Solved

Dell server slow disks

Posted on 2013-06-26
12
1,020 Views
Last Modified: 2016-11-23
I have setup a new dell server, windows runs from mirrored raid and data volume is raid 5. The raid controller has a battery pack and the disks are set to write through. I am using it for WDS and it seems slow creating windows pe images which I believe relates to disk speed.
I understood the raid battery pack negatates the need for write cache on the disks but I may be mistaken Hopefully someone can fill in the gaps for me.
0
Comment
Question by:Sid_F
[X]
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
  • 4
  • 3
  • 2
  • +1
12 Comments
 
LVL 10

Expert Comment

by:Subhashish Laha
ID: 39277628
As you have the battery backup of cache on RAID controller, you should use Write back caching.

Write trough Caching.
When the controller receives a write request from the host, it stores the data in its cache module, writes the data to the disk drives, then notifies the host when the write operation is complete. This process is calles write-trough caching because the data actually passes through-and is stored in- the cache memory on its way to the disk drives.

Write back caching
This caching technique improves the subsystem's response time to write requests by allowing the controller to declare the write operation 'complete' as soon as the data reaches its cache memory. The controller performs the slower operation of writing the data to the disk drives at a later time.

http://en.community.dell.com/support-forums/servers/f/906/t/11183254.aspx
0
 
LVL 121
ID: 39277641
if you have the option, set to 75% Write and 25% Read.
0
 
LVL 33

Expert Comment

by:PowerEdgeTech
ID: 39278378
Which Dell server?  Which RAID controller?  SAS or SATA disks?  Speed?

If you have an S-series controller, they are (S)oftware RAID and not designed for performance.  If you have an H310, then RAID 5 performance is a "known issue" at Dell for that controller and you would be advised to use a different RAID level.

Also, not all controllers have onboard cache ... only the PERC 5/6, H700, and H710.
0
2017 Webroot Threat Report

MSPs: Get the facts you need to protect your clients.
The 2017 Webroot Threat Report provides a uniquely insightful global view into the analysis and discoveries made by the Webroot® Threat Intelligence Platform to provide insights on key trends and risks as seen by our users.

 
LVL 6

Author Comment

by:Sid_F
ID: 39279002
The issue was the disk cache policy was disabled. As soon as this was enabled for both virtual disks performance was much better. Its done through the dell open manage console
0
 
LVL 6

Author Comment

by:Sid_F
ID: 39280105
I've requested that this question be closed as follows:

Accepted answer: 0 points for Sid_F's comment #a39279002

for the following reason:

Resolved
0
 
LVL 33

Expert Comment

by:PowerEdgeTech
ID: 39280104
I think you marked the wrong post as the answer.  It should be the following, which suggested enabling the cache for optimal performance (although the 13 year old link provided was useless):

http://www.experts-exchange.com/Hardware/Servers/Q_28168112.html#a39277628
0
 
LVL 33

Expert Comment

by:PowerEdgeTech
ID: 39280106
See previous comment.
0
 
LVL 33

Expert Comment

by:PowerEdgeTech
ID: 39283068
Post http:a39277628 should be the answer ... not that it was a perfect answer, but the OP clearly said he did exactly what that post suggested.
0
 
LVL 6

Accepted Solution

by:
Sid_F earned 500 total points
ID: 39283120
Hi,

The settings I selected under write policy were "write through cache" (they were previosuly at write back) for both disks but this made no difference I noticed the field marked "disk cache policy" was set to disabled so I selected change policy and execute and selected enable disk cache policy and the disk was much faster.
0
 
LVL 121
ID: 39283624
just playing devil's avocate here, in post http:#a39277628 it does not state enable disk cache policy!
0

Featured Post

Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

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

In this article, I am going to show you how to simulate a multi-site Lab environment on a single Hyper-V host. I use this method successfully in my own lab to simulate three fully routed global AD Sites on a Windows 10 Hyper-V host.
This article aims to explain the working of CircularLogArchiver. This tool was designed to solve the buildup of log file in cases where systems do not support circular logging or where circular logging is not enabled
This Micro Tutorial will teach you how to reformat your flash drive. Sometimes your flash drive may have issues carrying files so this will completely restore it to manufacturing settings. Make sure to backup all files before reformatting. This w…
In this video tutorial I show you the main steps to install and configure  a VMware ESXi6.0 server. The video has my comments as text on the screen and you can pause anytime when needed. Hope this will be helpful. Verify that your hardware and BIO…
Suggested Courses

636 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