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Path Management and SAN Boot with MPIO on AIX

Path Management and SAN Boot with MPIO on AIX. John Hock jrhock@us.ibm.com Dan Braden dbraden@us.ibm.com Power Systems Advanced Technical Skills. Agenda. Correctly Configuring Your Disks Filesets for disks and multipath code Multi-path basics Multi Path I/O (MPIO) Useful MPIO Commands

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Path Management and SAN Boot with MPIO on AIX

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  1. Path Management and SAN Boot with MPIO on AIX John Hock jrhock@us.ibm.com Dan Braden dbraden@us.ibm.com Power Systems Advanced Technical Skills

  2. Agenda • Correctly Configuring Your Disks • Filesets for disks and multipath code • Multi-path basics • Multi Path I/O (MPIO) • Useful MPIO Commands • Path priorities • Failed Path Recovery and path health checking • MPIO path management • SDD and SDDPCM • Multi-path code choices for DS4000, DS5000 and DS3950 • XIV & Nseries • SAN Boot © 2011 IBM Corporation

  3. https://tuf.hds.com/gsc/bin/view/Main/AIXODMUpdates ftp://ftp.emc.com/pub/elab/aix/ODM_DEFINITIONS/ Disk configuration • The disk vendor… • Dictates what multi-path code can be used • Supplies the filesets for the disks and multipath code • Supports the components that they supply • A fileset is loaded to update the ODM to support the storage • AIX then recognizes and appropriately configures the disk • Without this, disks are configured using a generic ODM definition • Performance and error handling may suffer as a result • # lsdev –Pc disk displays supported storage • The multi-path code will be a different fileset • Unless using the MPIO that’s included with AIX Beware of generic “Other” disk definition No command queuing. Poor Performance & Error Handling © 2011 IBM Corporation

  4. Server FC Switch Storage How many paths for a LUN? • Paths = (# of paths from server to switch) x (# paths from storage to switch) …Here there are potentially 6 paths per LUN …But reduced via: • LUN masking at the storage Assign LUNs to specific FC adapters at the host, and thru specific ports on the storage • Zoning WWPN or SAN switch port zoning • Dual SAN fabrics divides potential paths by two • 4 paths per LUN are sufficient for availability and reduces CPU overhead for choosing the path • Path selection overhead is relatively low—usually negligible • MPIO has no practical limits to number of paths • Other products have path limits • SDDPCM limited to 32 paths per LUN © 2011 IBM Corporation

  5. Server FC Switch Storage 4 X 4 = 16 2 X 2 + 2 X 2 = 8 How many paths for a LUN?, cont’dDual SAN Fabric Reduces Potential Paths © 2011 IBM Corporation

  6. Path selection benefits and costs • Path selection algorithms choose a path to hopefully minimize latency added to an IO to send it over the SAN to the storage • Latency to send a 4 KB IO over a 8 Gbps SAN link is 4 KB / (8 Gb/s x 0.1 B/b x1048576 KB/GB) = 0.0048 ms • Multiple links may be involved, and IOs are round trip • As compared to fastest IO service times around 1 ms • If the links aren’t busy, there likely won’t be much, if any, savings from use of sophisticated path selection algorithims vs. round robin • Costs of path selection algorithms • CPU cycles to choose the best path • Memory to keep track of in-flight IOs down each path, or • Memory to keep track of IO service times down each path • Latency added to the IO to choose the best path Generally utilization of links is low © 2011 IBM Corporation

  7. Multi-path IO with VIO and VSCSI LUNs • Two layers of multi-path code: VIOC and VIOS • VSCSI disks always use AIX default MPIO and all IO for a LUN normally goes to one VIOS • algorithm = fail_over only • VIOS uses the multi-path code specified for the disk subsystem • Set the path priorities for the VSCSI hdisks so half use one VIOS, and half use the other VIO Client MPIO VIO Server Multi-path code VIO Server Multi-path code Disk Subsystem © 2011 IBM Corporation

