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тАО05-28-2002 02:01 AM
тАО05-28-2002 02:01 AM
using Glance, I can see a costantly high value of Qlen for a specific VA7400 LUN (other LUNs of same array are OK).
Where can I indagate furtherly?
Thanks in advance
Mimmus
Solved! Go to Solution.
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тАО05-28-2002 02:22 AM
тАО05-28-2002 02:22 AM
Re: High Qlen on a VA7400
is the concerned LUN on the same node like the other LUNS you talk about?
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тАО05-28-2002 05:51 AM
тАО05-28-2002 05:51 AM
Re: High Qlen on a VA7400
the LUN of this array are all
mounted on the same system.
Now I tried to set queue_depth to an higher value (using sysctl) and to use primary/alternate path according to some performance tips from HP (primary path on controller 1 for LUN in Redundancy Group 1 and viceversa).
I hope in better performance.
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тАО05-28-2002 03:31 PM
тАО05-28-2002 03:31 PM
SolutionIf your queue depth goes to 100 and stays there, you have a performance bottleneck on that LUN. If it does not increase the Glance Qlen, then the array is doing well.
I would say that if it's over 10 to 15, you should split that LUN into two, one on each Redundancy Group (RG), and then stripe them. This should give better performance.
Good luck!
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тАО05-29-2002 04:52 AM
тАО05-29-2002 04:52 AM
Re: High Qlen on a VA7400
Have you allocated more than 1/2 of the space of the array to LUNs ? and if so, is the array in AutoRAID ?
How many spindles are in the array ?
Are you in RAID 5 mode ? and if so, is your application write intensive ?
The cache segment size on the VA7400 is 64 Kbytes. What is the typical read/write transfer size of the application ?
Did you use vxtunefs on the filesystem to set the value of max_buf_data_size so that it would be a better match for the cache segment size ?
Have you checked the fibre channels for errors using fcmsutil ? Sometimes silent errors can create silent retries and slow things down.
How much memory is in the system ? How much of it is being used for buffer cache ?
(If one satisfies more ops out of buffer cache then the array's queue depth will be small)
Enjoy,
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тАО05-29-2002 11:34 PM
тАО05-29-2002 11:34 PM
Re: High Qlen on a VA7400
Thanks for all suggestions