Condusiv Technologies Blog

Condusiv Technologies Blog

Blogging @Condusiv

The Condusiv blog shares insight into the issues surrounding system and application performance—and how I/O optimization software is breaking new ground in solving those issues.

Microsoft SQL Team Puts V-locity to the Test

by Brian Morin 15. September 2017 09:12

In a testament to Condusiv's longstanding 20+ year relationship with Microsoft® as a Gold Partner and provider of technologies to Microsoft over the years, Condusiv® became the first software vendor awarded the stringent certification of MS-SQL Server I/O Reliability joining a very short list containing the likes of Dell® / EMC®, IBM® and HPE®.

Microsoft developed the SQL Server I/O Reliability Program to ensure the reliability, integrity, and availability of vendor products with SQL Server. The program includes a set of requirements that, when complied with and approved by a Microsoft committee of engineers, ensure the product is fully reliable and highly available for SQL Server systems. The certification applies to SQL Server running on Windows Server 2008R2 and later (the most current 2016 release included).

V-locity® Certified for SQL I/O Reliability and Demonstrates Significant SQL Performance Gains

The program itself does not require performance characteristics of products, but it does require I/O testing to exhibit the reliability and integrity of the product. To that end, the full report links to a summary of before/after performance results from a HammerDB test (the preferred load test to measure MS-SQL performance) on Azure to demonstrate the gains of using V-locity I/O reduction software for SQL Server 2016 on Azure’s Windows Server 2016 Data Center Edition. While transactions per minute increased 28.5% and new orders per minute increased by 28.7%, gains were considered modest by Condusiv’s standards since only a limited amount memory was available to be leveraged by V-locity’s patented DRAM caching engine. The typical V-locity customer sees 50% or better performance improvement to SQL applications. The Azure test system configured by Microsoft did not boost available memory to showcase the full power of what V-locity can do with as little of 2-4GB of memory.

To read the full report CLICK HERE

 

Help! I deleted a file off the network drive!!

by Robin Izsak 31. October 2013 08:01

What if the recycle bin on your clients could be expanded to include file servers? And what if you could enable your users to recover their own files with self-service recovery? You would never have to dig through backups to restore files again, or schedule incessant snapshots to protect data.

One of the most persistent—and annoying—help desk calls is to help users recover files accidentally deleted off network drives, or support users who ‘saved over’ a PowerPoint they need for a meeting—in 15 minutes.

There are some pretty serious holes in true continuous data protection: First, any data that was created between backups might not be recoverable. Second, who wants to dig through backups anyway? Third, you’d have to schedule an insane amount of snapshots to protect every version of every file. Fourth, the Windows recycle bin doesn’t catch files deleted off a network drive, which is how most of us work in the real world—networks, clouds—not local drives.

Check out our latest guide that explains the gap between backup and the Windows recycle bin, and how to bridge that gap with Undelete® to ensure continuous data protection and self-service file recovery.

Meet the recycle bin for file servers. You’re welcome.

Optimizing Virtual Platform Disk Performance (ESX)

by Michael 28. June 2011 07:38

Overview 

The intensified demand for IT network efficiency and lower operating costs has been driving the phenomenal growth of virtualization in the past decade, with no signs of slowing. At present, many corporations run more virtualized servers than physical servers.

 

While virtualization provides opportunity for consolidation and better hardware utilization, it’s critically important to recognize and never exceed hardware capacities.  

The importance of ensuring sufficient CPU and memory are well understood, with many processes and management tools available to help plan and properly provision VMs for these critical resources. I/O traffic, network and disk, are more complicated to account for in virtual environments as they tend to be more unpredictable.

In order to better accommodate disk I/O, most virtualization platforms will implement a Storage Area Network (SAN) which can offer greater data throughput, and a dynamic environment to address fluctuations in I/O demands.

While a storage infrastructure can be built out to meet expected demands, there are uncontrollable behaviors that will still impede performance. 

File Fragmentation

As files are written to a general purpose local disk file systems, such as Windows NTFS, a natural byproduct is file fragmentation. File fragmentation is a state in which the data stream of a file is stored in non-contiguous clusters in the file system. Fragmentation occurs on logical volume, and by device drivers is translated to logical blocks, and eventually to physical sectors residing on a storage device. It can be demonstrated as pieces of a file located in a non-contiguous manner. The effect of this file fragmentation is increased I/O overhead, leading to slower system performance for the operating system.

