@T_Minus my working dataset IS sync=always because I am using NFS for my VMware datastores. I ran 3 VM's each on a seperate host of my 3 node vSphere cluster totaling 180GB of data so I KNOW I am WAY outside of my memory bounds (ARC cache) and no L2ARC in the mix. I DID try FreeNAS iSCSI volumes and forcing sync=always and that did indeed force synchronous writes to the SLOG in that mode (you can see it live by turning sync on and off during sVMotion on that iSCSI zvol) whereas by default iSCSI will go async and you will see NO SLOG usage. What I love about NFS really, SLOG is nearly the perfect use case for VMware/Virtualization on NFS.
What is odd and I can't seem to wrap my damn head arnd is this...had two more HUSMM 200GB SAS3 drives show up today, new SLOG dev's, tried to add to my 4 device HUSMM 400GB devices raidz pool in stripe SLOG mode and immediately saw writes evenly distributed to each SLOG device but the overall throughput to the SLOG whether 1 device or two was equal (about 200MB/sec). Creepy to see 1 dev happily soaking in 200MB, think your gonna add another stripe SLOG in and watch log performance double and each dev drops to 1/2 of what one dev was doing...TOTALLY a wtf moment.
EDIT: I gotta say, while the P3700 is the SLOG king IMHO for what I could get my grubby hands on a 400GB P3700 is not cheap and w/ a $80-100 200GB HUSMM sas3 device providing 200MB SLOG write throughput v.s. 300MB for a P3700 the cost difference is staggering for the bang for buck you get (or don't).
2cents, here's to hoping that Intel Optane DC P4800X test is out of this world, anyone else tested one of those yet as SLOG w/ a similar setup/config/use case?
What is odd and I can't seem to wrap my damn head arnd is this...had two more HUSMM 200GB SAS3 drives show up today, new SLOG dev's, tried to add to my 4 device HUSMM 400GB devices raidz pool in stripe SLOG mode and immediately saw writes evenly distributed to each SLOG device but the overall throughput to the SLOG whether 1 device or two was equal (about 200MB/sec). Creepy to see 1 dev happily soaking in 200MB, think your gonna add another stripe SLOG in and watch log performance double and each dev drops to 1/2 of what one dev was doing...TOTALLY a wtf moment.
EDIT: I gotta say, while the P3700 is the SLOG king IMHO for what I could get my grubby hands on a 400GB P3700 is not cheap and w/ a $80-100 200GB HUSMM sas3 device providing 200MB SLOG write throughput v.s. 300MB for a P3700 the cost difference is staggering for the bang for buck you get (or don't).
2cents, here's to hoping that Intel Optane DC P4800X test is out of this world, anyone else tested one of those yet as SLOG w/ a similar setup/config/use case?
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