Mix of AF and nonAF drives in new build

[ednigma]

I've been away from unRaid for a while and want to build an new array.  I have a 2 Hitachi 1.5T drives, one is 7200rpm and the other is Coolspin (5400?). and I just purchased a Seagate ST1500DL003 1.5T spinning at 5900rpm that I understand is an AF drive (Seagate SmartAlign?). 

 

Which should be my parity drive - I was thinking the Hitachi 7200rpm.  But I've since read that AF drives may perform better but is this true for the parity function?  Will the Hitachi 7200rpm still perform better vs the 5900rpm AF?

 

Do I format each drive 4k aligned or only the Seagate?

 

When preclearing, do I have to specify the alignment or is this only selected at the time of formatting.

 

Thanks

Ed

[Joe L.]

I've been away from unRaid for a while and want to build an new array.  I have a 2 Hitachi 1.5T drives, one is 7200rpm and the other is Coolspin (5400?). and I just purchased a Seagate ST1500DL003 1.5T spinning at 5900rpm that I understand is an AF drive (Seagate SmartAlign?). 

There is only one drive we know of that performs poorly when not 4k aligned  (The WD EARS drive).    All drives will work perfectly when 4k aligned EXCEPT one drive (that same WD EARS drive when a hardware jumper has been added to it)

 

Therefore, unless you have a WD EARS drive, you can set the unRAID option in settings to MBR-4k-aligned and leave it there and forget about it going forward.

Which should be my parity drive - I was thinking the Hitachi 7200rpm.  But I've since read that AF drives may perform better but is this true for the parity function?

Writes to the unRAID array are limited by the rotational speed of the slowest drive involved.  Unless you are writing concurrently to multiple data drives, a faster rotating parity drive will not speed things up.  If any other data drive is 7200 RPM (or might be in the future), the parity drive should also be 7200 RPM to get the best speed when writing that 7200 RPM data drive.

  Will the Hitachi 7200rpm still perform better vs the 5900rpm AF?

Yes. It spins 1/3 faster, so you can read and subsequently write the same sector faster.

Do I format each drive 4k aligned or only the Seagate?

All drives can be set to MBR-4k aligned. (unless you own a WD EARS drive)

When preclearing, do I have to specify the alignment or is this only selected at the time of formatting.

If you do not specify the alignment, the preclear script will use the setting you elected in the unRAID settings.

(The preclear option of -A = 4k aligned, -a = 4k-unaligned )

Thanks

Ed

You are welcome.  I would use the 7200 RPM drive for parity as it seems manufacturers are producing more of them these days, and future  additions to your array are likely to be faster spinning drives.

 

Joe L.

[ednigma]

Thanks a bunch Joe!

 

How did I know that you would answer and answer so clearly?

 

I guess I was confused by reading something about AF drives performing better when aligned, but now that I read that passage again in light of your answer, it was specifically pertaining to the WD EARS drive and not to AF drives in general.

 

Regards..

Ed