In the case of virtual platforms, a guest operating systems is stored as a file (i.e. set of files) on the virtual platforms file system as a “virtual disk”. A virtual disk is essentially a container file, housing all the files that constitute the OS and user data of a VM.  A virtual disk files can fragment just as any other file can resulting in what amounts to a “logically” fragmented virtual hard disk, which still has typical file fragmentation contained within it. The picture represented to the right would appear as “VirtualServer1.vmdk, 30GB in size, in 4 pieces”.  

 

This situation equates to hierarchical fragmentation or more simply fragmentation-within-fragmentation. Given the relatively static nature and large size of virtual disks, and large allocation unit size of VMFS (typically 1MB), fragmentation of these files is unlikely to cause performance issues in most cases. The focus and solution to fragmentation should be directed at the guest operating system.

Fragmentation within a Windows VM will cause Windows to generate additional unnecessary I/O. This added I/O traffic can be discovered using Windows Performance Monitor, where it is one of the principal causes for Split I/O.  

 

Fragmentation prevention and defragmentation technologies exist to eliminate unnecessary I/O overhead, and improve system performance. Fragmentation prevention solves fragmentation at the source, by actively causing files to be written contiguously via advanced files system drivers. Defragmentation is the action in which file fragments are re-aligned within the file system, into a single extent, so that only the minimal amount of disk I/Os are required to access the file, thereby increasing access speed.  

Partition Alignment 

Depending on your storage protocol and virtual disk type, misaligned partitions can cause additional unnecessary I/O[1]. In the example below in which the ESX and SAN volumes are not properly aligned, a Word file spanning four NTFS clusters causes additional unnecessary I/O in both VMFS and the SAN LUN.  

 

Similarities between Partition Alignment and Fragmentation 

Much like misaligned partitions can cause additional I/O at multiple layers, so does fragmentation. While partitions can be properly aligned once and never require further corrective action, fragmentation will continue to occur, and needs to be regularly addressed.

In the example below, which assume proper partition alignment, a file in eight fragments in the guest OS, causes additional I/Os to be generated at the virtualization platform layer[2] and at the LUN.   

 

Defragmentation in the guest operating system (of this file), eliminates excess I/O when accessing the file as Windows only generates one I/O. This reduction in I/O traffic translates to the host file system and SAN LUN, ensuring efficiencies at each layer.   

 

Best Practices 

Defragmentation of Windows file systems is a VMware recommended performance solution. The VMware Knowledge Base article 1004004[3] states “Defragmenting a disk is required to address problems encountered with an operating system as a result of file system fragmentation. Fragmentation problems result in slow operating system performance.” In order to validate the Vmware statement, tests were performed.

 

Test Environment

  
Configuration

Test Environment Configuration Host OS: ESX Server 4.1 with VMFS (1MB blocks)

Guest OS: Windows Server 2008r2 x64 (3GB RAM, 1 vCPU)

Benchmarking Software: Iometer (http://www.iometer.org/)

Fragmentation Program: FragmentFile.exe (used to fragment a specified file)

Defragmentation Software: V-locity® 3.0 (http://www.diskeeper.com/business/v-locity/)

 

Storage: 10GB test volume in a 40GB virtual disk. VMFS Datastore of 410GB. HP Smart Array P400 controller. RAID 5 (4x 136GB SCSI at 10K RPM) Stripe size of 64KB with a 64KB offset (properly aligned).

Load Generation 

The industry standard benchmarking tool Iometer was used to generate I/O load for these experiments.  

Iometer configuration options used as variables in these experiments:

• Transfer request sizes: 1KB, 4KB, 8KB, 16KB, 32KB, 64KB, 72KB, and 128KB

• Percent random or sequential distribution: for each transfer request size, 0 percent and 100 percent random accesses were selected

• Percent read or write distribution: for each transfer request size, 0 percent and 100 percent read accesses were selected 

Iometer parameters that were held constant for all tests:

• Size of volume: 10GB

• Size of Iometer test file (iobw.tst): 8,131,204 KB (~7.75GB)

• Number of outstanding I/O operations: 16

• Runtime: 4 minutes

• Ramp-up time: 60 seconds

• Number of workers to spawn automatically: 1 

The following is excerpted from a VMware white paper[4], and helps to explain why the Iometer parameters were used. 

Servers typically run a mix of workloads consisting of different access patterns and I/O data sizes.

