Original Message:
Sent: Mon May 29, 2023 03:00 AM
From: Nezih Boyacioglu
Subject: Storage Virtualize number of paths
As a writer of this chapter in the IBM Redbook, I totally agree with Andrew. In a Hyperswap environment, you have two FlashSystems, and your logical volume has two physical copies. if your host zoned with those two FlashSystems your host's single port is zoned with each of the 4 controllers, and two ports become 8 paths.
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Nezih Boyacioglu
Original Message:
Sent: Mon May 29, 2023 02:19 AM
From: T Masteen
Subject: Storage Virtualize number of paths
Hello Andrew,
Thanks for reply.
I'm not sure what you mean with two systems?
In a stretched cluster the IOgroups are like in a normal SVC cluster in 1 system (Cluster) and the nodes of these IOgroups are just stretched over two Sites.
A VDisk is "belonging" to 1 IOgroup (just like a normal SVC cluster) and the host is zoned to that IOgroup.
So I still dont see the difference in recommendation between 4 and 8 paths.
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T Masteen
Original Message:
Sent: Mon May 29, 2023 01:16 AM
From: ANDREW GREENFIELD
Subject: Storage Virtualize number of paths
With either HS or SC, you have two systems, ergo each system should have 4 paths, so 4+4, yields the 8 paths for HS/SC configurations, ensuring each cluster set of nodes have 4 paths, each, without too much further Host path management.
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ANDREW GREENFIELD
Original Message:
Sent: Sun May 28, 2023 06:03 AM
From: T Masteen
Subject: Storage Virtualize number of paths
Hello All,
In IBM Redbook Performance and Best Practices Guide for IBM Spectrum Virtualize 8.5 is stated:
Chapter 2.4.5 Host Zones
Note: Eight paths per volume are supported. However, this design provides no
performance benefits and in some circumstances can reduce performance. Also, it does
not significantly improve reliability nor availability. However, fewer than four paths do not
satisfy the minimum redundancy, resiliency, and performance requirements.
Chapter 8.1.1 Number of paths
As a best practice, limit the total number of FC paths per volume to four. For HyperSwap and
stretched cluster configurations, eight paths per volume are recommended. Adding paths
does not significantly increase redundancy, and it tends to bog down the host with path
management. Also, too many paths might increase the failover time.
No I would like to understand why eight paths for a Hyperswap and Stretched Cluster configuration?
Thanks!
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TMasteen
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