RAIDZ1 slow read speeds, writes are fine

[stealth915]

Hi, I don't know if this belongs in here or Newbie questions, but I am wondering if anyone can help me figure out why my RAIDZ1 array is so slow - particularly reads. My reads max out at around 30MB/s when I'm not doing anything else. If I'm downloading to it at the same time, the read speeds drop down to the 15-20MB/s range. Strangely, I don't seem to have any problems writing, as my write speeds are consistently around 55MB/s.

My hardware is:
MSI E-350IA-E45 Mini-ITX Motherboard
8GB RAM
RAIDZ1 with 5x2TB drives
- 2x Samsung Ecogreen F4
- 1x Western Digital RED
- 1x Western Digital Green (WD20EARS)
- 1x Seagate Barracuda Green

I also have another drive that I'm running Nas4Free (full install) from.

Since my motherboard only has 4 SATA ports, I bought a Rosewill RC-216 card to accommodate all the drives.

I've used installed and used ZFS Kernel Tune for 8GB RAM and disable prefetch. I've run a few scrubs and they all say "no known data errors". All the disks are configured to Level 254-Maximum Performance and Disabled acoustic level.

I'm pretty new to Nas4Free so I was wondering where I would begin to troubleshoot this problem. Any tips would be greatly appreciated! Thanks!

[rostreich]

enable prefetch in zfskerntune! this should be the main handbrake!

Level 254-Maximum Performance

switch this to disabled as you already want max performance!

such different disks aren't optimal, also. but your write speed is just perfect, so the different disks are not the problem.

[stealth915]

Thanks! I disabled the power management and enabled prefetch in ZFS Kerntune, and now I'm getting about 40MB/s reads.

It's still slower than my write speed though - is there anything else I can try to make it faster?

[Ouroborus]

I had similar issues. My writes where stable 100MB+ but the reads went crazy and bursty. I had to disable aio in smb settings. Too bad i don't get constant 100+ reads also. Now the all over speeds are lower but stable. Any suggestions?