Any #ZFS folks want to offer me an opinion on the following? I have 2 ZFS pool of raidz2 with 7 2TB SAS drives each (about 11.5T). I want to add a LOG drive. I have a single SAS SSD that's 300G. When I suggested using a 1TB LOG drive earlier, someone said that was way too much. (which is why I picked up a used 300G SSD)
My question is whether it makes sense (is possible) to partition that drive into 2 partitions and have one pool use 1 partition as a log drive (e.g., 150G) and the other pool use the other partition as a log drive on the same physical device.
Is this going to be worse because it's just too much IO on one device? Is it reasonable? Any other ideas?
feld
in reply to Paco Hope wishes ill for JK Rowling • • •oh gosh, unless you know you are doing a lot of synchronous writes (almost never; databases and NFS mostly... maybe VMs???) you do not need a LOG at all.
If you do add a LOG, it just needs to be large enough to buffer the writes until they're flushed to the other vdevs. You honestly could get away with something as small as like 8GB for a low IO / homelab type environment. But you won't find a modern drive that small, so if you're going to do this just make it as small as possible. Pick quality over quantity here. SLC drives (do they even exist anymore?) are of course ideal.
Splitting the LOG device between multiple zpools isn't crazy. I have a tiny partition I use for LOG and then use the rest for L2 ARC which is another option to maximize the usage of your fast storage.