Solved

Do I have an Ultra160 Disk Bottleneck?

Posted on 2004-04-30
9
253 Views
Last Modified: 2010-04-03
Hi all,

I've been trying to determine if I indeed have an Ultra160 disk bottleneck on our system.  The system is a Netfinity 7100 running Win2k.  I've got 3 RAID 5 arrays and 1 mirrored array.  When running performance monitor during disk access slow downs, I notice that the disk queue length passes from 0 to more than 50 as soon as the total "disk byte/sec " counter reaches 40 MB/sec.  It doesn't matter if the 40 MB/sec is reached on indivudual arrays or for all the arrays combined. Unless I am dead wrong, this is well below the theoretical 160 MB/sec that Ultra 160 is supposed to deliver.

Does that indicate I have a disk subsystem bottleneck?  Is there something else I am missing or should check?  

Thanks in advance.
0
Comment
Question by:TechnoBuzz
[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
9 Comments
 
LVL 69

Accepted Solution

by:
Callandor earned 125 total points
ID: 10964220
That 160 number is rarely reached, and only if the disk cache is being used, which empties out in a matter of seconds.  80MB/sec is a more realistic number for maximum throughput on the outside cylinders with everything else optimized.  A tool like HDTach will tell you what your array will deliver.
0
 
LVL 2

Expert Comment

by:Phill_upson
ID: 10964772
Also depends on the quality of your RAID controllers and other disks on each chain.  One cable supporting 2 hard disks might be capable of 160MB/sec theoretically, but if you have a UDMA 66 disk on the same chain, access will be held up by that disk.  Again, always worth checking the quality of your cable, bad or cheap cables can cause problems of their own.

From the HDTach reading (tool mentioned above) if you have a spare machine, try putting the disk in there on its own port and HDTach it again, that way you can try and identify if the disk is the issue and contact the manufacturer.
0
 

Expert Comment

by:redking44
ID: 11010008
I have not played RAID so i can only comment on SCSI in general

it's interesting that you top out at 40 MB/sec - which is the SCSI-UW spec. ALmost any other speed and i'd say it ws a bottleneck of some sort,  but this is a stanbdard SCSI speed so i'm sure it's related.

I'd make sure the cables were really U-160 cables, and not UW cables. This may not be easy because they look identical.  I'd also check the setup in the SCSI card(s) - they can be set to work at any speed you choose, and might be throttled back to 40MB/sec..

i suppose...  are your disks really u160  drives?
0
Technology Partners: 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!

 
LVL 69

Expert Comment

by:Callandor
ID: 11372630
TechnoBuzz,

Have your questions been answered?  We haven't heard from you, so why the C grade?
0
 

Author Comment

by:TechnoBuzz
ID: 11397266
Thanks for the link.

Considering this, please change the grade to a "B", since it is after all more approriate.

Thanks Callandor for your input.
0
 
LVL 69

Expert Comment

by:Callandor
ID: 11398560
Thanks for looking over the grading guidelines.
0

Featured Post

Best Practices: Disaster Recovery Testing

Besides backup, any IT division should have a disaster recovery plan. You will find a few tips below relating to the development of such a plan and to what issues one should pay special attention in the course of backup planning.

Question has a verified solution.

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

The business world is becoming increasingly integrated with tech. It’s not just for a select few anymore — but what about if you have a small business? It may be easier than you think to integrate technology into your small business, and it’s likely…
Many businesses neglect disaster recovery and treat it as an after-thought. I can tell you first hand that data will be lost, hard drives die, servers will be hacked, and careless (or malicious) employees can ruin your data.
This video teaches viewers how to encrypt an external drive that requires a password to read and edit the drive. All tasks are done in Disk Utility. Plug in the external drive you wish to encrypt: Make sure all previous data on the drive has been …
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…

707 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