Within a workload there may be several data transfer sizes and more than one access pattern.There are a few applications in which access is either purely sequential or purely random. For example, database logs are written sequentially. Reading this data back during database recovery is done by means of a sequential read operation. Typically, online transaction processing (OLTP) database access is predominantly random in nature. 

The size of the data transfer depends on the application and is often a range rather than a single value. For Microsoft Exchange, the I/O size is generally small (from 4KB to 16KB), Microsoft SQL Server database random read and write accesses are 8KB, Oracle accesses are typically 8KB, and Lotus Domino uses 4KB. On the Windows platform, the I/O transfer size of an application can be determined using Perfmon.

In summary, I/O characteristics of a workload are defined in terms of the ratio of read operations to write operations, the ratio of sequential accesses to random accesses, and the data transfer size. Often, a range of data transfer sizes may be specified instead of a single value.  

Create Fragmentation 

The FragmentFile.exe tool was used to fragment the Iometer test file (iobw.tst) into 568,572 fragments, a mid-range amount of fragmentation for a production server. The statistics collected from an analysis of the volume (shown below) were performed with V-locity.

Test Procedure 

The primary objective was to characterize the performance of fragmented versus defragmented virtual machines for a range of data sizes across a variety of access patterns. The data sizes selected were 1KB, 4KB, 8KB, 16KB, 32KB, 64KB, 72KB, and 128KB. The access patterns were restricted to a combination of 100 percent read or write and 100 percent random or sequential. Each of these four workloads was tested for eight data sizes, for a total of 32 data points per workload.

In order to isolate the impact of fragmentation only the test VM was powered on and active for the duration of the tests.

For the initial run, Iometer created a non-fragmented file, and performance data was collected. Then FragmentFile.exe tool was used to fragment the Iometer test file, the VM rebooted, and the test procedure re-run. This resulted in data sets for both non-fragmented and fragmented scenarios. The results are graphed below.  

Performance Results  

As the graphs show, all workloads show an increase in throughput when the volume [file] is defragmented (i.e. not fragmented).  It also becomes clear that as the I/O read/write size increases, the fragmentation-induced I/O latency increases dramatically.  The greatest improvements of a contiguous file are found with file reads; both random and sequential. 

 

Random Reads  
 
Random Writes 

Sequential Reads

Sequential Writes

Conclusion

 

Fragmentation demonstratively impedes performance of Windows guest operating systems.  While the tests depicted were executed on a singular VM, the issue becomes exponentially worse in a multi-VM environment wherein each VM suffers from file fragmentation.  As server virtualization establishes a symbiotic relationship, it is important to remember that generating disk I/O in one virtual machine affects I/O requests from other virtual systems.  Therefore latencies in one VM will artificially inflate latency in co-located virtual machines (VMs that share a common platform).  

Fragmentation artificially inflates the amount of disk I/O requests which, on a virtual machine platform, compounds the disk bottleneck even more so than on conventional systems.

Eliminating fragmentation in VMs, and the corresponding unnecessary disk I/O traffic, is vital to platform-wide performance and enhances the ability to host more VMs on a shared infrastructure.

You can download the PDF white paper here: Optimizing Virtual Platform Disk Performance.pdf (1.04 mb)

[1] VMware guide to proper partition alignment: http://www.vmware.com/pdf/esx3_partition_align.pdf
[2] It should be noted that VMFS, in the example above need only read the actual amount of data requested in multiples of 512 byte sectors, and does not need to read an entire 1MB block.  
              

Tags:

SAN | Defrag | V-Locity | SAN | VMware | V-Locity | white paper | VMware | white paper

Windows IT Pro Study - Defragmentation Benefits

by Michael 19. November 2010 03:14

Windows IT Pro recently undertook a survey of users who have applied Diskeeper across their network. The purpose was to uncover the benefits achieved from this solution.

It covers points such as...

Increased hardware life, and reduction in unnecessary I/O:

Improved system stability and less crashes:

Less drive failures and data loss:

Faster backups and bootups:

 

Their conclusion?

“Low overhead in system resources, significant documented potential improvements in performance and reliability, along with the improved user productivity and better IT resource utilization demonstrate beyond a doubt that Diskeeper software isn’t just a “nice to have” option in your standard system configuration for the effective business IT department. It is a “must have” in order to obtain the best possible performance and ROI on your servers and workstations.”

Read the full paper here: Windows IT Pro Reliability white paper.pdf (2.10 mb)

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