The Host Server. Citrix XenServer Configuration Guide. November The Data Infrastructure Software Company

Transcription

1 The Host Server Citrix XenServer Configuration Guide November 2017 This guide provides configuration settings and considerations for SANsymphony Hosts running Citrix XenServer. Basic Citrix XenServer administration skills are assumed including how to connect to iscsi and/or Fibre Channel Storage Array target ports as well as the processes of discovering, mounting and formatting a disk device. The Data Infrastructure Software Company

2 Table of contents Changes made to this document 3 XenServer compatibility list 4 The DataCore Server's settings 6 The XenServer Host's settings 8 XenServer 7.x 8 XenServer 6.x 10 Known issues 12 XenServer 7.x 13 XenServer 6.x 14 Appendix A 15 Preferred Server & Preferred Path settings 15 Appendix B 17 Configuring Disk Pools 17 Appendix C 18 Reclaiming storage 18 Previous changes 21 Page 2

3 Changes made to this document The most recent version of this document is available from here: All changes since May 2017 Updated XenServer compatibility list XenServer 7.2 is now Qualified with SANsymphony-V 10.x with or without ALUA. All previous changes Please see page 21 Page 3

4 XenServer compatibility list SANsymphony 9.0 PSP4 Update 4 (1) Version 10.0 (all versions) Version With ALUA Without ALUA With ALUA Without ALUA 6.0 or earlier Not Supported Not Supported Not Supported Not Supported 6.1 Qualified (2) Qualified Not Qualified Not Qualified 6.2 Not Qualified Not Qualified Not Qualified Not Qualified 6.5 Not Qualified Not Qualified Qualified (2) Qualified 7.0 Not Supported Not Supported Qualified Qualified 7.1 Not Supported Not Supported Qualified Qualified 7.2 Not Supported Not Supported Qualified Qualified Notes: Qualified vs. Not Qualified vs. Not Supported See the next page for definitions. DataCore Server Front-End Port connections Fibre Channel and iscsi connections are supported. SCSI UNMAP SCSI UNMAP is only supported with SANsymphony 10.0 PSP 6 and greater. For earlier versions SCSI UNMAP does not work. Reclaiming storage from DataCore Disk Pools See Appendix C: 'Reclaiming Storage' on page Error! Bookmark not defined. for version-specific 'how to' instructions. 1 SANsymphony-V 8.x and all versions of SANsymphony 9.x before PSP4 Update 4 are now End of Life. Please see: End of Life Notifications 2 iscsi Front End connections only. Page 4

5 Qualified vs. Not Qualified vs. Not Supported Qualified This combination has been tested by DataCore and all the host-specific settings listed in this document applied using non-mirrored, mirrored and Dual Virtual Disks. Not Qualified This combination has not yet been tested by DataCore using Mirrored or Dual Virtual Disks types. DataCore cannot guarantee 'high availability' (failover/failback, continued access etc.) even if the host-specific settings listed in this document are applied. Self-qualification may be possible please see Technical Support FAQ #1506 Mirrored or Dual Virtual Disks types are configured at the users own risk; however, any problems that are encountered while using XenServer versions that are 'Not Qualified' will still get root-cause analysis. Non-mirrored Virtual Disks are always considered 'Qualified' - even for 'Not Qualified' combinations of XenServer/SANsymphony. Not Supported This combination has either failed 'high availability' testing by DataCore using Mirrored or Dual Virtual Disks types; or the operating System's own requirements/limitations (e.g. age, specific hardware requirements) make it impractical to test. DataCore will not guarantee 'high availability' (failover/failback, continued access etc.) if the host-specific settings listed in this document are applied. Mirrored or Dual Virtual Disks types are configured at the users own risk. Self-qualification is not possible. Mirrored or Dual Virtual Disks types are configured at the users own risk; however, any problems that are encountered while using XenServer versions that are 'Not Supported' will get best-effort Technical Support (e.g. to get access to Virtual Disks) but no root-cause analysis will be done. Non-mirrored Virtual Disks are always considered 'Qualified' even for 'Not Supported' combinations of XenServer/SANsymphony. Citrix XenServer versions that are End of Life (EOL) For versions that are listed as 'Not Supported', self-qualification is not possible. For versions that are listed as 'Not Qualified', self-qualification may be possible if there is an agreed support contract with Citrix as well. Please contact DataCore Technical Support before attempting any self-qualification. For any problems that are encountered while using XenServer versions that are EOL with DataCore Software, only best-effort Technical Support will be performed (e.g. to get access to Virtual Disks). Root-cause analysis will not be done. Non-mirrored Virtual Disks are always considered 'Qualified'. Page 5

