Continuing my week in Chicago, for the IBM Storage Symposium 2008, I attended two presentations on XIV.

XIV Storage - Best Practices

Izhar Sharon, IBM Technical Sales Specialist for XIV, presented best practices using XIV in various environments.He started out explaining the innovative XIV architecture: a SATA-based disk system from IBM can outperformFC-based disk systems from other vendors using massive parallelism. He used a sports analogy:

"The men's world record for running 800 meters was set in 1997 by Wilson Kipketer of Denmark in a time of 1:41.11.

However, if you have eight men running, 100 meters each, they will all cross the finish line in about 10 seconds."

Since XIV is already self-tuning, what kind of best practices are left to present? Izhar presented best practicesfor software, hosts, switches and storage virtualization products that attach to the XIV. Here's some quickpoints:

Use as many paths as possible.

IBM does not require you to purchase and install multipathing software as other competitors might. Instead, theXIV relies on multipathing capabilities inherent to each operating system.For multipathing preference, choose Round-Robin, which is now available onAIX and VMware vSphere 4.0, for example. Otherwise, fixed-path is preferred over most-recently-used (MRU).

Encourage parallel I/O requests.

XIV architecture does not subscribe to the outdated notion of a "global cache". Instead, the cache is distributed across the modules, to reduce performance bottlenecks. Each HBA on the XIV can handle about 1400requests. If you have fewer than 1400 hosts attached to the XIV, you can further increase parallel I/O requests by specifying a large queue depth in the host bus adapter (HBA).An HBA queue depth of 64 is a good start. Additional settings mightbe required in the BIOS, operating system or application for multiple threads and processes.

For sequential workloads, select host stripe size less than 1MB. For random, select host stripe size larger than 1MB. Set rr_min_io between ten(10) and the queue depth(typically 64), setting it to half of the queue depth is a good starting point.

If you have long-running batch jobs, consider breaking them up into smaller steps and run in parallel.

Define fewer, larger LUNs

Generally, you no longer need to define many small LUNs, a practice that was often required on traditionaldisk systems. This means that you can now define just 1 or 2 LUNs per application, and greatly simplifymanagement. If your application must have multiple LUNs in order to do multiple threads or concurrent I/O requests, then, by all means, define multiple LUNs.

Modern Data Base Management Systems (DBMS) like DB2 and Oracle already parallelize their I/O requests, sothere is no need for host-based striping across many logical volumes. XIV already stripes the data for you.If you use Oracle Automated Storage Management (ASM), use 8MB to 16MB extent sizes for optimal performance.

For those virtualizing XIV with SAN Volume Controller (SVC), define manage disks as 1632GB LUNs, in multiple of six LUNs per managed disk group (MDG), to balance across the six interface modules. Define SVC extent size to 1GB.

XIV is ideal for VMware. Create big LUNs for your VMFS that you can access via FCP or iSCSI.

Organize data to simplify Snapshots.

You no longer need to separate logs from databases for performance reasons. However, for some backup productslike IBM Tivoli Storage Manager (TSM) for Advanced Copy Services (ACS), you might want to keep them separatefor snapshot reasons. Gernally, putting all data for an application on one big LUNgreatly simplifies administration and snapshot processing, without losing performance.If you define multiple LUNs for an application, simply put them into the same "consistencygroup" so that they are all snapshot together.

OS boot image disks can be snapshot before applying any patches, updates or application software, so that ifthere are any problems, you can reboot to the previous image.

Employ sizing tools to plan for capacity and performance.

The SAP Quicksizer tool can be used for new SAP deployments, employing either the user-based orthroughput-based sizing model approach. The result is in mythical unit called "SAPS", which represents0.4 IOPS for ERP/OLTP workloads, and 0.6 IOPS for BI/BW and OLAP workloads.

If you already have SAP or other applications running, use actual I/O measurements. IBM Business Partners and field technical sales specialists have an updated version of Disk Magic that can help size XIV configurations fromPERFMON and iostat figures.

