Tcm loop

The Linux SCSI Target Wiki

You do not have permission to edit this page, for the following reasons:

• The action you have requested is limited to users in the group: Administrators.
• This page has been locked to prevent editing.

You can view and copy the source of this page:

{{DISPLAYTITLE:tcm_loop}} {{Infobox software | name = LIO Linux SCSI Target | logo = [[Image:Corp_Logo.png|180px|Logo]] | screenshot = {{RTS screenshot|tcm_loop}} | caption = tcm_loop SCSI Emulation Device | collapsible = | author = {{Nicholas Bellinger}} | developer = {{RTS legal}} | released = {{RTS releases|tcm_loop|initial_date}} | discontinued = {{RTS releases|tcm_loop|eol_date}} | latest release version = {{RTS releases|tcm_loop|release_ver}} | latest release date = {{RTS releases|tcm_loop|release_date}} | latest preview version = {{RTS releases|tcm_loop|preview_ver}} | latest preview date = {{RTS releases|tcm_loop|preview_date}} | status = {{RTS releases|tcm_loop|status}} | frequently updated = | programming language = C | operating system = Linux | platform = | size = | language = | genre = Fabric module | license = GNU General Public License | website = {{RTS website}} }} :''See [[Target]] for a complete overview over all fabric modules.'' {{Image|TCM-KVM-Megasas-8708EM2-Windows7-x64.png|[[FILEIO]] with a tcm_loop SAS port on [[Kernel-based Virtual Machine|KVM]] x86_64 host running v2.6.34 with the new LSI Megasas 8708EM2 PPC HBA emulation into a Windows 7 x64 [[Kernel-based Virtual Machine|KVM]] Guest.}} <!-- {{Image|TCM Loop-OS2Warp-QEMU-KVM-HPFS.png|[[FILEIO]] with a tcm_loop SCSI port on [[Kernel-based Virtual Machine|KVM]] x86_64 host running v2.6.36-rc3+ with [[QEMU]] lsi53c895a HBA emulation into an OS/2 Warp v4 guest. A HPFS partition has been formatted and mounted as DRIVE D:.}} {{Image|TCM_Loop-3.2-RHEL5-NetBSD5.png|tcm_loop fabric module running on LIO v3.2 on a Linux Host providing shared virtual SAS Target emulation into a VM hypervisor to multiple VM guests of RHEL 5.4 x86_64 and NetBSD 5.x 32-bit.}} {{Image|TCM Loop-3.2-RHEL5-vmw6.png|tcm_loop fabric module running on LIO v3.2 on Linux Host v2.6.32-rc5 providing persistent reservations to RHEL 5.4 x86_64 [[Kernel-based Virtual Machine|KVM]] Guest using scsi generic passthrough with Vmware Workstation 6.5.}} --> '''tcm_loop''' is a fabric module that can emulate any supported fabric type locally for the Linux [[SCSI]] [[Target]]. == Overview == tcm_loop provides full local SCSI device emulation ([[SPC-3]] and [[SPC-4]]) for raw block storage objects. It thus makes any raw block device apear to the Linux SCSI [[Target]] as a full [[SPC-3]]/[[SPC-4]] [[SCSI]] compliant device with the corresponding [[CDB]]-level SAS emulation, for access from any SCSI LLD driver. tcm_loop minimizes overhead - it delivers >12&nbsp;GB/s (native) and >2&nbsp;GB/s (from a single [[Kernel-based Virtual Machine|KVM]] guest, without [http://en.wikipedia.org/wiki/Hardware-assisted_virtualization hardware assist]) on Intel [http://en.wikipedia.org/wiki/Nehalem_(microarchitecture) Nehalem] platforms. This provides e.g., unmodified guest operating systems, such as [[VMware ESX]] or [[VMware vSphere]], to use the full [[SPC-3]]/[[SPC-4]] [[SCSI]] functionality on any type of local raw block storage object they require. The tcm_loop fabric module ({{RTS releases|tcm_loop|module_repo}}, {{RTS releases|tcm_loop|module_info}}) for the Linux [[SCSI]] [[Target]] was released with Linux kernel {{RTS releases|tcm_loop|kernel_ver}} on {{RTS releases|tcm_loop|initial_date}}.<ref>{{RTS releases|tcm_loop|kernel_rel}}</ref> == targetcli == ''[[targetcli]]'' from {{RTS full}} is used to configure tcm_loop targets. ''targetcli'' aggregates service modules via a core library, and exports them through an API to the Linux SCSI [[Target]], to provide a unified single-node SAN configuration shell, independently of the underlying fabric(s). {{Ambox| type=info| head=RTS OS Admin Manual| text=The [[RTS OS]] [http://www.risingtidesystems.com/doc/RTS%20OS%20Admin%20Manual.pdf Admin Manual] provides comprehensive background and many examples on using ''targetcli'' and on programming the RTS library.