6 The DataCore Server's settings Operating System Type When registering the Host for the first time, choose the 'Citrix XenServer' menu option. Also see the Registering Hosts section from the SANsymphony Help: Port roles Ports used for serving Virtual Disks to Hosts should only have the Front End (FE) role enabled. Mixing other Port Role types may cause unexpected results as Ports that only have the FE role enabled will be turned off when the DataCore Server software is stopped (even if the physical server remains running). This helps to guarantee that any Hosts do not still try to access FE Ports, for any reason, once the DataCore Software is stopped but where the DataCore Server remains running. Any Port with the Mirror and/or Back End role enabled do not shut off when the DataCore Server software is stopped but still remain active. Multipathing support The Multipathing Support option should be enabled so that Mirrored Virtual Disks or Dual Virtual Disks can be served to Hosts from all available DataCore FE ports. Also see the Multipathing Support section from the SANsymphony Help: Webhelp/Hosts.htm Non-mirrored Virtual Disks and Multipathing Non-mirrored Virtual Disks can still be served to multiple Hosts and/or multiple Host Ports from one or more DataCore Server FE Ports if required; in this case the Host can use its own multipathing software to manage the multiple Host paths to the Single Virtual Disk as if it was a Mirrored or Dual Virtual Disk. Note: Hosts that have non-mirrored Virtual Disks served to them do not need Multipathing Support enabled unless they have other Mirrored or Dual Virtual Disks served as well. Asymmetrical Logical Unit Access (ALUA) support The ALUA support option should be enabled if required and if Multipathing Support has been also been enabled (see above). Please refer to the compatibility list on page 4 to see which versions of Citrix XenServer can be used with either Fibre Channel or iscsi ports when using ALUA. More information on Preferred Servers and Preferred Paths used by the ALUA function can be found on in Appendix A on page 15. Page 6

7 The DataCore Server's settings Serving Virtual Disks to the Hosts for the first time DataCore recommends that before serving Virtual Disks for the first time to a Host, that all DataCore Front-End ports on all DataCore Servers are correctly discovered by the Host first. Then, from within the SANsymphony Console, the Virtual Disk is marked Online, up to date and that the storage sources have a host access status of Read/Write. Virtual Disks LUNs and serving to more than one Host or Port DataCore Virtual Disks always have their own unique Network Address Authority (NAA) identifier that a Host can use to manage the same Virtual Disk being served to multiple Ports on the same Host Server and the same Virtual Disk being served to multiple Hosts. See the SCSI Standard Inquiry Data section from the online Help for more information on this: While DataCore cannot guarantee that a disk device's NAA is used by a Host's operating system to identify a disk device served to it over different paths generally we have found that it is. And while there is sometimes a convention that all paths by the same disk device should always using the same LUN 'number' to guarantees consistency for device identification, this may not be technically true. Always refer to the Host Operating System vendor s own documentation for advice on this. DataCore's Software does, however always try to create mappings between the Host's ports and the DataCore Server's Front-end (FE) ports for a Virtual Disk using the same LUN number (1) where it can. The software will first find the next available (lowest) LUN 'number' for the Host- DataCore FE mapping combination being applied and will then try to apply that same LUN number for all other mappings that are being attempted when the Virtual Disk is being served. If any Host-DataCore FE port combination being requested at that moment is already using that same LUN number (e.g. if a Host has other Virtual Disks served to it from previous) then the software will find the next available LUN number and apply that to those specific Host- DataCore FE mappings only. 1 The software will also try to match a LUN 'number' for all DataCore Server Mirror Port mappings of a Virtual Disk too, although the Host does not 'see' these mirror mappings and so this does not technically need to be the same as the Front End port mappings (or indeed as other Mirror Path mappings for the same Virtual Disk). Having Mirror mappings using different LUNs has no functional impact on the Host or DataCore Server at all. Page 7

