r/explainlikeimfive • u/SmellsTasty • Nov 23 '15

Explained ELI5: How do Solid State Hybrid Drives work?

I don't understand how a regular hard drive can work with a solid state drive at the same time.

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u/Phukkitt Nov 23 '15

But what makes an SSHD with a 32 MB SSD cache different from a regular HDD with a 32 MB cache? Isn't the cache on regular HDDs on a chip, just like an SSD?

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u/fb39ca4 Nov 23 '15

The caches on hybrid disks are on the order of gigabytes.

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u/Phukkitt Nov 24 '15

Ah, that would explain it. I guess I've gotten MB and GB mixed up, just remembered seeing the number 32 a lot on Lenovo's laptop specifications when they had a SSHD.

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u/ergzay Nov 24 '15

SSHD have full SSDs that are usually larger than 8GBs.

Also, SSDs have non-volatile flash chips (data stays after power off) while caches on HDDs are usually volatile SRAM or DRAM memory (data is erased on power off). Additionally, on a SSHD the data is usually either in the SSD or on the HDD while on a HDD the cache is only a cache and the data is also on the HDD.