}} === Startup === [[targetcli]] is invoked by running ''targetcli'' as root from the command prompt of the underlying OS shell. An initial setup as described in targetcli is assumed. <pre> # targetcli Welcome to targetcli: Copyright (c) 2013 by Datera, Inc. All rights reserved. Visit us at http://www.daterainc.com. Using ib_srpt fabric module. Using qla2xxx fabric module. Using iscsi fabric module. Using loopback fabric module. /> loopback/ info Fabric module name: loopback ConfigFS path: /sys/kernel/config/target/loopback Allowed WWN list type: naa Fabric module specfile: /var/target/fabric/loopback.spec Fabric module features: nexus Corresponding kernel module: tcm_loop /> </pre> === Cookbook === The following is a cheat sheet for reference purposes. {| class="table-left" |- bgcolor=#a0c0f0 ! Command ! Comment |- | ''/backstores/iblock create my_disk /dev/sdb'' | Create the LUN ''my_disk'' on the device ''/dev/sdb'' |- | In /backstores/iblock/my_disk>:<br/>''/loopback create'' | Create a local loopback target |- | ''/saveconfig'' | Commit the configuration |- |} === Display the object tree === Use ''ls'' to list the object hierarchy, which is initially empty: <pre> /> ls o- / ..................................................................... [...] o- backstores .......................................................... [...] | o- fileio ............................................... [0 Storage Object] | o- iblock ............................................... [0 Storage Object] | o- pscsi ................................................ [0 Storage Object] | o- rd_dr ................................................ [0 Storage Object] | o- rd_mcp ............................................... [0 Storage Object] o- ib_srpt ........................................................ [0 Target] o- iscsi .......................................................... [0 Target] o- loopback ....................................................... [0 Target] o- qla2xxx ........................................................ [0 Target] /> </pre> {{Ambox| type=info| head=Global parameter ''auto_cd_after_create''| text=After the creation of a new object, automatically enter its object context.}} Per default, ''auto_cd_after_create'' is set to ''true'', which automatically enters an object context (or working directory) after its creation. The examples here are modeled after this behavior. Optionally, set ''auto_cd_after_create=false'' to prevent ''targetcli'' from automatically entering new object contexts after their creation: <pre> /> set global auto_cd_after_create=false Parameter auto_cd_after_create is now 'false'. /> </pre> === Create a backstore === Create a backstore using the IBLOCK or FILEIO type devices. For instance, enter the top-level ''backstore'' context and create an IBLOCK backstore from a ''/dev/sdb'' block device: <pre> /> cd backstores/ /backstores> iblock/ create name=my_disk dev=/dev/sdb Generating a wwn serial. Created iblock storage object my_disk using /dev/sdb. Entering new node /backstores/iblock/my_disk. /backstores/iblock/my_disk> </pre> ''targetcli'' automatically creates a WWN serial ID for the backstore device and then changes the working context to it. The resulting object hierarchy looks as follows (displayed from the root object): <pre> /> ls o- / ..................................................................... [...] o- backstores .......................................................... [...] | o- fileio ............................................... [0 Storage Object] | o- iblock ............................................... [1 Storage Object] | | o- my_disk .......................................... [/dev/sdb activated] | o- pscsi ................................................ [0 Storage Object] | o- rd_dr ................................................ [0 Storage Object] | o- rd_mcp ............................................... [0 Storage Object] o- ib_srpt ........................................................ [0 Target] o- iscsi .......................................................... [0 Target] o- loopback ....................................................... [0 Target] o- qla2xxx ........................................................ [0 Target] /> </pre> Alternatively, any LVM logical volume can be used as a backstore, please refer to the [http://www.risingtidesystems.com/doc/RTS%20OS%20Admin%20Manual.pdf RTS OS Admin Manual] on how to create them properly. For instance, create an IBLOCK backstore on a logical volume (under ''/dev/<volume_group_name>/<logical_volume_name>''): <pre> /backstores> iblock/ create name=my_disk dev=/dev/vg0/lv1 Generating a wwn serial. Created iblock storage object my_disk using /dev/vg0/lv1. Entering new node /backstores/iblock/my_disk. /backstores/iblock/my_disk> </pre> Again, ''targetcli'' automatically creates a WWN serial ID for the backstore device and then changes the working context to it. {{Ambox| type=info| head=More backstore examples| text=More examples on creating backstores can be found in ''[[targetcli#Create a backstore|targetcli]]''.