8 The XenServer Host's settings XenServer 7.x Multipath Configuration Settings Polling Interval In the defaults section of the multipath.conf file, the polling_interval must be set to 10 defaults { } polling_interval 10 This is a DataCore-required value which helps prevent excessive Host attempts to check for a Virtual Disk Storage Source s Host Access value, after a failure, is set as Offline. Smaller interval settings will interfere with overall Host performance. Do not add this parameter to the 'device' section (discussed on the next page) by mistake; else the setting will not work as expected. The 'device' section ALUA-enabled Hosts This is qualified for both Fibre Channel and iscsi connections. device { vendor "DataCore" product "Virtual Disk" path_checker tur failback 30 path_selector "round-robin 0" rr_min_io 100 path_grouping_policy group_by_prio prio alua } Page 8

9 Multipath Configuration Settings for XenServer 7.x continued Without ALUA enabled This is qualified for both Fibre Channel and iscsi connections. The XenServer Host's settings device { } vendor "DataCore" product "Virtual Disk" path_checker tur failback 10 path_grouping_policy failover prio hp_sw Device section notes Note: All entries listed are required by SANsymphony and are case sensitive. failback This adds an extra wait period (10 seconds) that helps to prevent unnecessary failback attempts to a Virtual Disk whose Storage Source s Host Access value is still set as Not Allowed. path_checker This is a DataCore-required value. No other value should be used. path_grouping_policy group_by_prio or path_grouping_policy group_by_failover One of two possible values is required depending if you are using ALUA or not group_by_prio or failover - to avoid any other, non-datacore, setting in the multipath.conf (i.e. from other storage arrays attached to the XenServer Host) from taking precedence. In either case, make sure the Preferred Server setting on the DataCore Server is either set to 'Auto Select' or an explicit Server Name. See Appendix A on page 15 about information regarding the 'Auto Select' setting. prio This is a DataCore-required value. Note that for non-alua the 'hp_sw' switch was required to get failover and failback working correctly during DataCore's qualification tests for XenServer 7.x. rr_min_io (ALUA only) This is a DataCore-required value. Page 9

10 The XenServer Host's settings XenServer 6.x Multipath Configuration Settings Polling Interval In the defaults section of the multipath.conf file, the polling_interval must be set to 10 defaults { } polling_interval 10 This is a DataCore-required value which helps prevent excessive Host attempts to check for a Virtual Disk Storage Source s Host Access value, after a failure, is set as Offline. Smaller interval settings will interfere with overall Host performance. Do not add this parameter to the 'device' section (discussed on the next page) by mistake; else the setting will not work as expected. The 'device' section ALUA-enabled Hosts This is qualified for iscsi connections only. device { vendor "DataCore" product "Virtual Disk" path_checker tur failback 30 path_selector "round-robin 0" rr_min_io 100 path_grouping_policy group_by_prio # Comment out if using Citrix XenServer 6.1 or earlier prio alua # Uncomment if using Citrix XenServer 6.1 or earlier # prio_callout "/sbin/mpath_prio_alua %d" } Page 10