  8. Multi-path IO with VIO and NPIV • VIOC has virtual FC adapters (vFC) • Potentially one vFC adapter for every real FC adapter in each VIOC • Maximum of 64 vFC adapters per real FC adapter recommended • VIOC uses multi-path code that the disk subsystem supports • IOs for a LUN can go thru both VIOSs • One layer of multi-path code VIO Client Multi-path code VFC VFC VFC VFC VIO Server VIO Server Disk Subsystem © 2011 IBM Corporation

  9. What is MPIO? • MPIO is an architecture designed by AIX development (released in AIX V5.2) • MPIO is also a commonly used acronym for Multi-Path IO • In this presentation MPIO refers explicitly to the architecture, not the acronym • Why was the MPIO architecture developed? • With the advent of SANs, each disk subsystem vendor wrote their own multi-path code • These multi-path code sets were usually incompatible • Mixing disk subsystems was usually not supported on the same system, and if they were, they usually required their own FC adapters • Integration with AIX IO error handling and recovery • Several levels of IO timeouts: basic IO timeout, FC path timeout, etc • MPIO architecture details available to disk subsystem vendors • Compliant code requires a Path Control Module (PCM) for each disk subsystem • Default PCMs for SCSI and FC exist on AIX and often used by the vendors • Capabilities exist for different path selection algorithms • Disk vendors have been moving towards MPIO compliant code MPIO Common Interface © 2011 IBM Corporation

  10. Overview of MPIO Architecture • LUNs show up as an hdisk • Architected for 32 K paths • No more than 16 paths are necessary • PCM: Path Control Module • Default PCMs exist for FC, SCSI • Vendors may write optional PCMs • May provide commands to manage paths • Allows various algorithms to balance use of paths • Full support for multiple paths to rootvg Tip: to keep paths <= 16, group sets of 4 host ports and 4 storage ports and balance LUNs across them • Hdisks can be Available, Defined or non-existent • Paths can also be Available, Defined, Missing or non-existent • Path status can be enabled, disabled or failed if the path is Available (use chpath command to change status) • Add path: e.g. after installing new adapter and cable to the disk run cfgmgr (or cfgmgr –l <adapter>) • One must get the device layer correct, before working with the path status layer © 2011 IBM Corporation

  11. MPIO support © 2011 IBM Corporation

  12. Non-MPIO multi-path code © 2011 IBM Corporation

  13. Mixing multi-path code sets • The disk subsystem vendor specifies what multi-path code is supported for their storage • The disk subsystem vendor supports their storage, the server vendor generally doesn’t • You can mix multi-path code compliant with MPIO and even share adapters • There may be exceptions. Contact vendor for latest updates.HP example: “Connection to a common server with different HBAs requires separate HBA zones for XP, VA, and EVA” • Generally one non-MPIO compliant code set can exist with other MPIO compliant code sets • Except that SDD and RDAC can be mixed on the same LPAR • The non-MPIO compliant code must be using its own adapters • Devices of a given type use only one multi-path code set • e.g., you can’t used SDDPCM for one DS8000 and SDD for another DS8000 on the same AIX instance © 2011 IBM Corporation

  14. Sharing Fibre Channel Adapter ports • Disk using MPIO compliant code sets can share adapter ports • It’s recommended that disk and tape use separate ports Disk (typicaly small block random) and tape (typically large block sequential) IO are different, and stability issues have been seen at high IO rates  © 2011 IBM Corporation

  15. MPIO Command Set • lspath – list paths, path status and path attributes for a disk • chpath – change path status or path attributes • Enable or disable paths • rmpath – delete or change path state • Putting a path into the defined mode means it won’t be used (from available to defined) • One cannot define/delete the last path of a device • mkpath – add another path to a device or makes a defined path available • Generally cfgmgr is used to add new paths • chdev – change a device’s attributes (not specific to MPIO) • cfgmgr – add new paths to an hdisk or make defined paths available (not specific to MPIO) © 2011 IBM Corporation