}} === Instantiate a target === Instantiate a loopback target on the existing IBLOCK backstore device ''my_disk'' (as set up in [[targetcli]]): <pre> /backstores/iblock/my_disk> /loopback create Successfully created LUN 0. Entering new node /loopback/naa.60014057f822d991/luns/lun0. /loopback/naa...991/luns/lun0> </pre> ''targetcli'' automatically assigns the default ID '0' to the LUN, and then changes the working context to the new LUN. Now the target is created, and exports ''/dev/sdb'' as LUN 0. Return to the root context, as no attributes need to be set or modified for a standard loopback target: <pre> /loopback/naa...991/luns/lun0> cd / /> </pre> === Display the object tree === The resulting object hierarchy looks as follows (displayed from the root object): <pre> /> ls o- / ..................................................................... [...] o- backstores .......................................................... [...] | o- fileio ............................................... [0 Storage Object] | o- iblock ............................................... [1 Storage Object] | | o- my_disk .......................................... [/dev/sdb activated] | o- pscsi ................................................ [0 Storage Object] | o- rd_dr ................................................ [0 Storage Object] | o- rd_mcp ............................................... [0 Storage Object] o- ib_srpt ........................................................ [0 Target] o- iscsi .......................................................... [0 Target] o- loopback ....................................................... [1 Target] | o- naa.60014057f822d991 ............................. [naa.60014053485b9490] | | o- luns .......................................................... [1 LUN] | | o- lun0 .................................... [iblock/my_disk (/dev/sbd)] o- qla2xxx ........................................................ [0 Target] /> </pre> === Persist the configuration === {{Ambox| type=warning| head=Don't forget to use ''saveconfig''!| text=Without ''saveconfig'', the target configuration will be lost upon rebooting or unloading the target service, as the target configuration will revert back to the last saved one.}} Use ''saveconfig'' from the root context to persist the target configuration across OS reboots: <pre> /> saveconfig WARNING: Saving rtsnode1 current configuration to disk will overwrite your boot settings. The current target configuration will become the default boot config. Are you sure? Type 'yes': yes Making backup of srpt/ConfigFS with timestamp: 2012-02-27_23:19:37.660264 Successfully updated default config /etc/target/srpt_start.sh Making backup of qla2xxx/ConfigFS with timestamp: 2012-02-27_23:19:37.660264 Successfully updated default config /etc/target/qla2xxx_start.sh Making backup of loopback/ConfigFS with timestamp: 2012-02-27_23:19:37.660264 Successfully updated default config /etc/target/loopback_start.sh Making backup of LIO-Target/ConfigFS with timestamp: 2012-02-27_23:19:37.660264 Successfully updated default config /etc/target/lio_backup-2012-02-27_23:19:37.660264.sh Making backup of Target_Core_Mod/ConfigFS with timestamp: 2012-02-27_23:19:37.660264 Successfully updated default config /etc/target/tcm_backup-2012-02-27_23:19:37.660264.sh Generated Target_Core_Mod config: /etc/target/backup/tcm_backup-2012-02-27_23:19:37.660264.sh Successfully updated default config /etc/target/lio_start.sh Successfully updated default config /etc/target/tcm_start.sh /> </pre> === Spec file === RTS spec files define the fabric-dependent feature set, capabilities and available target ports of the specific underlying fabric. In particular, the tcm_loop spec file ''/var/target/fabric/loopback.spec'' is included via RTSlib. <pre> # WARNING: This is a draft specfile supplied for demo purposes only. # The loopback fabric module uses the default feature set features = nexus # Use naa WWNs wwn_type = naa # Non-standard module naming scheme kernel_module = tcm_loop # The configfs group configfs_group = loopback </pre> == Specifications == The type of SCSI fabric features that are available with tcm_loop (Target mode emulated SAS ports) includes the complete set of SPC-3/SPC-4 logic in the Linux SCSI [[Target]] engine including advanced features such as [[PRs]], [[ALUA]], etc. tcm_loop supports high level fabric emulation. That is, depending on which [[WWN]] is used to create the [[ConfigFS]] group in ''/sys/kernel/config/target/loopback/$WWN'', it configures itself to return iSCSI, FC etc. device identifiers for the SCSI LUN protocol identifiers device identifier page. == See also == * [[RTS OS]], [[targetcli]] * Linux [[SCSI]] [[Target]] * [[Fibre Channel]], [[Fibre Channel over Ethernet|FCoE]], [[iSCSI]], [[iSER]], [[SRP]], [[vHost]] * [[ConfigFS]] (low level kernel API) == Notes == {{Reflist}} == External links == * {{Official|http://www.daterainc.com Datera}} * [[RTS OS]] [http://www.risingtidesystems.com/doc/RTS%20OS%20Admin%20Manual.pdf Admin Manual] * RTSlib Reference Guide [[http://www.risingtidesystems.com/doc/rtslib-gpl/html/ HTML]][[http://www.risingtidesystems.com/doc/rtslib-gpl/pdf/rtslib-API-reference.pdf PDF]] {{LIO Timeline}} [[Category:Fabric modules]] [[Category:SCSI]] [[Category:Virtualization]]

Return to Tcm loop.