NetApp E5460 Mix Disk Layout

[SZBJH6_HT]

Hi,

We recently purchased Netapp E5460 running on Santricity 10.86 with 30x 900GB SAS 10krpm, 10x2000GB NL-SAS 7.2Krpm and 4x900 SSDs. The suggestion is to layout the disks as follows so that it can optimise drawer loss protection:

Drawer 1 - consists of 1x900 SSD, 2x2000NL-SAS, and 6x900GB SAS  (left to right starting from the first row)

Drawer 2 - consists of 1x900 SSD, 2x2000NL-SAS, and 6x900GB SAS (left to right starting from the first row)

Drawer 3 - consists of 1x900 SSD, 2x2000NL-SAS, and 6x900GB SAS (left to right starting from the first row)

Drawer 4 - consists of 1x900 SSD, 2x2000NL-SAS, and 6x900GB SAS (left to right starting from the first row)

Drawer 5 - consists of 2x2000NL-SAS, and 6x900GB SAS (left to right starting from the first row)

However, the engineer who is installing the Netapp is suggesting that all drives of the same type should be on the same drawer because of performance issues. If that is the case, the layout would be as follows:

Drawer 1 - consists of 4 x 900GB SSD (left to right starting from the first row)

Drawer 2 - consist of 10 x 900GB SAS (left to right starting from the first row)

Drawer 3 - consists of 10 x 900GB SAS (left to right starting from the first row)

Drawer 4 - consists of 10 x 900 GB SAS (left to right starting from the first row)

Drawer 5 - consists of 10 x 2000 GB NL-SA (left to right starting from the first row)

I have been browsing the Netapp website and other Netapp documents on E5460 but cannot find any explanation on best practice on mix drives layout on E series.

Comments are appreciated.

Regards

H Tina

[jlatham]

Tina,

Not sure what/why they would recommend putting all drives on one type on a single shelf for performance.

I would mix it up as you describe in the top of the message.

This would spread the SSD's,and the other drives, across more/separate SAS lanes (in a give array) avoiding any potential bottlenecks.

It would also enable "tray loss protection" if configured with appropriate RAID arrays.

Also note that there has been extensive engineering effort put into the enclosure to dampen drive vibration so that the mixing of different rotational speed drives on the same tray/in same enclosure does not have a detrimental effect.

Hope it helps.

Jim

[SZBJH6_HT]

Hi Jim,

Thanks for your comments.

1) I'm not privy to NetApp E5460 algorithm on how disks are accessed on different drawers, but if I follow the same analogy of "stripe width and segment size", I would like to think that there is performance hit to "jump disks from drawer to another drawer" rather than "jump disk within the same drawer".

If there is a "performance degrading segment crossing", you would like to think that there is also a "performance degrading drawer crossing".

Thus in the disk layout in example 1 above where I have 30x900GB SAS drives distributed evenly on 5 drawers, this would be more "performance hit" as compared with disk layout in example 2 where 30x900GB drives are distributed on 3 drawers.

You also mentioned about different rotational speed of drives on the same tray/drawer if different types of drives are mixed in the same drawer and again, I'm not sure about the performance implication of this setup.

Without knowing how E5460 algorithm and E5460 hardware (eg SAS lane, controller, etc)  works, I can only speculate.

Maybe somebody from the NetApp E Series (or LSI Engenio)  design team can comment on the above.

Regards

H Tina

[tschmitz]

Hi Tina,

Striping across drawers within a Wembley is the best practice.  We have also achieved our performance numbers with within Wembley striping. 

I see a 3+1 for SSD’s, 8+2 for 2TB drives, and 3 (8+2) groups for 10K drives. 

Based on that configuration you have an optimum configuration from a reliability, availability, and performance perspective.  

TS