XIV Performance

Lee La Frese, IBM STSM for Enteprise Storage Performance Engineering, presented internal lab test results forthe XIV under various workloads, based on the latest hardware/software levels [announced two weeks ago]. Three workloadswere tested:

• Web 2.0 (80/20/40) - 80 percent READ, 20 percent WRITE, 40 percent cache hits for READ.YouTube, FlickR, and the growing list at [GoWeb20] are applications with heavy read activity, but because of[long-tail effects], may not be as cache friendly.

• Social Networking (50/50/50) - 50 percent READ, 50 percent WRITE, 50 percent cache hits for READ.Lotus Connections, Microsoft Sharepoint, and many other [social networking] usage are more write intensive.

• Database (70/30/50) - 70 percent READ, 30 percent WRITE, 50 percent cache hits for READ.The traditional workload characteristics for most business applications, especially databases like DB2 andOracle on Linux, UNIX and Windows servers.

The results were quite impressive. There was more than enough performance for tier 2 application workloads,and most tier 1 applications. The performance was nearly linear from the smallest 6-module to the largest 15-module configuration. Some key points:

• A full 15-module XIV overwhelms a single SVC 8F4 node-pair. For a full XIV, consider 4 to 8 nodes 8F4 models, or 2 to 4 nodes of an 8G4. For read-intensive cache-friendly workloads, an SVC in front of XIV was able to deliver over 300,000 IOPS.

• A single node TS7650G ProtecTIER can handle 6 to 9 XIV modules. Two nodes of TS7650G were needed to drivea full 15-module XIV. A single node TS7650 in front of XIV was able to ingest 680 MB/sec on the seventh day with17 percent per-day change rate test workload using 64 virtual drives. Reading the data back got over 950 MB/sec.

• For SAP environments where response time 20-30 msec are acceptable, the 15-module XIV delivered over 60,000 IOPS. Reducing this down to 25,000-30,000 cut the msec response time to a faster 10-15 msec.

These were all done as internal lab tests. Your mileage may vary.

Not surprisingly, XIV was quite the popular topic here this week at the Storage Symposium. There were many moresessions, but these were the only two that I attended.

technorati tags: IBM, XIV, SATA, best practices, performance, Wilson Kipketer, massive parallelism, HBA, DBMS, Oracle, ASM, DB2, SVC, VMware, VMFS, TSM, Tivoli, SAP, Quicksizer, SAPS, PERFMON, iostat, Disk+Magic, TS7650G, ProtecTIER

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Tags:  disk tape

Continuing my week in Chicago, for the IBM Storage Symposium 2008, we had sessions that focused on individual products. IBM System Storage SAN Volume Controller (SVC) was a popular topic.

SVC - Everything you wanted to know, but were afraid to ask!

Bill Wiegand, IBM ATS, who has been working with SAN Volume Controller since it was first introduced in 2003. answered some frequently asked questions about IBM System Storage SAN Volume Controller.

1. Do you have to upgrade all of your HBAs, switches and disk arrays to the recommended firmware levels before upgrading SVC? No. These are recommended levels, but not required. If you do plan to update firmware levels, focus on the host end first, switches next, and disk arrays last.
   
2. How do we request special support for stuff not yet listed on the Interop Matrix? Submit an RPQ/SCORE, same as for any other IBM hardware.
   
3. How do we sign up for SVC hints and tips? Go to the IBM [SVC Support Site] and select the "My Notifications" under the "Stay Informed" box on the right panel.
   
4. When we call IBM for SVC support, do we select "Hardware" or "Software"? While the SVC is a piece of hardware, there are very few mechanical parts involved. Unless there are sparks, smoke, or front bezel buttons dangling from springs, select "Software". Most of the questions are related to the software components of SVC.
   
5. When we have SVC virtualizing non-IBM disk arrays, who should we call first? IBM has world-renown service, with some of IT's smartest people working the queues. All of the major storage vendors play nice as part of the [TSAnet Agreement when a mutual customer is impacted. When in doubt, call IBM first, and if necessary, IBM will contact other vendors on your behalf to resolve.
   
