

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Feb 22, 2020
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What have people's experience been with 5400 RPM drives in ZFS arrays?
"It works" the same. Technically the whole vdev is throttled down to the speed throughput of the slowest drive. So if you have low quality 7200er spinners that reach ~150MB in sequential write and one good 5400er that can do ~130MB seq. write, the vdev goes down to ~130. Another story is random access, but thats slow even with 15000k spinners and - random, without guarantee that the request hits exactly this disk. Mixing rpms is no fail, it's just not optimised and if your pool has enough disks and vdevs, you likely don't notice it. Pure waste of money would be a 50/50 mix of 15000k and 5400k in the pool, but it will work.
BlueFox is right, the difference is 1W per disk, if at all. Also the 5900rpm-version from Seagate? I never understood...as slow-eco-idle-mode for every disk ok, sure. But useless as a whole model.

I'd like to put more effort into reducing the power usage.
Are your HGST SAS or SATA? SAS has often very nice options in the modepages to set energy savings, SATA not always and also the settings reset sometimes on cold reboot (really depends).