  16. Useful MPIO Commands • List status of the paths and the parent device (or adapter) # lspath -Hl <hdisk#> • List connection information for a path # lspath -l hdisk2 -F"status parent connection path_status path_id“ Enabled fscsi0 203900a0b8478dda,f000000000000 Available 0 Enabled fscsi0 201800a0b8478dda,f000000000000 Available 1 Enabled fscsi1 201900a0b8478dda,f000000000000 Available 2 Enabled fscsi1 203800a0b8478dda,f000000000000 Available 3 • The connection field contains the storage port WWPN • In the case above, paths go to two storage ports and WWPNs:203900a0b8478dda 201800a0b8478dda • List a specific path's attributes # lspath -AEl hdisk2 -p fscsi0 –w “203900a0b8478dda,f00000000000“ scsi_id 0x30400 SCSI ID False node_name 0x200800a0b8478dda FC Node Name False priority 1 Priority True © 2011 IBM Corporation

  17. Path priorities • A Priority Attribute for paths can be used to specify a preference for path IOs. How it works depends whether the hdisk’s algorithm attribute is set to fail_over or round_robin. Value specified is inverse to priority, i.e. “1” is high priority • algorithm=fail_over • the path with the higher priority value handles all the IOs unless there's a path failure. • the other path(s) will only be used when there is a path failure. • Set the primary path to be used by setting it's priority value to 1, and the next path's priority (in case of path failure) to 2, and so on. • if the path priorities are the same and algorithm=fail_over, the primary path will be the first listed for the hdisk in the CuPath ODM as shown by # odmget CuPath • algorithm=round_robin • If the priority attributes are the same, then IOs go down each path equally. • In the case of two paths, if you set path A’s priority to 1 and path B’s to 255, then for every IO going down path A, there will be 255 IOs sent down path B. • To change the path priority of an MPIO device on a VIO client:#chpath -l hdisk0 -p vscsi1 -a priority=2 • Set path priorities for VSCSI disks to balance use of VIOSs  © 2011 IBM Corporation

  18. Path priorities # lsattr -El hdisk9 PCM PCM/friend/otherapdisk Path Control Module False algorithm fail_over Algorithm True hcheck_interval 60 Health Check Interval True hcheck_mode nonactive Health Check Mode True lun_id 0x5000000000000 Logical Unit Number ID False node_name 0x20060080e517b6ba FC Node Name False queue_depth 10 Queue DEPTH True reserve_policy single_path Reserve Policy True ww_name 0x20160080e517b6ba FC World Wide Name False … # lspath -l hdisk9 -F"parent connection status path_status" fscsi1 20160080e517b6ba,5000000000000 Enabled Available fscsi1 20170080e517b6ba,5000000000000 Enabled Available # lspath -AEl hdisk9 -p fscsi1 -w"20160080e517b6ba,5000000000000" scsi_id 0x10a00 SCSI ID False node_name 0x20060080e517b6ba FC Node Name False priority 1 Priority True Note: whether or not path priorities apply depends on the PCM. With SDDPCM, path priorities only apply when the algorithm used is fail over (fo). Otherwise, they aren’t used. © 2011 IBM Corporation

  19. Path priorities – why change them? • With VIOCs, send the IOs for half the LUNs to one VIOS and half to the other • Set priorities for half the LUNs to use VIOSa/vscsi0 and half to use VIOSb/vscsi1 • Uses both VIOSs CPU and virtual adapters • algorithm=fail_over is the only option at the VIOC for VSCSI disks • With NSeries – have the IOs go the primary controller for the LUN • Set via the dotpaths utility that comes with Nseries filesets © 2011 IBM Corporation

