Date: Sat, 5 Dec 2020 05:24:44 -0800 From: Mel Pilgrim <list_freebsd@bluerosetech.com> To: freebsd-fs@freebsd.org Subject: Re: vdevs with different spindle speeds Message-ID: <fb1e2d3c-f029-c798-1c95-ac007b6daa70@bluerosetech.com> In-Reply-To: <X8t/X4VRfMVzXaRi@rpi4.local> References: <X8t/X4VRfMVzXaRi@rpi4.local>
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On 2020-12-05 4:38, tech-lists wrote: > Normally when making an array, I'd like to use all disks all same speed, > interface, make and model but from different batches. In this case, I've no > choice, so we have multiple 1TB disks some 7.2k some 5.4k. I've not mixed > them like this before. > > What effect would this have on the final array? Slower than if all one or the other? > No effect? I'm expecting the fastest access will be that of the slowest vdev. > > Similarly some disks block size is 512b logical/512b physical, others are 512b > logical/4096 physical, still others are 4096/4096. Any effect of > mixing hardware? I understand zfs sets its own blocksize. Make sure you have ashift=12 for everything and you'll be fine. The marginal increase in latency with the 5400 rpm drives will disappear behind ZFS' heavily-cached, asynchronous operation unless you're hammering the pool with calls for cold data. If you're really worried about it, get a cheap SSD and use it as a cache device.
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