How to evaluate redis on flash?

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Madhur Ahuja

Nov 9, 2021, 5:54:37 AM11/9/21
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I want to evaluate redis on flash for some of our use cases. Is it available in free version? From the documentation it seems no.

Is the only way to evaluate shell out money? Any faster alternative?


Greg Andrews

Nov 9, 2021, 11:51:56 PM11/9/21
to Redis DB

It's not easy to understand exactly what you want.  There seem to be two possibilities:
  1. You want a version of Redis that holds its active database in RAM and also writes/reads some of the database to SSD/NVME (flash) memory.
  2. You want to run Redis on a server that will swap some active RAM pages to SSD/NVME (flash) memory.
Since you're looking at Redis documentation, implying you expect Redis to have explicit support/control of the data stored in flash, it's likely you're looking for #1.

Have a look at this discussion thread from several years ago, talking directly about #1 and indirectly about #2.  The creator of Redis gives the reason Flash is not good for Redis in the middle of the thread, but for full details see the timing comparison in the last message of the thread (disclaimer: written by me).

Summary:  Compared to RAM, Flash is way too slow.  Putting the speed comparison into human timescales, if reading from RAM takes one second, reading from flash takes five and a half hours.  (best-case HD takes four and a half days)


Nov 10, 2021, 1:58:41 AM11/10/21
U can have a look at which may be what we want. I agree with Greg that SSD was too slow when compared with RAM, it's the trade-off between the latency and cost(or capacity). BTW, the latency was good enough for many scenes since the flush device throughput and latency were improved a lot those years.

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David Maier

Nov 10, 2021, 4:37:00 AM11/10/21
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just to clarify Redis on Flash is a feature that is offered by Redis Enterprise. It automatically keeps hot data (most often accessed) in RAM and evicts warm/cold data to a Flash drive. This allows you cost-effective storage tiering (e.g., RAM + Flash as RAM extension + Persistent storage).

We don't use this forum here for Sales purposes. @Madhur: I propose that you reach out to the Redis sales team. You could use the following website to do so: Another option to get your hands on it, would be to use a Flexible plan of Redis Cloud ( Hope this helps.

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