EMC Storage Product Knowledge Sharing

Symmetrix Optimizer improves array performance by continuously monitoring access patterns and migrating devices to achieve balance across the disks in the array. This is process is carried out automatically based on user-defined parameters and is completely transparent to end users, hosts and applications in the environment. Migration is performed with constant data availability and consistent protection.

Optimizer performs self-tuning of Symmetrix data configurations from the Symmetrix service processor by:
· Analyzing statistics about Symmetrix logical device activity.
· Determining which logical devices should have their physical locations swapped to enhance Symmetrix performance.
· Swapping logical devices and their data using internal Dynamic Reallocation Volumes (DRVs) to hold customer data while reconfiguring the system (on a device-to-device basis).

Symmetrix Optimizer can be utilized via EMC Symmetrix Management Console or SYMCLI, where user can defines the following:

1) Symmetrix device to be optimized
2) Priority of those devices.
3) Window of time that profiles the business workload.
4) Window of time in which Optimizer is allowed to swap.
5) Additional business rules.
6) The pace of the Symmetrix Optimizer volume copy mechanism.

After being initialized with the user-defined parameters, Symmetrix Optimizer operates totally autonomously on the Symmetrix service processor to perform the following steps.

1) Symmetrix Optimizer builds a database of device activity statistics on the Symmetrix back end.

2) Using the data collected, configuration information and user-defined parameters, the Optimizer algorithm identifies busy and idle devices and their locations on the physical drives. The algorithm tries to minimize average disk service time by balancing I/O activity across physical disk by locating busy devices close to each other on the same disk, and by locating busy devices on faster areas of the disks. This is done by taking into account the speed of the disk, the disk geometry and the actuator speed.

3) Once a solution for load balancing has been developed the next phase to carry out the Symmetrix device swaps. This is don using established EMC Timefinder technology, which maintains data protection and availability. Users can specify if swaps should occur in completely automated fashion or if the user is required to approve Symmetrix device swaps before the action is taken.

4) Once the swap function is complete, Symmetrix Optimizer continues data analysis for the next swap.

How Symmetrix Optimizer works:-

1) Automatically collects logical device activity data, based upon the devices and time window you define.

2) Identifies “hot” and “cold” logical devices, and determines on which physical drives they reside.

3) Compares physical drive performance characteristics, such as spindle speed, head actuator speed, and drive geometry.

4) Determines which logical device swaps would reduce physical drive contention and minimize average disk service times.

5) Using the Optimizer Swap Wizard, swaps logical devices to balance activity across the back end of the Symmetrix array.

Optimizer is designed to run automatically in the background, analyzing performance in the performance time windows you specify and performing swaps in the swap time windows you specify.

From its inception, Symmetrix was designed with the flexibility to incorporate the latest technology in disk drives, memory and other components. This effort has enabled the storage platform to evolve to meet the ever-increasing data demands of enterprises. and has provided customers with unparalleled investment protection. The first-generation Symmetrix 4400 Integrated Cached Disk Array (ICDA), with a total capacity of 24 gigabytes, was introduced in 1990. The seventh-generation system, the Symmetrix DMX-3, was introduced in July 2005 and features a Direct Matrix Architecture® and maximum capacity of one petabyte (1,024 terabytes). The Symmetrix platform has continued to improve and evolve to meet the needs of data-intensive organizations worldwide and remains the most successful intelligent storage platform in history.

With more than 68,000 systems shipped from its introduction in 1990 through the end of June, 2005 and with more than 400 EMC patents covering its technology, Symmetrix remains the high-end storage market leader and continues to set the standard for mission-critical high-end storage innovation.

1990 – Symmetrix 4200 – ICDA (Integrated Cached Disk Array) Technology, Total Capacity 24 GB

1991 – Symmetrix 4200 – 4Mb DRAM, 5.25 HDAs, Mirroring RAID 1

1992 – Symmetrix 4400 - - Dynamic Sparing, RMP Call Home

1993 – Symmetrix 4800 – 16MB DRAM, 1 GB Global Memory,Non-disruptive microcode, Hypervolume Extension.