11 Multipath Configuration Settings for XenServer 6.x continued Without ALUA enabled This is qualified for both Fibre Channel and iscsi connections. The XenServer Host's settings device { } vendor "DataCore" product "Virtual Disk" path_checker tur failback 10 path_grouping_policy failover Device section notes Note: All entries listed are required by SANsymphony and are case sensitive. failback This adds an extra wait period (10 seconds) that helps to prevent unnecessary failback attempts to a Virtual Disk whose Storage Source s Host Access value is still set as Not Allowed. path_checker This is a DataCore-required value. No other value should be used. path_grouping_policy group_by_prio or path_grouping_policy group_by_failover One of two possible values is required depending if you are using ALUA or not group_by_prio or failover - to avoid any other, non-datacore, setting in the multipath.conf (i.e. from other storage arrays attached to the XenServer Host) from taking precedence. In either case, make sure the Preferred Server setting on the DataCore Server is either set to 'Auto Select' or an explicit Server Name. See Appendix A on page 15 about information regarding the 'Auto Select' setting. rr_min_io This is a DataCore-required value. Page 11

12 Known issues The following is intended to make DataCore Software customers aware of any issues that may affect performance, access or generally give unexpected results under certain conditions when XenServer Hosts are used with SANsymphony. Some of the issues here have been found during DataCore s own testing but many others are issues reported by DataCore Software customers, where a specific problem had been identified and then subsequently resolved. DataCore cannot be held responsible for incorrect information regarding Citrix products. No assumption should be made that DataCore has direct communication with Citrix regarding the issues listed here and we always recommend that users contact Citrix directly to see if there are any updates or fixes since they were reported to us. For Known issues for DataCore s own Software products, please refer to the relevant DataCore Software Component s release notes. Page 12

13 Known issues XenServer 7.x Hardware QLogic QLA405x/406x iscsi HBAs Use QLogic s Firmware revision or greater General Virtual Disks must be served to both the XenServer pool master as well as its members to be discovered as pool member operations always go 'via' the XenServer 'Master' Server. For example, if a XenServer Pool member has Virtual Disk 1 served to it but the Master Server does not (or vice versa), then XenServer will never discover Virtual Disk 1 when scanning for it. XenServer may not detect new size changes from a previously served Virtual Disk Even if a Storage Repository (SR) is destroyed (and the Virtual Disk(s) are unserved); any subsequent change to a Virtual Disk's size will not be re-detected when it is then served back to the same XenServer Host. In this case the previous Virtual Disk size will be reported. The multipath.conf file may get overwritten when upgrading After upgrading from an older version of XenServer, always check that the upgrade has not overwritten changes made to the multipath.conf file. Depending on the version of XenServer, multipath.conf may be a soft link that points to /etc/multipath-enabled.conf. Note that it is usually not enough to simply save a copy of this file and reapply it after the upgrade without a further reboot contact Citrix for more advice. Page 13

14 Known issues XenServer 6.x Hardware QLogic QLA405x/406x iscsi HBAs Use QLogic s Firmware revision or greater General Virtual Disks must be served to both the XenServer pool master as well as its members to be discovered as pool member operations always go 'via' the XenServer 'Master' Server. For example, if a XenServer Pool member has Virtual Disk 1 served to it but the Master Server does not (or vice versa), then XenServer will never discover Virtual Disk 1 when scanning for it. XenServer may not detect new size changes from a previously served Virtual Disk Even if a Storage Repository (SR) is destroyed (and the Virtual Disk(s) are unserved); any subsequent change to a Virtual Disk's size will not be re-detected when it is then served back to the same XenServer Host. In this case the previous Virtual Disk size will be reported. The multipath.conf file may get overwritten when upgrading After upgrading from an older version of XenServer, always check that the upgrade has not overwritten changes made to the multipath.conf file. Depending on the version of XenServer, multipath.conf may be a soft link that points to /etc/multipath-enabled.conf. Note that it is usually not enough to simply save a copy of this file and reapply it after the upgrade without a further reboot contact Citrix for more advice. Hotfixes A hotfix is required for XenServer when using space TRIM/UNMAP commands on Virtual Disks that are larger than 2TB In XenCenter, this feature is labelled 'Reclaim freed space' on the Xen host's Storage tab. Downloaded from here: Note that running TRIM/UNMAP commands is only qualified with Virtual Disks served from SANsymphony 10.0 PSP 6 or greater. Please see Appendix C on page 17 for more details. A hotfix is required for XenServer when using iscsi FE Ports Downloaded from here: A hotfix is required for XenServer when using iscsi FE Ports Downloaded from here: Page 14

