How to combine an SSD with two HDDs in a RAID1-ish hybrid setup?

Tobias Kienzler

1/25/24, 12:04 PM

Coming from Linux SSD as HDD cache, I'd like to set up an SSD (or rather a partition thereon) as cache for basically a RAID1 of two HDDs. But since the data might remain cached on the SSD for while, I was wondering it is possible to set up the HDDs such that they first behave more like RAID0, i.e. the data from the SSD is written striped for better speed, and only afterwards RAID1-synced between the two.

Is that even sensible let only feasible and if so, how? If not, what would be a good setup with 1 SSD and 2 HDDs to benefit from both speed and redundancy if the total capacity is acceptably limited to 1x HDD? I'm using btrfs if this is helpful or a hurdle.

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Chopper3

1/25/24, 12:56 PM

I never like the idea of delayed synching but either way what you need is bcache - sounds ideal for what you want to do.

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Nikita Kipriyanov

1/25/24, 1:20 PM

I doubt it is possible to marry BTRFS-based RAID and bcache for caching. Especially when there is a single SSD and so you basically are restricted to write-through or write-around cache.

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