Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people, just like you, are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
Solved

Help Calculating IOPS.

Posted on 2011-02-21
6
1,281 Views
Last Modified: 2013-11-14
I need a little help when trying to calulate available IOPS in a raid array.  I have been looking at wmarrow's calculator (http://www.wmarow.com/strcalc/) and I am a little lost when it gets to read cache hit ratio and write cache hit ratio.  With four 7200rpm sata 3.0 drives in a raid 10 I get between 227 and 23000 IOPS (at 70%/30% read/write ratio) depending on how I manipulate these two fields.  How should I properly calculate these two fields?

I realize that in production I would want fast 15K SAS drives, and as many as possible, but this is for a lab environment and I do not have the budget for SAS drives.  Just need to get an estimate of how many iops I will have to deal with so I don't overtax the box.  It will be running vSphere Hypervisor 4.1.
0
Comment
Question by:arstacey
6 Comments
 
LVL 119
ID: 34945157
0
 
LVL 6

Assisted Solution

by:Gugro
Gugro earned 250 total points
ID: 34945163
leave the read and write cache ratio at 0.
Disks have normally only a small cache ( typical 8-32 MB ), the chance that you will hit data in this cache ( and the data was NOT found in the OS or DB cache ) is almost zero.
0
 
LVL 3

Accepted Solution

by:
driskollt earned 250 total points
ID: 35132834
Don't factor in caching for random loads.  Eventually everything has to hit the disk so you'll take the hit somewhere.  Also, when in doubt, assume random.  Most workloads are random.  Sequentual workloads are usually things like backups, logs, data warehousing.

To calculate total sustained IOPS that a set of disks can handle for SATA w/ RAID10 and 33% writes...
A single 7200 SATA can handle about 80 sustained random IOPS.
IOPS=(80IOPS * 4disks)/(.67 + (2 * .33))
240 IOPS.
 

0
Three Reasons Why Backup is Strategic

Backup is strategic to your business because your data is strategic to your business. Without backup, your business will fail. This white paper explains why it is vital for you to design and immediately execute a backup strategy to protect 100 percent of your data.

 
LVL 3

Expert Comment

by:driskollt
ID: 35132860
Oops, sorry you wanted 70% read.

Anyway...

Total IOPS = (DriveIOPS * #Drives) / (ReadRatio + (RAIDWritePenalty * WriteRatio))
So.
246IOPS = (80 * 4) / (.7 + (2 * .3))

0
 

Author Comment

by:arstacey
ID: 35133522
Ok, so with that in mind, a RAID 10 array of 8 Sata 7200rpm 1tb drives gives me roughly 4TB of storage and 426 IOPS.  If a windows 7 desktop requires roughly 20 IOPS virtualized, then I should be able to run a Server 2008 Server Core running DC, File Shareing, DNS, and DHCP roles as well as at least 16 Win 7 desktops all virtualized under VMWare ESXi?  The server will probably only have 1 quad core xeon processor, an e5620 2.4 Ghz with Hyperthreading, and at least 24GB Ram.
0
 
LVL 3

Expert Comment

by:driskollt
ID: 35138023
You're probably fine.  Especially if it's just a lab.  If your lab doesn't have SLAs for response time/etc, then I wouldn't worry about it too much.  

Since it's a lab, your write/read ratio is probably going to be more like .85/.15 which will give you a little better performance.

The fact you're using RAID10 with SATA for a random workload is a good idea as well.

0

Featured Post

PRTG Network Monitor: Intuitive Network Monitoring

Network Monitoring is essential to ensure that computer systems and network devices are running. Use PRTG to monitor LANs, servers, websites, applications and devices, bandwidth, virtual environments, remote systems, IoT, and many more. PRTG is easy to set up & use.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
Hit router interface limit 7 37
Changing partitions on external drive, Windows 10 12 54
VMware Fail Over 5 52
VMWare fails to boot after update 15 35
If we need to check who deleted a Virtual Machine from our vCenter. Looking this task in logs can be painful and spend lot of time, so the best way to check this is in the vCenter DB. Just connect to vCenter DB(default DB should be VCDB and using…
When we purchase storage, we typically are advertised storage of 500GB, 1TB, 2TB and so on. However, when you actually install it into your computer, your 500GB HDD will actually show up as 465GB. Why? It has to do with the way people and computers…
Teach the user how to use create log bundles for vCenter Server or ESXi hosts Open vSphere Web Client: Generate vCenter Server and ESXi host log bundle:  Open vCenter Server Appliance Web Management interface and generate log bundle: Open vCenter Se…
This video shows you how easy it is to boot from ISO images for virtual machines with the ISO images stored on a local datastore on the ESXi host.

839 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question