15 Appendix A Preferred Server & Preferred Path settings See the Preferred Servers and Preferred Paths sections from the SANsymphony Help: Without ALUA enabled Note: Asymmetrical Logical Unit Access (ALUA) is only qualified with iscsi connections. If Hosts are registered without ALUA support, the Preferred Server and Preferred Path settings will serve no function. All DataCore Servers and their respective Front End (FE) paths are considered equal. It is up to the Host s own Operating System or Failover Software to determine which DataCore Server is its preferred server. With ALUA enabled Setting the Preferred Server to Auto (or an explicit DataCore Server), determines the DataCore Server that is designated Active Optimized for Host IO. The other DataCore Server is designated Active Non-Optimized. If for any reason the Storage Source on the preferred DataCore Server becomes unavailable, and the Host Access for the Virtual Disk is set to Offline or Disabled, then the other DataCore Server will be designated the Active Optimized side. The Host will be notified by both DataCore Servers that there has been an ALUA state change, forcing the Host to re-check the ALUA state of both DataCore Servers and act accordingly. If the Storage Source on the preferred DataCore Server becomes unavailable but the Host Access for the Virtual Disk remains Read/Write, for example if only the Storage behind the DataCore Server is unavailable but the FE and MR paths are all connected or if the Host physically becomes disconnected from the preferred DataCore Server (e.g. Fibre Channel or iscsi Cable failure) then the ALUA state will not change for the remaining, Active Nonoptimized side. However, in this case, the DataCore Server will not prevent access to the Host nor will it change the way READ or WRITE IO is handled compared to the Active Optimized side, but the Host will still register this DataCore Server s Paths as Active Non-Optimized which may (or may not) affect how the Host behaves generally. Page 15

16 Appendix A Preferred Server & Preferred Path settings In the case where the Preferred Server is set to All, then both DataCore Servers are designated Active Optimized for Host IO. All IO requests from a Host will use all Paths to all DataCore Servers equally, regardless of the distance that the IO has to travel to the DataCore Server. For this reason, the All setting is not normally recommended. If a Host has to send a WRITE IO to a remote DataCore Server (where the IO Path is significantly distant compared to the other local DataCore Server), then the WAIT times accrued by having to send the IO not only across the SAN to the remote DataCore Server, but for the remote DataCore Server to mirror back to the local DataCore Server and then for the mirror write to be acknowledged from the local DataCore Server to the remote DataCore Server and finally for the acknowledgement to be sent to the Host back across the SAN, can be significant. The benefits of being able to use all Paths to all DataCore Servers for all Virtual Disks are not always clear cut. Testing is advised. For Preferred Path settings it is stated in the SANsymphony Help: A preferred front-end path setting can also be set manually for a particular virtual disk. In this case, the manual setting for a virtual disk overrides the preferred path created by the preferred server setting for the host. So for example, if the Preferred Server is designated as DataCore Server A and the Preferred Paths are designated as DataCore Server B, then DataCore Server B will be the Active Optimized Side not DataCore Server A. In a two-node Server group there is usually nothing to be gained by making the Preferred Path setting different to the Preferred Server setting and it may also cause confusion when trying to diagnose path problems, or when redesigning your DataCore SAN with regard to Host IO Paths. For Server Groups that have three or more DataCore Servers, and where one (or more) of these DataCore Servers shares Mirror Paths between other DataCore Servers setting the Preferred Path makes more sense. So for example, DataCore Server A has two mirrored Virtual Disks, one with DataCore Server B, and one with DataCore Server C and DataCore Server B also has a mirrored Virtual Disk with DataCore Server C then using just the Preferred Server setting to designate the Active Optimized side for the Host s Virtual Disks becomes more complicated. In this case the Preferred Path setting can be used to override the Preferred Server setting for a much more granular level of control. Page 16

