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The various vendors often myopically focus on their individual product and provide little assistance in configuring the other elements of the IO stack to exploit their product, or hints on how to configure their product to exploit other elements of the IO stack. There is not a lot of published "best practice" information regarding DM-Multipath, because "your mileage may vary" depending on characteristics of the storage, host system, SAN topology, Linux IO stack, file system manager and the application itself. and they do NOT agree (and most are "safe", but grossly sub-optimal).įor large configurations, throughput-biased configurations, configurations with more than 2 active paths per LUN, DM-multipath is somewhat "do-it-yourself". Many storage vendors offer nf entries for their storage, but the challenge is that there are often several nf entries listed in different manuals.
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Linux DM-Multipath sets up fairly easily, but the "defaults" can yield under-utilization in high-throughput environments. Few users are back-porting request-based DM-Multipath onto RHEL 5.x,
Emc powerpath license upgrade#
For example, for the RHEL 5.x user to get request-based multipath functionality, most need to upgrade to RHEL 6.x which can introduce compatibility issues beyond DM-Multipath. This tends to link DM-Multipath into the version of the Linux distribution, and the overall compatibility risk when jumping revisions can be greater. With DM-Multipath, most customers use the "in box" version for better supportability.
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Emc powerpath license install#
In many cases, you can install the most recent version of EMC PowerPath on an older version of Linux, potentially improving its IO stack. EMC PowerPath is an additional package that needs to be installed, and as such is independently versioned. But as the hardware and Linux platform advance (such as the new dual-socket Intel Xeon E5-26xx, Sandy Bridge-EP, Romley-EP servers), EMC PowerPath seems to be trailing on being able to fully exploit the server capabilities. Some lack-of-restrictions cannot be fully exploited (yet) due to restrictions elsewhere in the IO stack.
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On the DM-Multipath side, some of the "capabilities" are more of a lack-of-restrictions that may exist in PowerPath. In addition, there is a non-trivial cost difference. With the current RHEL 6.x Request-based DM-Multipath, there are some capabilities in DM-Multipath that exceed EMC PowerPath, and there are EMC PowerPath capabilities that still exceed DM-Multipath. Linux IO stack) evolved more rapidly than EMC PowerPath. In the following years, DM-Multipath (and other native facilities of the The comparison between DM-Multipath and EMC PowerPath would have been very different. Three plus years ago, DM-Multipath was much less mature than EMC PowerPath and other proprietary multipath managers. Several years ago, we specifically asked EMC to support some specific third party storage, and EMC declined, forcing us to use a non-PowerPath solution. We are a large EMC shop that is becoming more multi-vendor in the storage area. This could include multipath-capable boot disks controlled by a host-based RAID adapter. Therefore, to use PowerPath all of your multipath-capable devices need to be supported under PowerPath. EMC PowerPath supports a limited number of non-EMC storage systems, and does NOT interoperate easily with a non-PowerPath multipath manager.