3hub virus2/20/2023 ![]() Hardware RAID can be really good for speed but it does not provide the consistency guarantees of something like ZFS. Innovation is always going to favor openness, but alas it’s rare for hardware to be open □ New drives could be added and even raid level could be changes and while maintaining data integrity. The raid controller could use programmable descriptor tables to know where to load/save data to including redundancy. But if we had the ability to program the hardware raid we really could have the best of both worlds. Dynamic raid is not intrinsically limited to software, but the problem is that hardware raids tend to be closed/proprietary such that we can’t do much more with them out of the box. It would even be possible to have some data protected by raid-1 and other data use raid-0 or raid-6 without having to define static partitions for them.īoth hardware raid and software raids have advantages over the other, and it makes me wish we could have both. ![]() Those are cons compared to being able to add and remove drives to the set willy-nilly and have the system automatically redistribute data while maintaining raid redundancy, which more sophisticated raid software can handle. They 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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