17 Appendix B Configuring Disk Pools See Creating Disk Pools and Adding Physical Disks from the SANsymphony Help: The smaller the SAU size, the larger the number of indexes are required, by the Disk Pool driver, to keep track of the equivalent amount of allocated storage compared to a Disk Pool with a larger SAU size; e.g. there are potentially four times as many indexes required in a Disk Pool using a 32MB SAU size compared to one using 128MB the default SAU size. As SAUs are allocated for the very first time, the Disk Pool needs to update these indexes and this may cause a slight delay for IO completion and might be noticeable on the Host. However this will depend on a number of factors such as the speed of the physical disks, the number of Hosts accessing the Disk Pool and their IO READ/WRITE patterns, the number of Virtual Disks in the Disk Pool and their corresponding Storage Profiles. Therefore, DataCore usually recommend using the default SAU size (128MB) as it is a good compromise between physical storage allocation and IO overhead during the initial SAU allocation index update. Should a smaller SAU size be preferred, the configuration should be tested to make sure that a potential increased number of initial SAU allocations does not impact the overall Host performance. Page 17

18 Appendix C Reclaiming storage Using SCSI UNMAP commands to reclaim storage As of SANsymphony-V 10.0 PSP 6 there is support for SCSI UNMAP commands which allows Hosts to send 'all-zero' write I/O to a Virtual Disk and trigger SANsymphony's Automatic Reclamation feature. See below. Please refer to Citrix's own documentation on how to configure XenServer Hosts for SCSI UNMAP use For Citrix XenServer hosts that do not support SCSI UNMAP or that are connected to DataCore Servers that are using earlier versions of SANsymphony, see the following section below 'Using the 'Automatic Reclamation' feature with 'manual zeroing' of a Virtual Machine's own filesystem to reclaim storage' SANsymphony's Automatic Reclamation feature DataCore Servers keep track of any 'all-zero' write I/O requests sent to Storage Allocation Units (SAU) in all Disk Pools. When enough 'all-zero' writes have been detected to have been passed down to an entire SAUs logical address space, that SAU will be immediately assigned as 'free' (as if it had been manually reclaimed) and made available to the entire Disk Pool for future (re)use. No additional 'zeroing' of the Physical Disk or 'scanning' of the Disk Pool is required. Important technical notes on Automatic Reclamation The Disk Pool driver has a small amount of system memory that it uses keep a list of all address spaces in a Disk Pool that are sent 'all-zero' writes; all other (non-zero) write requests are ignored by the Automatic Reclamation feature and not included in the in-memory list. Any all-zero write addresses that are detected to be physically 'adjacent' to each other from a block address point of view the Disk Pool driver will 'merge' these requests together in the list so as to keep the size of it as small as possible. Also as entire 'all-zeroed' SAUs are re-assigned back to the Disk Pool, the record of all its address spaces is removed from the in-memory list making space available for future all-zero writes to other SAUs that are still allocated. However if write I/O pattern of the Hosts mean that the Disk Pool receives all-zero writes to many, non-adjacent block addresses the list will require more space to keep track of them compared to all-adjacent block addresses. In extreme cases, where the in-memory list can no longer hold any more new all-zero writes (because all the allocated system memory for the Page 18