  20. Path Health Checking and Recovery • Validate a path is working • Automate recovery of path • For SDDPCM and MPIO compliant disks, two hdisk attributes apply: # lsattr -El hdisk26 hcheck_interval 0 Health Check Interval True hcheck_mode nonactive Health Check Mode True • hcheck_interval • Defines how often the health check is performed on the paths for a device. The attribute supports a range from 0 to 3600 seconds. When a value of 0 is selected (the default), health checking is disabled • Preferably set to at least 2X IO timeout value • hcheck_mode • Determines which paths should be checked when the health check capability is used: • enabled: Sends the healthcheck command down paths with a state of enabled • failed: Sends the healthcheck command down paths with a state of failed • nonactive: (Default) Sends the healthcheck command down paths that have no active I/O, including paths with a state of failed. If the algorithm selected is failover, then the healthcheck command is also sent on each of the paths that have a state of enabled but have no active IO. If the algorithm selected is round_robin, then the healthcheck command is only sent on paths with a state of failed, because the round_robin algorithm keeps all enabled paths active with IO. • Consider setting up error notification for path failures (later slide) © 2011 IBM Corporation

  21. Path Recovery • MPIO will recover failed paths if path health checking is enabled with hcheck_mode=nonactive or failedand the device has been opened • Trade-offs exist: • Lots of path health checking can create a lot of SAN traffic • Automatic recovery requires turning on path health checking for each LUN • Lots of time between health checks means paths will take longer to recover after repair • Health checking for a single LUN is often sufficient to monitor all the physical paths, but not to recover them • SDD and SDDPCM also recover failed paths automatically • In addition, SDDPCM provides a health check daemon to provide an automated method of reclaiming failed paths to a closed device. • To manually enable a failed path after repair or re-enable a disabled path: # chpath -l hdisk1 -p <parent> –w <connection> -s enable • To disable all paths using a specific FC port on the host: # chpath –l hdisk1 –p <parent> -s disable © 2011 IBM Corporation

  22. Path Health Checking and Recovery – Notification! • One should also set up error notification for path failure, so that someone knows about it and can correct it before something else fails. • This is accomplished by determining the error that shows up in the error log when a path fails (via testing), and then • Adding an entry to the errnotify ODM class for that error which calls a script (that you write) that notifies someone that a path has failed. Hint: You can use # odmget errnotify to see what the entries (or stanzas) look like, then you create a stanza and use the odmadd command to add it to the errnotify class. © 2011 IBM Corporation

  23. Path management with MPIO • Includes examining, adding, removing, enabling and disabling paths • Adapter failure/replacement or addition • VIOS upgrades (VIOS or multi-path code) • Cable failure and replacement • Storage controller/port failure and repair • Adapter replacement • Paths will not be in use if the adapter has failed, paths will be in the failed state • Remove paths with # rmpath –l <hdisk> -p <parent> -w <connection> [-d]-d will remove the path, without it the path will changed to Defined • Remove the adapter with # rmdev –Rdl <fcs#> • Replace the adapter • cfgmgr • Check the paths with lspath • It’s better to stop using a path before you know the path will disappear • Avoid timeouts, application delays or performance impacts and potential error recovery bugs © 2011 IBM Corporation

  24. Active/Active vs. Active/Passive Disk Subsystem Controllers • IOs for a LUN can be sent to any storage port with Active/Active controllers • LUNs are balanced across controllers for Active/Passive disk subsystems • So a controller is active for some LUNs, but passive for the others • IOs for a LUN are only sent to the Active controller’s port for disk subsystems with Active/Passive controllers • ESS, DS6000, DS8000, and XIV have active/active controllers • DS4000, DS5000, DS3950, Nseries, V7000 have active/passive controllers • The NSeries passive controller can accept IOs but IO latency is affected • The passive controller takes over in the event the active controller or all paths to it fail • MPIO recognizes Active/Passive disk subsystems and sends IOs only to the primary controller • Except under failure conditions, then the active/passive role switches for the affected LUNs • Terminology regaring active/active and active/passive varies considerably © 2011 IBM Corporation

  25. Example: Active/Passive Paths © 2011 IBM Corporation

  26. SDD: An Overview • SDD = Subsystem Device Driver – Pre-MPIO Architecture • Used with IBM ESS, DS6000, DS8000 and the SAN Volume Controller, but is not MPIO compliant • A “host attachment” fileset (provides subsystem-specific support code & populates the ODM) and SDD fileset are both installed • Host attachment: ibm2105.rte • SDD: devices.sdd.<sdd_version>.rte • LUNs show up as vpaths, with an hdisk device for each path • 32 paths maximum per LUN, but less are recommended with more than 600 LUNs • One installs SDDPCM or SDD, not both. • No support for rootvg, dump or paging devices • One can exclude disks from SDD control using theexcludesddcfg command • Mirror rootvg across two separate LUNs on different adapters for availability © 2011 IBM Corporation

