We help IT Professionals succeed at work.

Disparity between read/write speeds when performing SVMotion

sbumpas
sbumpas asked
on
368 Views
Last Modified: 2014-08-09
Last night I performed a SVMotion on a VM from a SSD to a 6 disk RAID10.  The read/write rates are shown in the attached graphic.  Any idea why my read rate would be 1/2 my write rate?  It seems to me that, at the very least, they should be equal?  How can a disk write faster than the data being read?
710.JPG
Comment
Watch Question

CERTIFIED EXPERT

Commented:
your raid controller uses battery write cache module which is essentially a RAM which has much higher transfer rates than any SSD chips. anyway you can see that these graphs show nothing real and that vmware (and also other vendors) are just giving you something you do not need.

Author

Commented:
The write cache was my first thought, but you can see in the start in the xfer the speeds are much higher - presumably while the cache is in use.  Once cache is full, the speeds bottom out (a bit) but the writes are still 2x faster.  

What do you mean the graphs "show nothing real"?
CERTIFIED EXPERT
Commented:
This one is on us!
(Get your first solution completely free - no credit card required)
UNLOCK SOLUTION
Andrew Hancock (VMware vExpert PRO / EE Fellow)VMware and Virtualization Consultant
CERTIFIED EXPERT
Fellow
Expert of the Year 2017

Commented:
What do you mean the graphs "show nothing real"?

if you want a longer discussion, leave the question to run for longer, for the storage Experts!

Author

Commented:
I would love to know more - do I need to repost since I accepted an answer?
Andrew Hancock (VMware vExpert PRO / EE Fellow)VMware and Virtualization Consultant
CERTIFIED EXPERT
Fellow
Expert of the Year 2017

Commented:
You can request the Question, be "Unaccepted" if you are not happy with the solution provided.

Select Request for Assistance, under the Question Text.

Gain unlimited access to on-demand training courses with an Experts Exchange subscription.

Get Access
Why Experts Exchange?

Experts Exchange always has the answer, or at the least points me in the correct direction! It is like having another employee that is extremely experienced.

Jim Murphy
Programmer at Smart IT Solutions

When asked, what has been your best career decision?

Deciding to stick with EE.

Mohamed Asif
Technical Department Head

Being involved with EE helped me to grow personally and professionally.

Carl Webster
CTP, Sr Infrastructure Consultant
Empower Your Career
Did You Know?

We've partnered with two important charities to provide clean water and computer science education to those who need it most. READ MORE

Ask ANY Question

Connect with Certified Experts to gain insight and support on specific technology challenges including:

  • Troubleshooting
  • Research
  • Professional Opinions
Unlock the solution to this question.
Join our community and discover your potential

Experts Exchange is the only place where you can interact directly with leading experts in the technology field. Become a member today and access the collective knowledge of thousands of technology experts.

*This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

OR

Please enter a first name

Please enter a last name

8+ characters (letters, numbers, and a symbol)

By clicking, you agree to the Terms of Use and Privacy Policy.