19 Appendix C Reclaiming storage Automatic Reclamation feature has been used) the Disk Pool driver will discard the oldest records of the all-zero writes to accommodate newer records of all-zero write I/O. Likewise if a DataCore Server is rebooted for any reason, then the in-memory list is completely lost and any knowledge of SAUs that were already partially detected as having been written with all-zeroes will now no longer be remembered. In both of these cases this can mean that, over time, even though technically an SAU may have been completely overwritten with all-zero writes, the Disk Pool driver does not have a record that cover the entire address space of that SAU in its in-memory list and so the SAU will not be made available to the Disk Pool but remain allocated to the Virtual Disk until any future all-zero writes happen to re-write the same address spaces that were forgotten about previously by the Disk Pool driver. In these scenarios, a Manual Reclamation will force the Disk Pool to re-read all SAUs and perhaps detect those now missing all-zero address spaces. See the section 'Manual Reclamation' on the next page for more information. Reclaiming storage by sending all-zero writes to a Virtual Machine's own filesystem A suggestion would be create a raw VDI on the storage repository and format it using the 'vdicreate' command. For example: xe vdi-create sr-uuid={datacore-sr-uuid} type=user virtual-size=50gib / name-label=reclaimdisk sm-config:type=raw Present the VDI device to an existing virtual machine running on the XenServer Host and then, from within the VM's own operating system, issue 'zeroes' to the VDI disk device. For VMs using Windows file systems (NTFS/FAT), one suggestion is to use the Microsoft s sdelete tool. For Unix/Linux-based Hosts, use the dd command to fill all of the unused file system space with 'all-zero' write I/O. For example: if=/dev/zero of=/myemptyfile This I/O will then be detected by SANsymphony's Automatic Reclamation function (see previous page for more details). See the Performing Reclamation section from the SANsymphony Help: Page 19

20 Appendix C Reclaiming storage SANsymphony's Manual Reclamation feature Manual reclamation forces the Disk Pool driver to 'read' all SAUs currently assigned to a Virtual Disk looking for SAUs that contain only all-zero IO data. Once detected, that SAU will be immediately assigned as 'free' and made available to the entire Disk Pool for future (re)use. No additional 'zeroing' of the Physical Disk is required. Note that manual reclamation will create additional 'read' I/O on the Storage Array used by the Disk Pool, as this process runs at 'low priority' it should not interfere with normal I/O operations. However, caution is advised, especially when scripting the manual reclamation process. Manual Reclamation may still be required even when Automatic Reclamation has taken place (see the 'Automatic Reclamation' section on the previous page for more information) How much storage will actually be reclaimed? It is impossible to predict exactly how many Storage Allocation Units (SAUs) will be reclaimed. For reclamation of an SAU to take place, it must contain only all-zero block data over the entire SAU else it will remain allocated and this is entirely dependent on how and where the Host has written its data on the DataCore LUN. For example, if the Host has written the data in such a way that every allocated SAU contains a small amount of non-zero block data then no (or very few) SAUs can be reclaimed, even if the total amount of data is much less than the total amount of assigned SAUs. It may be possible to use the Host operating system s own defragmentation tools to move andy data that is spread out over the DataCore LUN so that it ends up as one or more large areas of contiguous non-zero block addresses. This might then leave the the DataCore LUN with SAUs that now only have all-zero data on them and that can then be reclaimed. However care should be taken that the act of defragmenting the data itself does not cause more SAU allocation as the block data is moved around (i.e. re-written to new areas on the DataCore LUN) during the re-organization. Page 20

21 Previous changes 2017 May Updated XenServer compatibility list XenServer 7.1 is now Qualified with SANsymphony-V 10.x with or without ALUA. April Added Known Issues QLogic QLA405x/406x iscsi HBAs Use QLogic s Firmware revision or greater This was previously documented in 'Known Issues - Third Party Hardware and Software' Updated XenServer compatibility list XenServer 7.1 has been added to the table and is currently considered 'not qualified' with SANsymphony 10.x Known Issues A hotfix is required for XenServer when using space TRIM/UNMAP commands on Virtual Disks that are larger than 2TB See: The URL to this hotfix has been corrected December Added Known Issues A hotfix is required for XenServer when using iscsi FE Ports Downloaded from here: November Updated Appendix C - Reclaiming storage SCSI UNMAP is now supported with SANsymphony-V 10.0 PSP 6 or greater Appendix C - Reclaiming storage Automatic and Manual reclamation These two sections have been re-written with more detailed explanations and technical notes. August Updated XenServer compatibility list Page 21

