Hello all, I'm seeing a huge discrepancy between my read/write speeds over the network, my unraid box is a simple celeron 2.2ghz with 2GB RAM, 3x 1.0TB WD  Green GP drives 5400rpm (with parity enabled), and an intel pro 1000 PT dual port gig-e card, connected to a Dlink Green gig switch, connected to my PC which is a 2.6 core 2 duo, 8 gb ram, intel pro 1000 PT gig-e...  Reading from the unraid box, I can get upto 70 MB/s sustained, but writing back I can barely get over 12 MB/s... I am assuming this is because of unraid calculating the parity of the new files.. so will a cpu/ram upgrade really help?  If I do upgrade the cpu/ram, do I have to reinstall unraid on my flash drive or will it automagically work?

That's about right. Each write take 4 IOs, 2 reads and 2 writes. ~15 is the max speed you'll get.

Hello all, I'm seeing a huge discrepancy between my read/write speeds over the network, my unraid box is a simple celeron 2.2ghz with 2GB RAM, 3x 1.0TB WD  Green GP drives 5400rpm (with parity enabled), and an intel pro 1000 PT dual port gig-e card, connected to a Dlink Green gig switch, connected to my PC which is a 2.6 core 2 duo, 8 gb ram, intel pro 1000 PT gig-e...  Reading from the unraid box, I can get upto 70 MB/s sustained, but writing back I can barely get over 12 MB/s... I am assuming this is because of unraid calculating the parity of the new files.. so will a cpu/ram upgrade really help?  If I do upgrade the cpu/ram, do I have to reinstall unraid on my flash drive or will it automagically work?

 

CPU and Ram will not help here.  The one thing that will is using the cache drive that is available in the Pro version of unRAID.

Hello all, I'm seeing a huge discrepancy between my read/write speeds over the network, my unraid box is a simple celeron 2.2ghz with 2GB RAM, 3x 1.0TB WD  Green GP drives 5400rpm (with parity enabled), and an intel pro 1000 PT dual port gig-e card, connected to a Dlink Green gig switch, connected to my PC which is a 2.6 core 2 duo, 8 gb ram, intel pro 1000 PT gig-e...  Reading from the unraid box, I can get upto 70 MB/s sustained, but writing back I can barely get over 12 MB/s... I am assuming this is because of unraid calculating the parity of the new files.. so will a cpu/ram upgrade really help?  If I do upgrade the cpu/ram, do I have to reinstall unraid on my flash drive or will it automagically work?

The CPU and RAM have very little to do with the difference in speed in reading vs. writing.   But, if you do upgrade them, you do not need to do anything for unRAID to recognize them.  (You do need to set the appropriate RAM voltage, timing, and clock speed on many motherboards... They frequently get it wrong or use very conservative values.  In the case of voltage, high-speed-premium RAM often requires higher voltage settings.  If not set properly, you will get lots of random errors and system crashes.)

 

For the most part, the CPU is idle most of the time... It is almost entirely waiting for the disks to spin.  Remember, at best case when writing to a disk, after first reading the parity and data disk, and then calculating parity with the new data to be written, in order for the same sectors of those two disks to be updated in a "write" operation, those sectors MUST rotate to be under the disk heads once more.   Best case is if it can be done with only a single rotation of the disk.  If not, it must wait another full rotation before writing. 7200 RPM disks will do better than slower disks.

 

You can speed up your "write" speed by using disks with higher rotation speed, and higher speed PCIx buses, and splitting the load across different disk controllers and buses (if possible)

 

The use of the "cache" drive in the PRO version of unRAID will make it seem as if writing is faster fro your PC, but does not get rid of the time it takes to write to the disks in the protected array, it just allows an initial unprotected (but faster) write to a cache disk.   It is faster only because it has only one I/O operation, and your data is not initially protected by parity.    Later, usually in the middle of the night, the data is moved (written) to the protected array and all the I/O occurs while you sleep.

 

Joe L.