6. What is the difference between livedump and a Full System Dump? Most problems can be resolved with a livedump. While not complete information, it is generally enough, and is completely non-disruptive. Other times, the full state of the machine is required, so a Full System Dump is requested. This involves rebooting one of the two nodes, so virtual disks may temporarily run slower on that I/O group.
   
7. What does "svc_snap -c" do? The "svc_snap" command on the CLI generates a snap file, which includes the cluster error log and trace files from all nodes. The "-c" parameter includes the configuration and virtual-to-physical mapping that can be useful for disaster recovery and problem determination.
   
8. I just sent IBM a check to upgrade my TB-based license on my SVC, how long should I wait for IBM to send me a software license key? IBM trusts its clients. No software license key will be sent. Once the check clears, you are good to go.
   
9. During migration from old disk arrays to new disk arrays, I will temporarily have 79TB more disk under SVC management, do I need to get a temporary TB-based license upgrade during the brief migration period? Nope. Again, we trust you. However, if you are concerned about this at all, contact IBM and they will print out a nice "Conformance Letter" in case you need to show your boss.
   
10. How should I maintain my Windows-based SVC Master Console or SSPC server? Treat this like any other Windows-based server in your shop, install Microsoft-recommended Windows updates, run Anti-virus scans, and so on.
    
11. Where can I find useful "How To" information on SVC? Specify "SAN Volume Controller" in the search field of the [IBM Redbooks vast library of helpful books.
    
12. I just added more managed disks to my managed disk group (MDG), can I get help writing a script to redistribute the extents to improve wide-striping performance? Yes, IBM has scripting tools available for download on [AlphaWorks]. For example, svctools will take the output of the "lsinfo" command, and generate the appropriate SVC CLI to re-migrate the disks around to optimize performance. Of course, if you prefer, you can use IBM Tivoli Storage Productivity Center instead for a more automated solution.
    
13. Any rules of thumb for sizing SVC deployments? IBM's Disk Magic tool includes support for SVC deployments. Plan for 250 IOPS/TB for light workloads, 500 IOPS/TB for average workloads, and 750 IOPS/TB for heavy workloads.
    
14. Can I migrate virtual disks from one manage disk group (MDG) to another of different extent size? Yes, the new Vdisk Mirroring capability can be used to do this. Create the mirror for your Vdisk between the two MDGs, wait for the copy to complete, and then split the mirror.
    
15. Can I add or replace SVC nodes non-disruptively? Absolutely, see the Technotes [SVC Node Replacement page.


16. Can I really order an SVC EE in Flamingo Pink? Yes. While my blog post that started all this [Pink It and Shrink It] was initially just some Photoshop humor, the IBM product manager for SVC accepted this color choice as an RPQ option. The default color remains Raven Black.

technorati tags: IBM, SVC, Audacity of Cope, svc_snap, Flamingo pink, Raven black, non-disruptive, svctools, AlphaWorks

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Tags:  disk

Back in June, I mentioned this blog was [Moving to MyDeveloperWorks] which is based on IBM Lotus Connections. Finally, the move is complete for all bloggers. If you are having problems with the redirects, you might need to unsubscribe and re-subscribe in your RSS feed reader. Here are the new links for several IBM bloggers that have moved over:

• [Inside System Storage - Tony Pearson]
• [Storage Virtualization - Barry Whyte]
• [Green Speed - Carlos Pratt]
• [Benchmarking and Systems Performance - Elisabeth Stahl"]

Let me know what you think of the "XIV" color scheme of Black and Orange. I have not yet "tricked out" the template with all the latest bells and whistles, widgets and so on, that is still work to do.

technorati tags: IBM, MyDeveloperWorks, Barry Whyte, Carlos Pratt, Elisabeth Stahl, XIV

Tags:  blogging

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