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MegaRAID Cache

07-09-2014, 17:26
nebulos, IMHO, a properly tuned mdadm-based raid5 is the best choice.
Take a look at these docs: (especially md/stripe_cache_size, md/preread_bypass_threshold).
Also take care about the TRIM/discard support by your kernel. (e.g. RHEL6 is limited to TRIMming only on RAID 0/1/10).

07-09-2014, 10:59
The cache isn't just about performance, though. It could save your data in the event of power loss or system lockup as it will flush all pending writes to the disk once power is restored.

07-09-2014, 09:41
so what you're saying is that if i have 3 SSDs, I want to use them in raid 5, it's better to use software raid than the "MegaRAID Cache"?

07-09-2014, 02:56
I see no reason to use the hardware raid option with ssd drives since it will be a serious overhead by a random i/o (3-4 times slowdown according to my tests).

The best option is a software raid which gives you a full performance.

06-09-2014, 22:31
i will wait for answer like you

05-09-2014, 17:45

Ok.. I've read about what it does..

but how much does it help?
Is it worth the extra price? If yes, how do I use it..
Oh and if the server has only SSDs, does it still help?

anything else I should know about MegaRAID Cache??