  27. Load balancing algorithms fo: failover rr: round robin lb: load balancing (aka. df or the default) and chooses adapter with fewest in-flight IOs lbs: load balancing sequential – optimized for sequential IO rrs: round robin sequential – optimized for sequential IO The datapath command is used to examine vpaths, adapters, paths, vpath statistics, path statistics, adapter statistics, dynamically change the load balancing algorithm, and other administrative tasks such as adapter replacement, disabling paths, etc. mkvg4vp is used instead of mkvg, and extendvg4vp is used instead of extendvg SDD automatically recovers failed paths that have been repaired via the sddsrv daemon SDD © 2011 IBM Corporation

  28. Does Load Balancing Improve Performance? • Load balancing tried to reduce latency by picking a less active path • …but adds latency to choose the best path • These latencies are typically < 1% of typical IO service times • Load balancing is more likely to be of benefit in SANs with heavy utilizations or with intermittent errors that slow IOs on some path • A round_robin algorithm is usually equivalent Conclusion: Load balancing is unlikely to improve performance--especially when compared to other strategies like algorithm=round_robin or approaches that balance IO with algorithm=fail_over © 2011 IBM Corporation

  29. Balancing IOs with algorithm=fail_over • A fail_over algorithm can be efficiently used to balance IOs! • Any load_balancing algorithm must consume CPU and memory resources to determine the best path to use. • It's possible to setup fail_over LUNs so that the loads are balanced across the available FC adapters. • Let's use an example with 2 FC adapters. Assume we correctly lay out our data so that the IOs are balanced across the LUNs (this is usually a best practice). Then if we assign half the LUNs to FC adapterA and half to FC adapterB, then the IOs are evenly balanced across the adapters! • A question to ask is, “If one adapter is handling more IO than another, will this have a significant impact on IO latency?” • Since the FC adapters are capable of handling more than 35,000 IOPS then we're unlikely to bottleneck at the adapter and add significant latency to the IO. © 2011 IBM Corporation

  30. SDDPCM: An Overview • SDDPCM = Subsystem Device Driver Path Control Module • SDDPCM is MPIO compliant and can be used with IBM ESS, DS6000, DS8000, DS4000 (most models), DS5000, DS3950, V7000 and the SVC • A “host attachment” fileset (populates the ODM) and SDDPCM fileset are both installed • Host attachment: devices.fcp.disk.ibm.mpio.rte • SDDPCM: devices.sddpcm.<version>.rte • LUNs show up as hdisks, paths shown with pcmpath or lspath commands • 16 paths per LUN supported • Provides a PCM per the MPIO architecture • One installs SDDPCM or SDD, not both. SDDPCM is recommended and strategic © 2011 IBM Corporation

  31. Comparing AIX Default MPIO PCMs & SDDPCM © 2011 IBM Corporation

  32. SDDPCM • Load balancing algorithms • rr - round robin • lb - load balancing based on in-flight IOs per adapter • fo - failover policy • lbp - load balancing port(for ESS, DS6000, DS8000, V7000 and SVC only) based on in-flight IOs per adapter and per storage port • The pcmpath command is used to examine hdisks, adapters, paths, hdisk statistics, path statistics, adapter statistics, dynamically change the load balancing algorithm, and other administrative tasks such as adapter replacement, disabling paths • SDDPCM automatically recovers failed paths that have been repaired via the pcmserv daemon • MPIO health checking can also be used, and can be dynamically set via the pcmpath command. This is recommended. Set the hc_interval to a non-zero value for an appropriate number of LUNs to check the physical paths. © 2011 IBM Corporation

