SATA 7500RPM performance

[stresnik]

I just installed a 24 disk SATA shelf.  I was unaware we ordered 7500RPM SATA disks.  Our other shelves are SAS and FC at 15000RPM and 10000RPM respectively.  I created a new aggregate for the SATA disks as to not mix them.  However I am concerned how well these disks will perorm.  I had planned on using them for Exchange 2013 databases as well as storage for the system drives for Hyper-V servers.  Should I be concerned?  

This shelf is on an FAS3240 with OnTap8.2.2 7-mode

thanks

[ekashpureff]

Stresnik -

I'd be concerned if I didn't know the IO density of the applications running on the storage.

Flash cache can make a significant difference for you though.

The IO density of SATA drives is much lower than that of SAS drives.

The factors that account for it are max random IOs per drive, and size of the drive.

A 600 GB SAS drives will do ~175 random IOs, and has a usable capacity of ~500G.

The IO density is 2 X 175 IOs, or about 350IOs/TB.

A 2TB SATA drive will do ~75 random IOs, and has a usable capacity of ~1.5TB.

The IO density is .66 X 75 IOs, or about 50IOs/TB.

Best practice is to monitor aggregate performance, and the IO performance of the applications storage is provisioned for.

I hope this response has been helpful to you.

At your service,

Eugene E. Kashpureff, Sr.
Independent NetApp Consultant http://www.linkedin.com/in/eugenekashpureff
Senior NetApp Instructor, IT Learning Solutions http://sg.itls.asia/netapp
(P.S. I appreciate 'kudos' on any helpful posts.)

[stresnik]

Thanks ekashpureff,

I have the 2TB SATA disk you site in your example.  I wish I had the luxury of time to test the performance.  Thanks again.

[Stefan-Reitmeier]

Sata Disk should be fine for Exchange 2013 and some low end VM's. You should be careful for OS partition on slow storage with Windows servers as slow OS partition can affect system and application performance.

Also carefully test deduplication, compression, snapshots and snapmirror as they all produce additional internal io. 

With flashcache cards you should be fine, as they make a hugh difference with slow drives on NetApp. Random reads do really hurt sata drives.

Especially as your io budget with 24 sata drives is not that high.

[hariprak]

Hi,

When the SAS and SATA disks are owned by the same controller, it is most likely, when doing writes the NVRAM is shared and the slower SATA disks will affect the entire controller performance.

Thanks

[stresnik]

Can someone confirm what Hariprak says about mixed disk will slow everything on that controller?  If this is true, this is worse than I thought, which is it will only slow any aggregate with mixed disks.

[RPHELANIN]

what Hariprak is saying is correct. Ideally SAS and SATA should not be mixed on the same controller but this is not always acheiveable. When data hits the controller it is sorted in RAM \ NVRAM by aggregate (chain) and then flushed to each aggregate at the same time (consistency point). If the SATA aggregate (or the SAS aggregate) cannot stripe to all the disks before NVRAM fills up again (or within 10 seconds) you will have performance issues (back to back consistency points). You could try and move some low IOPs data to the new SATA aggregate (CIFS is generally low IO)