If using SSD caching, if single SSD fails due to brownout, will you lose data?

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jang430
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If using SSD caching, if single SSD fails due to brownout, will you lose data?

Post by jang430 »

Again, asking for TS-873A, it has 2 m.2 ssd slots. If we only use 1 m.2 slot for caching, do we risk losing data when SSD fails, or brownout? I'm talking about ZFS filesystem.
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dolbyman
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Re: If using SSD caching, if single SSD fails due to brownout, will you lose data?

Post by dolbyman »

if it is write caching ..yes
jang430
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Re: If using SSD caching, if single SSD fails due to brownout, will you lose data?

Post by jang430 »

What will be the way to protect against this, aside from the UPS?

Will having another SSD in some sort of raid help?

Isn't SSD caching about anticipating/ reading data that is on the storage? So the main source will still be in the storage right? Does support write caching? Write to SSD first before transfering to storage? In that case, I can see why data might be lost.
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dolbyman
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Re: If using SSD caching, if single SSD fails due to brownout, will you lose data?

Post by dolbyman »

either use raid1+ on your cache drive or only use read cache ...that's it
jang430
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Re: If using SSD caching, if single SSD fails due to brownout, will you lose data?

Post by jang430 »

Hi. How will raid1+ protect against this?

I've read that when writing to ZFS, it first writes it to RAM. How long does it take before transfering to disk? What if file you are writing is bigger than the ram allocated to the NAS, e.g. 16 GB only, and the file is 32 GB?
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dolbyman
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Re: If using SSD caching, if single SSD fails due to brownout, will you lose data?

Post by dolbyman »

If one drive in raid1+ breaks..the remaining drives still have redundancy

you can ask qnap support all destaging and cache behavior questions ..maybe they know the answer
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