  33. Path management with SDDPCM and the pcmpath command # pcmpath query adapter # pcmpath query device # pcmpath query port # pcmpath query devstats # pcmpath query adaptstats # pcmpath query portstats # pcmpath query essmap # pcmpath set adapter … # pcmpath set device path … # pcmpath set device algorithm # pcmpath set device hc_interval # pcmpath disable/enable ports … # pcmpath query wwpn And more • SDD offers the similar datapath command List adapters and status List hdisks and paths List DS8000/DS6000/SVC… ports List hdisk/path IO statistics List adapter IO statistics List DS8000/DS6000/SVC port statistics List rank, LUN ID and more for each hdisk Disable/enable paths to adapter Disable/enable paths to a hdisk Dynamically change path algorithm Dynamically change health check interval Disable/enable paths to a disk port Display all FC adapter WWPNs © 2011 IBM Corporation

  34. Path management with SDDPCM and the pcmpath command # pcmpath query device … DEV#: 2 DEVICE NAME: hdisk2 TYPE: 2145 ALGORITHM: Load Balance SERIAL: 600507680190013250000000000000F4 ========================================================================== Path# Adapter/Path Name State Mode Select Errors 0 fscsi0/path0 OPEN NORMAL 40928736 0 1* fscsi0/path1 OPEN NORMAL 16 0 2 fscsi2/path4 OPEN NORMAL 43927751 0 3* fscsi2/path5 OPEN NORMAL 15 0 4 fscsi1/path2 OPEN NORMAL 44357912 0 5* fscsi1/path3 OPEN NORMAL 14 0 6 fscsi3/path6 OPEN NORMAL 43050237 0 7* fscsi3/path7 OPEN NORMAL 14 0 … • * Indicates path to passive controller • 2145 is a SVC which has active/passive nodes for a LUN • DS4000, DS5000, V7000 and DS3950 also have active/passive controllers • IOs will be balanced across paths to the active controller © 2011 IBM Corporation

  35. Path management with SDDPCM and the pcmpath command # pcmpath query devstats Total Dual Active and Active/Asymmetrc Devices : 67 DEV#: 2 DEVICE NAME: hdisk2 =============================== Total Read Total Write Active Read Active Write Maximum I/O: 169415657 2849038 0 0 20 SECTOR: 2446703617 318507176 0 0 5888 Transfer Size: <= 512 <= 4k <= 16K <= 64K > 64K 183162 67388759 35609487 46379563 22703724 … • Maximum value useful for tuning hdisk queue depths • “20” is maximum inflight requests for the IOs shown • Increase queue depth until queue is not filling up or until IO services times suffer (bottleneck is pushed to the subsystem) • writes > 3ms • reads > 15-20ms • See References for queue depth tuning whitepaper © 2011 IBM Corporation

  36. SDD & SDDPCM: Getting Disks configured correctly • Install the appropriate filesets • SDD or SDDPCM for the required disks (and host attachment fileset) • If you are using SDDPCM, install the MPIO fileset as well which comes with AIX • devices.common.IBM.mpio.rte • Host attachment scripts • http://www.ibm.com/support/dlsearch.wss?rs=540&q=host+scripts&tc=ST52G7&dc=D410 • Reboot or start the sddsrv/pcmsrv daemon • smitty disk -> List All Supported Disk • Displays disk types for which software support has been installed • Or # lsdev -Pc disk | grep MPIO disk mpioosdisk fcp MPIO Other FC SCSI Disk Drive disk 1750 fcp IBM MPIO FC 1750 …DS6000 disk 2105 fcp IBM MPIO FC 2105 …ESS disk 2107 fcp IBM MPIO FC 2107 …DS8000 disk 2145 fcp MPIO FC 2145 …SVC disk DS3950 fcp IBM MPIO DS3950 Array Disk disk DS4100 fcp IBM MPIO DS4100 Array Disk disk DS4200 fcp IBM MPIO DS4200 Array Disk disk DS4300 fcp IBM MPIO DS4300 Array Disk disk DS4500 fcp IBM MPIO DS4500 Array Disk disk DS4700 fcp IBM MPIO DS4700 Array Disk disk DS4800 fcp IBM MPIO DS4800 Array Disk disk DS5000 fcp IBM MPIO DS5000 Array Disk disk DS5020 fcp IBM MPIO DS5020 Array Disk © 2011 IBM Corporation

