Enable auto tune... yes or no?

[hugovsky]

I'm running freenas 9.3-beta with recent update installed on a 8GB usb drive. I have 16 ECC ram running on a A1SAi-2750F. RAIDZ2 with 4 reds 1TB each. Do you think I should enable autotune? I'm using the nas at home. CIFS, AFP and unix shares but no real load. What's the best tests I can use to determine perfomance? I can destroy the pool I'm using if needed to test. My basic question is to know if I should at least try it or not.

 

[Norleif]

One tuning option that isn't in "auto tuning" would be to change your 4-drive RAIDZ2 to striped mirrors...

 

[hugovsky]

damn... so simple... shame on me... my read speeds went up by 4x+ and my write almost 3x. Thanks for the tip. About my question, no autotune needed? I've read here that autotune should be used only in 16GB+ ram systems.

 

[Fraoch]

I've read here that autotune should be used only in 16GB+ ram systems.

Ouch, would you mind posting where you found that?

I'm using autotune. I haven't experienced problems but I was not aware you needed more than 16 GB of RAM in order to use it.

 

[hugovsky]

Here. But it may be off because it's a diferent freenas version and more than a year old post.

this is my pool now:

Code:

pool: tank

state: ONLINE
  scan: none requested
config:

        NAME                                                STATE     READ WRITE CKSUM
        tank                                                ONLINE       0     0     0
          mirror-0                                          ONLINE       0     0     0
            gptid/0859fde3-6c1d-11e4-949f-002590f52106.eli  ONLINE       0     0     0
            gptid/0999d18d-6c1d-11e4-949f-002590f52106.eli  ONLINE       0     0     0
          mirror-1                                          ONLINE       0     0     0
            gptid/0b4beb5b-6c1d-11e4-949f-002590f52106.eli  ONLINE       0     0     0
            gptid/0c4aa1f1-6c1d-11e4-949f-002590f52106.eli  ONLINE       0     0     0

But now I can't have 2 drives failing at the same time like raidz2, right? Or can I?...

 

[RobertT]

two drives in one mirror could fail but if one drive in each mirror fails you are hosed.

 

[mjws00]

Autotune is pretty much deprecated, and only useful in a few scenarios. See cyberjocks explanation.

 

[hugovsky]

So, the answer is a big no. Thanks for clarifying.

 

[hugovsky]

two drives in one mirror could fail but if one drive in each mirror fails you are hosed.

In RAIDZ2, any 2 of 4 can fail. In this config, you are saying that I can loose 2 drives in mirror-0 without issues but can't loose 1 drive in mirror-0 and 1 drive in mirror-1?

 

[mjws00]

No. Each mirrored pair is a vdev. All vdevs must be present. You can lose one drive from each pair and still have sufficient replications of your data for a healthy pool. Mirrors resilver faster and have more iop potential. Raidz2 allows that extra drive to fail that would hurt you in a mirrored solution. Both are safe, mirrors are best practice for performance.

 

[gpsguy]

RobertT has it backwards. You can't loose 2 disks in a mirror (vdev) without loosing your pool. You could loose one disk in each of the mirrors without loss.


Sent from my phone

 

[hugovsky]

Well, I have backups of important data on this nas. I guess it own't hurt trying a mirror volume this time. Maybe I'll get another red and then rebuild with raidz2.