1994 – Symmetrix 5500-3 – SRDF

1995 – Symmetrix 3.0 Open Symmetrix- FWD SCSI- attach, 3.5’’ HDAs, RAID Protection, SRDF Host Component, Symmetrix Manager

1996 – Symmetrix ESP – Mix CKD/FBA

1997 – Symmetrix 4.0 – TimeFinder, DataReach, InfoMover, Celerra, FDRSOS, Fibre Channel, PowerPath, UltraSCSI, DMSP

1998 – Symmetrix 4.8 – FC-AL/FC-SW, Symmetrix Optimizer

1999 – Symmetrix 5.0 – 333 MHz PPC, 181 GB disks, QoS Controls

2000- Symmetrix 5.5 – 2 GB fibre Channel, 400 MHz PPC

2000-2001 – Symmetrix DMX – Direct Matrix, 500 MHz PPC, 2 GB FC, Back-End Parity RAID

2001 – 2002 – Symmetrix DMX – 2 GB FICON, Gigabit Ethernet SRDF, iSCSI, SRDF/A, TimeFinder/Snap

2003- Symmetrix DMX-2 – 1 Ghz PPC, RAID 5 Data Protection, 32 GB Memory Directors

2003-2004- Symmetrix DMX-2- SRDF Mode Change, Concurrent SRDF, SRDF/Star, TimeFinder/Clone, Open Replicator

2005 – Symmetrix DMX-3 – 8 Processors/Directors, 1.3 GHz PPC, Low Cost FC Disks, Incremental Scalable, Upto 2400 disks, Open Migrator/LM

2005-2006 – Symmetrix DMX-3 – Dynamic Cache Partitioning, Symmetrix Priority Controls, Virtual LUN Technology, Symmetrix Service Credential, Tamper Proof Audit Logs, Secure Data Eraser, RAID 6 Protections.

2007- 2008 Symmetrix DMX-4 – 4GB/s Point to point Backend, FC & SATA Intermix, RSA enVision Intergration, Flash Drives, Virtual Provisioning Cascaded SRDF.

There are two primary ways to reduce power consumption by carefully configuring the storage array itself and by taking advantage of EMC tools. Useful tips that will help to design an efficient DMX-3 array, including:

1) Minimizing DA pairs required.

2) Using more daisy chain storage bays to obtain needed capacity with fewer DA pairs.

3) Fully loading drive enclosures with drives (15) to reduce excess power overhead from cooling, logic, and power supply load efficiency.

4) Fully populating your DA pairs before adding additional pairs.

5) Ordering storage bays in increments of half to fully utilize enclosures.

6) Using larger capacity drives to reduce spindles.

7) Using tiered storage to reduce the number of higher speed drives when requirements allow.

8) Using RAID 5 or other as opposed to RAID 1 full mirroring.

9) Adding incremental storage bays and DA pairs as demand changes.

10) Using shorter loops for high performance drives, longer loops for lower performance drives.

There are other tools and techniques available as well, including:

11) Using Symmetrix Optimizer to balance performance and create opportunities for using larger capacity drives.Using Snaps instead of full volume copies to conserve space and use fewer drives.

Lets talk about SRDF feature in DMX for disaster recovery/remote replication/data migration. In today’s business environment it is imperative to have the necessary equipment and processes in place to meet stringent service-level requirements. Downtime is no longer an option. This means you may need to remotely replicate your business data to ensure availability. Remote data replication is the most challenging of all disaster recovery activities. Without the right solution it can be complex, error prone, labor intensive, and time consuming.

SDRF/S addresses these problems by maintaining real-time data mirrors of specified Symmetrix logical volumes. The implementation is a remote mirror, Symmetrix to Symmetrix.
¨ The most flexible synchronous solution in the industry
¨ Cost effective solution with native GigE connectivity
¨ Proven reliability
¨ Simultaneous operation with SRDF/A, SRDF/DM and/or SRDF/AR in the same system
¨ Dynamic, Non-disruptive mode change between SRDF/S and SRDF/A
¨ Concurrent SRDF/S and SRDF/A operations from the same source device
¨ A powerful component of SRDF/Star, multi-site continuous replication over distance with zero RPO service levels.
¨ Business resumption is now a matter of a systems restart. No transportation, restoration, or restoring from tape is required. And SRDF/S supports any environment that connects to a Symmetrix system – mainframe, open system, NT, AS4000, or Celerra.
¨ ESCON fiber, fiber channel, Gigabit Ethernet, T3, ATM, I/P, and Sonet rings are supported, providing choice and flexibility to meet specific service level requirements. SRDF/S can provide real-time disk mirrors across long distances without application performance degradation, along with reduced communication costs. System consistency is provided by ensuring that all related data volumes are handled identically – a feature unique to EMC. Hope this litte article will help you to understand about SRDF/S.

We have discussed regarding Symmetric DMX-3. Lets talk about Symmetrix Device. DMX-3 system applies a high degree of virtualization between what host sees and the actual disk drives. This device has logical volume address that the host can address. Let me clear that “A symmetrix Device is not a physical disk.” Before actually hosts see the symmetrix device, you need to define path means mapping the devices to Front-end director and then you need to set FA-PORT attribute for specific Host. Let not discuss configuration details now. I am trying to explain what Symmetrix device is if this is not physical disk and how it will be created.