22 XenServer 7.0 is now supported with SANsymphony-V 10.x with or without ALUA. ALUA is now supported on XenServer 7.0 using Fibre Channel as well as iscsi front end connections. The XenServer Host Multipath Configuration Settings This has now been renamed to ' Multipath Configuration Settings for XenServer 6.x' Added The XenServer Host Multipath Configuration Settings for XenServer 7.x New settings are required when using XenServer 7.0 July Updated This document has been reviewed for SANsymphony 10.0 PSP 5. No updates were required. June Added XenServer compatibility list Added XenServer December 2015 This document combines all of DataCore s Citrix XenServer-related information from older Technical Bulletins into a single document including: Technical Bulletin 15c: "Citrix XenServer 5.6/6.x Hosts" Technical Bulletin 8: "Formatting Host s File Systems on Virtual Disks created from Disk Pools" Technical Bulletin 11: "Disk Timeout Settings on Hosts" Technical Bulletin 16: "Reclaiming Space in Disk Pools" Updated SANsymphony-V 8.x and all versions of SANsymphony 9.x before PSP4 Update 4 are now End of Life. Please see: End of Life Notifications and earlier Technical Bulletin 15c: "Citrix XenServer 5.6/6.x Hosts" January 2014 Updated the General known issue regarding discovering ISCSI IQNs using the wildcard option when using XenServer A hotfix from Citrix is now available.. December 2013 Added Citrix XenServer 6.2. Updated multipath.conf with a different prio setting for XenServer 6.2 when using iscsi and ALUA. Added a new General known issue regarding discovering ISCSI IQNs using the wildcard option when using XenServer August 2013 Removed all references for SANmelody as this product is now end of life. Updated Host Minimum Requirements section. Updated Host Supported Versions section. Completely updated the Known Issues section. Updated multipath.conf entries and notes (includes new configuration entries for Round Robin). Removed out-of-date Page 22

23 screenshots and instructions on how to configure XenServer using Citrix s own tools refer to Citrix s own documentation on how to configure and discover SRs and/or LUNs. October 2012 Updated the Configuring XenServer for Multipathing section. Added SANsymphony-V 9.x and removed the need for first 12 characters unique in vdisk names for SANsymphony-V Removed all (out of date) step-by-step instructions on how to manage and configure/format disk devices on the Host. November 2011 Added Citrix XenServer 6.x. removed all references to End of Life SANsymphony and SANmelody versions that are no longer supported as of July March 2011 Added SANsymphony-V R8.x December 2010 Initial Publication Page 23

24 COPYRIGHT Copyright 2017 by DataCore Software Corporation. All rights reserved. DataCore, the DataCore logo and SANsymphony are trademarks of DataCore Software Corporation. Other DataCore product or service names or logos referenced herein are trademarks of DataCore Software Corporation. All other products, services and company names mentioned herein may be trademarks of their respective owners. ALTHOUGH THE MATERIAL PRESENTED IN THIS DOCUMENT IS BELIEVED TO BE ACCURATE, IT IS PROVIDED AS IS AND USERS MUST TAKE ALL RESPONSIBILITY FOR THE USE OR APPLICATION OF THE PRODUCTS DESCRIBED AND THE INFORMATION CONTAINED IN THIS DOCUMENT. NEITHER DATACORE NOR ITS SUPPLIERS MAKE ANY EXPRESS OR IMPLIED REPRESENTATION, WARRANTY OR ENDORSEMENT REGARDING, AND SHALL HAVE NO LIABILITY FOR, THE USE OR APPLICATION OF ANY DATACORE OR THIRD PARTY PRODUCTS OR THE OTHER INFORMATION REFERRED TO IN THIS DOCUMENT. ALL SUCH WARRANTIES (INCLUDING ANY IMPLIED WARRANTIES OF MERCHANTABILITY, NON- INFRINGEMENT, FITNESS FOR A PARTICULAR PURPOSE AND AGAINST HIDDEN DEFECTS) AND LIABILITY ARE HEREBY DISCLAIMED TO THE FULLEST EXTENT PERMITTED BY LAW. No part of this document may be copied, reproduced, translated or reduced to any electronic medium or machine-readable form without the prior written consent of DataCore Software Corporation