  37. www-01.ibm.com/support/docview.wss?rs=540&uid=ssg1S7001350#AIXSDDPCMwww-01.ibm.com/support/docview.wss?rs=540&uid=ssg1S7001350#AIXSDDPCM © 2011 IBM Corporation

  38. © 2011 IBM Corporation

  39. Migration from SDD to SDDPCM • Migration from SDD to SDDPCM is fairly straightforward and doesn't require a lot of time. The procedure is documented in the manual: • Varyoff your SDD VGs • Stop the sddsrv daemon via stopsrc -s sddsrv • Remove the SDD devices (both vpaths and hdisks) via instructions below • Remove the dpo device • Uninstall SDD and the host attachment fileset for SDD • Install the host attachment fileset for SDDPCM and SDDPCM • Configure the new disks (if you rebooted it's done, else run cfgmgr and startsrc –s pcmserv) • Varyon your VGs - you're back in business • To remove the vpaths and hdisks, use: • # rmdev -Rdl dpo • No exportvg/importvg is needed because LVM keeps track of PVs via PVID • Effective queue depths change (and changes to queue_depth will be lost): • SDD effective queue depth = # paths for a LUN x queue_depth • SDDPCM effective queue depth = queue_depth © 2011 IBM Corporation

  40. Multi-path code choices for DS4000/DS5000/DS3950 • These disk subsystems might use RDAC, MPIO or SDDPCM • Choices depend on model and AIX level • MPIO is strategic • SDDPCM uses MPIO and is recommended • SDDPCM not supported on VIOS yet for these disk subsystems so use MPIO • SAN cabling/zoning is more flexible with MPIO/SDDPCM than with RDAC • RDAC requires fcsA be connected to controllerA and fcsB connected to controllerB with no cross connections • These disk subsystems have active/passive controllers • All IO for a LUN goes to its primary controller • Unless the paths to it fail, or the controller fails, then the other controller takes over the LUN • Storage administrator assigns half the LUNs to each controller • The manage_disk_drivers command is used to choose the multi-path code • Choices vary among models and AIX levels • DS3950, DS5020, DS5100, DS5300 use MPIO or SDDPCM © 2011 IBM Corporation

  41. Multi-path code choices for DS3950, DS4000 and DS5000 # manage_disk_drivers -l Device Present Driver Driver Options 2810XIV AIX_AAPCM AIX_AAPCM,AIX_non_MPIO DS4100 AIX_SDDAPPCM AIX_APPCM,AIX_fcparray DS4200 AIX_SDDAPPCM AIX_APPCM,AIX_fcparray DS4300 AIX_SDDAPPCM AIX_APPCM,AIX_fcparray DS4500 AIX_SDDAPPCM AIX_APPCM,AIX_fcparray DS4700 AIX_SDDAPPCM AIX_APPCM,AIX_fcparray DS4800 AIX_SDDAPPCM AIX_APPCM,AIX_fcparray DS3950 AIX_SDDAPPCM AIX_APPCM DS5020 AIX_SDDAPPCM AIX_APPCM DS5100/DS5300 AIX_SDDAPPCM AIX_APPCM DS3500 AIX_AAPCM AIX_APPCM • To set the driver for use: # manage_disk_drivers -d <device> -o <driver_option> • AIX_AAPCM - MPIO with active/active controllers • AIX_APPCM - MPIO with active/passive controllers • AIX_SDDAPPCM - SDDPCM • AIX_fcparray - RDAC © 2011 IBM Corporation