You can create up to four mirrors for each Symmetrix device. The Mirror positions are designed M1, M2, M3 and M4. When we create a device and specify its configuration type, the Symmetrix system maps the device to one or more complete disks or part of disks known as Hyper Volumes/Hypers. As a rule, a device maps to at least two mirror means hypers on two different disks, to maintain multiple copies of data.

I have been posting article related to CLARiiON recently. Lets talk about DMX Series. It is the most popular storage array from EMC. To manage DMX we have tool called ECC ( EMC Control Center, SMC and SYMCLI). Let me first explain what is gatekeeper and what is use?
To perform software operations on the Symmetrix, we use the low level SCSI command. To send SCSI commands to the Symmetrix, we need to open a device. We refer to the device we open as a gatekeeper. Symmetrix gatekeepers provide communication paths into the Symmetrix for external software monitoring and/or controlling the Symmetrix. There is nothing special about a gatekeeper, any host visible device can be used for this purpose. We do not actually write any data on this device, nor do we read any date from this device. It is simply a SCSI target for our special low level SCSI commands. We do perform I/O to these devices and this can interfere with applications using the same device. This is why we always configure small devices (NO data is actually stored) and map them to hosts to be used as "gatekeepers". Solutions Enabler will consider any device with 10 cylinders or less to be the preferred gatekeeper device.

Now you must have understood what is gatekeeper devices. Let me explain more about uses like how many gatekeeper you want to present host so there will be no performance impact.

A general recommendation for the number of gatekeepers for a single host with few applications running is 8. However, a common rule of thumb is a minimum of 6. For a host on which many applications running, 16 is recommended. A gatekeeper should not be mapped/masked to more than one host.
Granular Recommendation (for Solutions Enabler) :
It is hard to recommend an exact number of gatekeepers required for a single host. The number of gatekeeper's required depends on the specific host's configuration and role. This is because it directly relates to performance, therefore it is a subjective number. The following is a recommendation based upon a number of variables pertaining to that specific host. At least 2 gatekeepers for simple Solutions Enabler commands and 1 additional gatekeeper for each daemon or EMC Control Center Agent running on the host.
Granular Recommendation (for Control Center) :
• Two gatekeepers are required when the Storage Agent for Symmetrix is installed on the host, and two (total of four) additional gatekeepers are required when you use Symmetrix Configure commands to manage the Symmetrix system. Each Symmetrix system needs only two Symmetrix agents. The agents need to be installed on separate hosts. This is to provide for
failover when the primary agent goes down for maintenance (or failure).
• Common Mapping Agent and host agents do not require a gatekeeper.
• Note: SYMCLI scripts should not use gatekeepers assigned to ControlCenter; they should have their own.

Gatekeepers are typically 6 cylinders or 2888 KB in Size. All gatekeeper type devices should be protected by either RAID-1 or RAID-S.
Hope this will help you in deciding number of gatekeeper to assign the host.Because it is matter of performance.

Most of time you end up thinking that we had 500 GB disk but it finish without utlizing full capacity. Answer for this that whatever size you buy you do not get full amount of size becuase DMX size calculation on cylinder basis. Lets understand how DMX calculation size of disk:

1) How DMX 2 and Symmetrix Covert cylinder to GB?
GB = Cylinders * 15 * 64 * 512 divided by 1024 * 1024 * 1024
for example 18570 cylinders is 8.5 GB

2) How DMX 2 and Symmetrix Covert GB to cylinder?
Cylinders = GB / 15 / 64 / 512 then multiply result by 1024*1024*1024

3) How much capacity do I get from a drive ?
This depends on the drive and splits required.
For example a 73GB drive with 8 splits gives 8 x 18570 cyl volumes = 68 GB.

4) How DMX 3 Covert cylinder to GB?
GB = Cylinders * 15 * 128 * 512 divided by 1024 * 1024 * 1024
for example 18570 cylinders is 17,00 GB

5) How DMX 2 and Symmetrix Covert GB to cylinder?
Cylinders = GB / 15 / 128 / 512 then multiply result by 1024*1024*1024

6) How much capacity do I get from a drive ?
This depends on the drive and splits required.
For example a 73GB drive with 4 splits gives 4 x 18570cyl volumes = 68 GB.

Now, you must have understand the formula of calcuating the actual size of disk you can use on any symmetrix or DMX.