1 © Copyright 2008 EMC Corporation. All rights reserved. Symmetrix Capacity Planning and Performance Aspects Bob Rau Technical Business Consultant Symmetrix Champion, SPEED, CSPEED EMC Corporation

2 © Copyright 2008 EMC Corporation. All rights reserved. Topics Capacity Planning (from the Symmetrix side)  Disk drives  How fast?  How big?  How much work do they do?  Utilization  Front-end ports  Or is it CPUs? Or boards?  How about the back-end? Performance Aspects (from the Symmetrix side)  Almost everything counts  But a few things don’t! Performance Aspects (from the server side)  Tuning your server to match your storage

3 © Copyright 2008 EMC Corporation. All rights reserved. Capacity Planning – Disk Drives How Fast?  15K  Around 50% more cost  About 30% more work  If you have to have that 30% you have to have 15K drives  10K  Pretty darn good  Cache memory can mask the slower speed from the host (sometimes)  7.2K  Slower?  Some workloads will thrive on these drives  Flash Drives (SSD)  Faster than a speeding bullet, able to leap over tall buildings, but….  You probably can’t afford too many  You need to manage them carefully  You need the right type of workload

4 © Copyright 2008 EMC Corporation. All rights reserved. Capacity Planning – Disk Drives How Big?  The size of the drive doesn’t matter (usually)  Within the same speed most capacities perform the same  10K: 73 GB, 146 GB, and 300 GB are all the same  400 GB drives are a little better  15K: 73 GB, 146 GB are all the same  300 GB drives are a little better  7.2K: all of the SATA II drives are the same  Flash Drives: 73 GB and 146 GB are the same  So the actual important question is: How much work can they do?

5 © Copyright 2008 EMC Corporation. All rights reserved. Capacity Planning – Disk Drives How much work can they do?  The important measure is “SCSI commands/second”  This includes all of the things disk drives do including  Reading  Writing  Moving the heads  Housekeeping  Parity calculations  Etc. FD15K10K7.2K 5, Drive type SCSI commands/sec (if you are really good) 5, SCSI commands/sec (plan on these numbers) Be careful…. This is at 100% utilization! DMX arrays only

6 © Copyright 2008 EMC Corporation. All rights reserved. Capacity Planning – Disk Drives What about % utilization?  With a brand new Symmetrix EMC likes to target 35% to 40% disk drive utilization  When utilization goes above 70% performance can become erratic  With certain workloads (like backups) there is nothing wrong with 100% utilization < 30%50%70% x2x3x Utilization Disk drive response time

7 © Copyright 2008 EMC Corporation. All rights reserved. Capacity Planning – Front-End Ports What’s the most important part of the front-end??  Front-end boards almost never matter  Front-end ports are very important  Workload on the port  Ensuring high availability  Restrictions on fan-in and fan-out  Restrictions on LUN counts  Front-end CPUs are the truly controlling factor

8 © Copyright 2008 EMC Corporation. All rights reserved. Capacity Planning – Back-End Boards Most of the time back-end boards are not a factor – except…  When there is a lot of remote replication workload  When there is a lot of Raid-6  When the loops get above 45 devices  When you are configuring Flash Drives

9 © Copyright 2008 EMC Corporation. All rights reserved. Performance Aspects – from the Symmetrix Utilization numbers are always important  Utilization numbers above 70% cause erratic and poor performance  Modern storage arrays are designed to ride through brief performance spikes  One or two minute spikes are brief  15 minute spikes are forever!  Always remember – if you plan a workload for 70% utilization numbers you are already at the ceiling

10 © Copyright 2008 EMC Corporation. All rights reserved. Performance Aspects – from the Symmetrix I/Os per second –vs- MBs per second  These are natural enemies!  You can do more I/Os if each one is small  You can move more data if each I/O is big

11 © Copyright 2008 EMC Corporation. All rights reserved. Performance Aspects – from the Symmetrix Important performance stuff that doesn’t matter  Read / Write ratio  Cache hit ratio Okay – I lied. It does matter but you can’t do anything about it!

12 © Copyright 2008 EMC Corporation. All rights reserved. Performance Aspects – from the Symmetrix Raid protection choices  Raid-1 – far less than in the past  Raid-5 – far more than in the past  Split about 50/50 between 3+1 and 7+1  Performance is usually equal – choose based on rebuild time  Raid-6 – becoming very popular for large capacity drives  Much less often on smaller drives  Watch the performance of the DA processors  As of 5772 code you can intermix all Raid types in one array  Flash Drives only support Raid-5

13 © Copyright 2008 EMC Corporation. All rights reserved. Performance Aspects – from the Symmetrix It’s time to embrace tiering  There are lots of ways to do tiering  Drive speed appears to be the best choice  Then pick the drive capacities necessary to support the expected workload  Virtual LUN Migrator  Included with Symmetrix Optimizer as of 5772 code  Moves LUNs within an array  Target can be equal or larger  Raid protection can be changed during the migration (5773 code)  Non-disruptive  Groups of moves can be defined  Did I mention that the move is non-disruptive?  What to move where?

14 © Copyright 2008 EMC Corporation. All rights reserved. Performance Aspects – from the Symmetrix Flash Drive targets? SATA II targets? 2

15 © Copyright 2008 EMC Corporation. All rights reserved. Performance Aspects – from the Symmetrix Pay attention to Virtual Provisioning  Virtual Provisioning (Thin Provisioning) arrived in 5773 code  EMC did it right  In almost all of the customer environments EMC tested the results were the same  Virtual Provisioning wins in performance  This is the ultimate way to spread your data “wide”  VP is much easier to manage  VP is must faster to provision  VP is much better at capacity utilization  VP lets you allocate whatever amount you want.

16 © Copyright 2008 EMC Corporation. All rights reserved. Performance Aspects – from the Symmetrix You have to monitor a Symmetrix  The problem is kind of strange  A Symmetrix is powerful enough to hide your sins… … until it reaches some limit and then you’ve got a problem!  Let WLA publish to an internal website – but don’t publish too much  Set thresholds to deliver the message clearly

17 © Copyright 2008 EMC Corporation. All rights reserved. Performance Aspects – from the Symmetrix Use Optimizer to keep the disk utilization balanced  As arrays get larger and larger Optimizer becomes more important  As disk drives become larger and larger disk seeking becomes a bigger problem  Monitor “seek distance per second”  Moving the heads is honest work for a disk drive but it isn’t very productive

18 © Copyright 2008 EMC Corporation. All rights reserved. Performance Aspects – from the Server Make your servers happy  Use channel load balancing software – always!  Please…. Watch your Queue Depth settings  HBA driver defaults of “8” just aren’t large enough  If you are using an eight-way metavolume from a server with two HBAs that can see the meta, then the correct setting is 32.  The formula: 8 * n / h = Queue Depth setting where n = number of members in the biggest metavolume where h = number of HBAs that can see the metavolume