  42. Other MPIO commands for DS3/4/5000 # mpio_get_config –Av Frame id 0: Storage Subsystem worldwide name: 608e50017be8800004bbc4c7e Controller count: 2 Partition count: 1 Partition 0: Storage Subsystem Name = 'DS-5020' hdisk LUN # Ownership User Label hdisk4 0 A (preferred) Array1_LUN1 hdisk5 1 B (preferred) Array2_LUN1 hdisk6 2 A (preferred) Array3_LUN1 hdisk7 3 B (preferred) Array4_LUN1 hdisk8 4 A (preferred) Array5_LUN1 hdisk9 5 B (preferred) Array6_LUN1 # sddpcm_get_config –Av output is the same as above © 2011 IBM Corporation

  43. XIV • Host Attachment Kit for AIXhttp://www-01.ibm.com/support/docview.wss?uid=ssg1S4000802 • # lsdev -Pc disk | grep xivdisk 2810xiv fcp N/A • XIV support has moved from fileset support, to support within AIX • Installing the Host Attachment Kit is still recommended  • Provides diagnostic and other commands  • Disks configured as 2810xiv devices  • ODM entries for XIV included with AIX 5.3 TL 10, AIX 6.1 TL3, VIOS 2.1.2.x and AIX 7 © 2011 IBM Corporation

  44. Nseries/NetApp • Nseries/NetApp has a preferred storage controller for each LUN • Not exactly an active/passive disk subsystem, as the non-preferred controller can accept IO requests • I/O requests have to be passed to the preferred controller which impacts latency • Install the SAN Toolkit Ontap.mpio_attach_kit.* • Provides the dotpaths utility and sanlun commands • dotpaths sets hdisk path priorities to favor the primary controller …for every IO going down secondary path, there will be 255 IOs sent down primary path © 2011 IBM Corporation

  45. Storage Area Network (SAN) Boot Boot from an SVC Storage is zoned directly to the client HBAs used for boot and/or data access SDDPCM runs in client (to support boot) Boot Directly from SAN Storage is zoned directly to the client HBAs used for boot and/or data access Multi-path code for the storage runs in client Boot from SVC via VIO Server Affected LUNs are zoned to VIOS(s) and assigned to clients via VIOS definitions Multi-path code in the client will be the MPIO default PCM for disks seen through the VIOS. SAN Sourced Boot Disks Affected LUNs are zoned to VIOS(s) and assigned to clients via VIOS definitions Multi-path code in the client will be the MPIO default PCM for disks seen through the VIOS. © 2011 IBM Corporation

  46. Storage Area Network (SAN) Boot • Requirements for SAN Booting • System with FC boot capability • Appropriate microcode (system, FC adapter, disk subsystem and FC switch) • Disk subsystem supporting AIX FC bootSome older systems don’t support FC boot, if in doubt, check the sales manual • SAN disk configuration • Create the SAN LUNs and assign them to the system's FC adapters’ WWPNs prior to installing the system • For non-MPIO configurations, assign one LUN to one WWPN to keep it simple • AIX installation • Boot from installation CD or NIM, this runs the install program • When you do the installation you'll get a list of disks that will be on the SAN for the system • Choose the disks for installing rootvg • Be aware of disk SCSI reservation policies • Avoid policies that limit access to a single path or adapter © 2011 IBM Corporation

  47. How to assure you install to the right SAN disk • Only assign the rootvg LUN to the host prior to install, assign data LUNs later, or • Create a LUN for rootvg with a size different than other LUNs, or • Write down LUN ID and storage WWN, or • Use disk with an existing PVIDThese criteria can be used to select the LUN from the AIX install program (shown in following screen shots) or via a bosinst_data file for NIM © 2011 IBM Corporation

  48. 1 hdisk2 U8234.EMA.06EF634-V5-C22-T1-W50050768012017C2-L1000000000000 2 hdisk3 U8234.EMA.06EF634-V5-C22-T1-W500507680120165C-L2000000000000 3 hdisk5 U8234.EMA.06EF634-V5-C22-T1-W500507680120165C-L3000000000000 Storage WWN LUN ID Choose via Location Code © 2011 IBM Corporation

  49. Choose via Size © 2011 IBM Corporation

  50. Choose via PVID © 2011 IBM Corporation

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