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First ZFS don't need much RAM, you are fint with as little as 2GB. You can still use hardware raid with ZFS if you export each disk as its own device and assem
by olavgg 9y ago
First ZFS don't need much RAM, you are fint with as little as 2GB.
You can still use hardware raid with ZFS if you export each disk as its own device and assemble the raid with ZFS. It is not the parity calculations that are slow, it is the additional io operations that are required and ZFS writes these directly to disk. A hardware raid controller writes these io operations to memory. Another advantage with ZFS is if your data compress well, you will get additional speed benefit from that.
- frozenport 9y agoFrankly, I suspect the ZFS community is in denial, or optimizing for cost. I got what I think is a correctly configured ZFS system and its getting the same speeds as most people report online. NOW the thing is that the ZFS system doing about 2x worse for the dense sequential write workloads compared to the RAID6 HW solution. Not to mention eating a dozen or so GBs of RAM.
- olavgg 9y agoZFS autotunes memory allocation based on how much ram you have, if you have 128GB ram free, ZFS will use that. In fact all operating systems eat GB's of free RAM just like ZFS. Software raid has a larger write penalty, that is why you see slower write performance versus using hardware raid. As I said earlier, writing directly to memory helps. Recommended read: http://rickardnobel.se/raid-5-write-penalty/ http://rickardnobel.se/raid-5-write-penalty/
- frozenport 9y agoSo, basically, if you're building a $15,000 storage box, cough up $500 for a hardware RAID solution.