Comments on: Queuedepth, and what’s next? http://www.yellow-bricks.com/2008/07/21/queuedepth-and-whats-next/ Building blocks for virtualization... Fri, 19 Mar 2010 14:22:45 +0000 http://wordpress.org/?v=2.9.2 hourly 1 By: Jorink.nl » Disk.UseLunReset and/or Disk.UseDeviceReset http://www.yellow-bricks.com/2008/07/21/queuedepth-and-whats-next/comment-page-1/#comment-6849 Jorink.nl » Disk.UseLunReset and/or Disk.UseDeviceReset Mon, 01 Mar 2010 15:29:01 +0000 http://www.yellow-bricks.com/?p=219#comment-6849 [...] Source : http://www.yellow-bricks.com/2008/07/21/queuedepth-and-whats-next/ [...] [...] Source : http://www.yellow-bricks.com/2008/07/21/queuedepth-and-whats-next/ [...]

]]> By: So you bought an EqualLogic SAN, now what… part one « Michael Ellerbeck http://www.yellow-bricks.com/2008/07/21/queuedepth-and-whats-next/comment-page-1/#comment-5268 So you bought an EqualLogic SAN, now what… part one « Michael Ellerbeck Mon, 23 Nov 2009 16:07:33 +0000 http://www.yellow-bricks.com/?p=219#comment-5268 [...] So, did you read it? I mean go READ IT. Trust me! What I gleaned from those guides is this: (copied from http://www.yellow-bricks.com/2008/07/21/queuedepth-and-whats-next/ [...] [...] So, did you read it? I mean go READ IT. Trust me! What I gleaned from those guides is this: (copied from http://www.yellow-bricks.com/2008/07/21/queuedepth-and-whats-next/ [...]

]]> By: Welcome to vSphere-land! » Storage Links http://www.yellow-bricks.com/2008/07/21/queuedepth-and-whats-next/comment-page-1/#comment-3397 Welcome to vSphere-land! » Storage Links Fri, 08 May 2009 03:33:56 +0000 http://www.yellow-bricks.com/?p=219#comment-3397 [...] in ESX Server Round Robin Load Balancing Obtaining LUN pathing information for ESX Server 3 Queue Depth How to check if a LUN is locked by a host Scripting Queue Depth in a QLogic/EMC environment [...] [...] in ESX Server Round Robin Load Balancing Obtaining LUN pathing information for ESX Server 3 Queue Depth How to check if a LUN is locked by a host Scripting Queue Depth in a QLogic/EMC environment [...]

]]> By: Duncan Epping http://www.yellow-bricks.com/2008/07/21/queuedepth-and-whats-next/comment-page-1/#comment-738 Duncan Epping Fri, 25 Jul 2008 20:17:12 +0000 http://www.yellow-bricks.com/?p=219#comment-738 Thanks for the excellent reply nick!! this is valuable info, Thanks for the excellent reply nick!! this is valuable info,

]]> By: Nick Triantos http://www.yellow-bricks.com/2008/07/21/queuedepth-and-whats-next/comment-page-1/#comment-737 Nick Triantos Fri, 25 Jul 2008 20:11:55 +0000 http://www.yellow-bricks.com/?p=219#comment-737 There's much more that goes into setting the Queue Depth than making the assumption that a queue depth of X value on the host will be sufficient and will drive high I/O. The fan-in ratio of host ports to a single Target port needs to be considered AND The Queue depth on the Array target port side AND given that A/A multipathing is not officially supported, the Active path for each LUN should be balanced across all front end target ports. If I have a hypotherical Target queue depth per port of 512 and thru that port I expose 4 LUNs (Datastores) to a 4 node ESX cluster with a host queue depth value of 64 on each. Each Host has an Active path thru the Target Port. Then I can, potentially, end up with 4 x 4 x 64 = 1024 outstanding IOs at which point the Target port will issue a QFULL condition simply because it will be saturated. The way FC drivers deal with such conditions is that they will throttle I/O significantly so the target queues have time to clear and thenthe initiator will gradually increase I/O again. The end results is significant latency and for some Operating systems (i.e AIX) this condition will result in an I/O error if 3 consecutive QFULL conditions occur for the same request. I've written an article on Dynamic Queue Depth management and what NetApp has done to control, monitor and dynamically allocate and change queue slot allocations without having to touch the host queue depth value beyond the initial setup. http://partners.netapp.com/go/techontap/matl/fc-sans.html cheers There’s much more that goes into setting the Queue Depth than making the assumption that a queue depth of X value on the host will be sufficient and will drive high I/O.

The fan-in ratio of host ports to a single Target port needs to be considered AND
The Queue depth on the Array target port side AND given that A/A multipathing is not officially supported, the Active path for each LUN should be balanced across all front end target ports.

If I have a hypotherical Target queue depth per port of 512 and thru that port I expose 4 LUNs (Datastores) to a 4 node ESX cluster with a host queue depth value of 64 on each. Each Host has an Active path thru the Target Port.

Then I can, potentially, end up with 4 x 4 x 64 = 1024 outstanding IOs at which point the Target port will issue a QFULL condition simply because it will be saturated.

The way FC drivers deal with such conditions is that they will throttle I/O significantly so the target queues have time to clear and thenthe initiator will gradually increase I/O again. The end results is significant latency and for some Operating systems (i.e AIX) this condition will result in an I/O error if 3 consecutive QFULL conditions occur for the same request.

I’ve written an article on Dynamic Queue Depth management and what NetApp has done to control, monitor and dynamically allocate and change queue slot allocations without having to touch the host queue depth value beyond the initial setup.

http://partners.netapp.com/go/techontap/matl/fc-sans.html

cheers

]]> By: Matt http://www.yellow-bricks.com/2008/07/21/queuedepth-and-whats-next/comment-page-1/#comment-734 Matt Wed, 23 Jul 2008 18:52:09 +0000 http://www.yellow-bricks.com/?p=219#comment-734 Thanks Duncan. Much appreciated. Thanks Duncan. Much appreciated.

]]> By: Duncan http://www.yellow-bricks.com/2008/07/21/queuedepth-and-whats-next/comment-page-1/#comment-733 Duncan Wed, 23 Jul 2008 18:40:10 +0000 http://www.yellow-bricks.com/?p=219#comment-733 yes you can, but i would recommend doing it asap. yes you can, but i would recommend doing it asap.

]]> By: Matt http://www.yellow-bricks.com/2008/07/21/queuedepth-and-whats-next/comment-page-1/#comment-732 Matt Wed, 23 Jul 2008 17:56:16 +0000 http://www.yellow-bricks.com/?p=219#comment-732 I can run it and reboot at a later date correct? I can run it and reboot at a later date correct?

]]> By: Duncan http://www.yellow-bricks.com/2008/07/21/queuedepth-and-whats-next/comment-page-1/#comment-731 Duncan Wed, 23 Jul 2008 17:55:01 +0000 http://www.yellow-bricks.com/?p=219#comment-731 it sets up the information required for booting which includes this parameter. it sets up the information required for booting which includes this parameter.

]]> By: Matt http://www.yellow-bricks.com/2008/07/21/queuedepth-and-whats-next/comment-page-1/#comment-729 Matt Wed, 23 Jul 2008 15:36:48 +0000 http://www.yellow-bricks.com/?p=219#comment-729 What does that command do? What does that command do?

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