1/3/2024 0 Comments Replacement for 3hubThey have to use physical volumes of the same size and are relatively cumbersome to upgrade. Most hardware RAIDs (and software raids like mdraid) are static in nature, which is limiting. I would really recommend checking out the Level1Techs video, it was pretty surprising for me. I’m not arguing software RAID over hardware RAID. It is hardware RAID vs erasure coding or ZFS. I definitely agree that hardware RAID vs software is a totally different discussion. You’re comparing software vs hardware RAID, that’s not the comparison I’m making. The truth is that there are pros and cons for each approach, the weights of which can vary for different people. I’m not trying to overlook the cons, like hardware being a potential point of failure, but I don’t feel the assertion “Hardware raid is basically dead” as a blanket statement is justified. This isn’t really the fault of software raid, however it is a limitation due to the fact that software has to be prepared for a system reset/shutdown at any clock cycle whereas hardware can be designed to shut down gracefully using it’s own battery/super-capacitor to save it’s state and do a graceful shutdown independently of the OS and host. Raid level 6 is much better in hardware because hardware can implement write-back semantics that software cannot. Write caching can be a huge boon to performance in many kinds of workloads like databases that otherwise have to block on writes constantly. Also the system bandwidth needed to do raid in software is higher than in hardware. Hardware raid is more robust against drive failures that would leave the OS unable to boot. While hardware raid has some cons, so does software raid. Might surprise you how unreliable those hardware raid cards actually are in ensuring you read back what you wrote. Even high end SANs don’t use hardware raid controllers. It’s all done much better in software using erasure coding.
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