联想SureSAS 112新创建的卷无法正常读写处理

背景：在测试的联想SureSAS 112上进行控制器固件升级和降级测试，期间出现故障，无法升级成功。在物理重启存储后，两个控制器之间可能没有进行正常同步，导致一个卷故障，无法正常读写。由于该卷为测试卷，没有生产数据，因此手工进行了删除。

然而，后来将新创建的卷映射给主机后，主机也还是无法读写。从存储上看，卷的状态是正常的：
但是在“system event”中，出现了告警信息 “Controller A WARNING Unwritable write-back cache data exists for a volume. (vdisk: unknown name, volume: unknown name, SN: 00c0ff1b2c40000050e5a35301000000) It comprises 98% of cache space. ”，如下所示：

可能是微码升级和物理重启存储时导致之前已经删除的故障卷的cache数据无法正常写入磁盘，导致之前的故障卷出故障。而新建的卷的名称和删除前相同，同时cache也被数据占用了98%的空间，导致新创建的卷也不能正常读写。

查看存储的help命令帮助，列表中包含以下命令：
clear cache - Clears unwritable cache data from both controllers

于是使用命令clear cache清除了存储中残留的无效cache数据，卷立即恢复了，可以正常读写。

注意：这个命令只能在卷没有数据时执行，否则清除cache数据会导致卷数据丢失，产生严重后果。

附录：SureSAS 112命令列表

# help
abort replication - Aborts the current replication operation on the specified secondary volume
abort scrub - Aborts a scrub operation for specified vdisks or disks
abort verify - Aborts the verify vdisk operation for specified vdisks
abort volumecopy - Aborts copying a volume
add replication-volume - Adds an existing secondary volume to a replication set
clear cache - Clears unwritable cache data from both controllers
clear disk-metadata - Clears metadata from leftover disks
clear events - For use by or with direction from a service technician
clear expander-status - For use by or with direction from a service technician
convert master-to-std - Converts a specified master volume into a standard volume; that is, it disables the volume from accepting snapshots
convert std-to-master - Converts a standard volume to a master volume; that is, it enables the volume for snapshots and associates it with an existing snap pool
create certificate - Creates or removes a custom security certificate
create chap-record - For iSCSI, creates a CHAP record to authenticate login requests
create host-wwn-name - Deprecated; use "create host"
create host - Creates a host entry with an associated nickname
create master-volume - Creates a volume that is enabled for snapshots
create remote-system - Creates a persistent association with a remote storage system
create replication-set - Creates a replication set from a specified standard or master volume
create schedule - Schedules a task to run automatically
create snap-pool - Creates a snap pool to use for snapshot data
create snapshots - Creates a snapshot of each specified source volume
create task - Creates a task that can be scheduled
create user - Creates a user account
create vdisk - Creates a vdisk using the specified RAID level, disks, and spares
create volume-set - Creates a specified number of volumes in a vdisk
create volume - Creates a volume in a vdisk
delete all-master-volumes - Deletes all master volumes associated with a specified snap pool
delete all-snapshots - Deletes all snapshots associated with a specified volume
delete chap-records - For iSCSI, deletes a specified CHAP record or all CHAP records
delete global-spare - Deletes specified global spare disks
delete host-wwn-name - Deprecated; use "delete host"
delete host - Deletes a discovered or manually created host
delete iscsi-host - Deprecated; use "delete host"
delete master-volume - Deletes a master volume
delete remote-system - Deletes the persistent association with a remote system
delete replication-set - Dissolves a replication set
delete schedule - Deletes a task schedule
delete snap-pool - Deletes a snap pool
delete snapshot-write-data - Deletes data written to a standard snapshot after it was created
delete snapshot - Deletes specified snapshots
delete task - Deletes a task
delete user - Deletes a user account
delete vdisk-spare - Deletes specified spares that are assigned to a vdisk
delete vdisks - Deletes specified vdisks
delete volumes - Deletes specified volumes
dequarantine - Removes a vdisk from quarantine
detach replication-volume - Prepares a secondary volume to be physically removed from a system
expand snap-pool - Expands a snap pool
expand vdisk - Adds disks to a vdisk 
expand volume - Expands a standard volume
export snapshot - Exports a replication snapshot on the local system to a new standard snapshot
help - Provides tips for viewing help and using command shortcuts
map volume - Maps specified volumes using settings that override the volumes' default mapping
meta - In XML API format only, shows all property metadata for objects
ping - Tests communication with a remote host
reattach replication-volume - Reattaches a secondary volume to its replication set
release volume - Clears host registrations and releases persistent reservations for all or specified volumes
remote - Runs a command on a remote system that is associated with the local system
remove replication-volume - Removes a secondary volume from a replication set
replicate snapshot - Initiates a replication operation using an existing snapshot as the data source
replicate volume - Creates a replication snapshot of the specified volume and initiates a replication operation
rescan - This command forces rediscovery of disks and enclosures in the storage system
reset all-statistics - Resets performance statistics for both controllers
reset controller-statistics - Resets performance statistics for controllers
reset disk-error-statistics - Resets error statistics for all or specified disks
reset disk-statistics - Resets performance statistics for disks
reset host-channel-link - Deprecated; use "reset host-link"
reset host-link - Resets specified controller host ports (channels)
reset host-port-statistics - Resets performance statistics for controller host ports
reset smis-configuration - Resets the SMI-S configuration files
reset snapshot - Deletes the data in a standard snapshot and resets it to the current data in the associated master volume
reset vdisk-statistics - Resets performance statistics for all or specified vdisks
reset volume-statistics - Resets performance statistics for all or specified volumes
restart - Restarts the Storage Controller or Management Controller in a controller module
restore defaults - For use by or with direction from a service technician
resume replication - Resumes a suspended replication operation on the specified secondary volume
rollback master-volume - Rolls back (reverts) the data on a master volume to the data that exists in a specified snapshot
scrub disks - Analyzes specified disks to find and fix disk errors
scrub vdisk - Analyzes specified vdisks to find and fix disk errors
set advanced-settings - Sets advanced system configuration options
set auto-write-through-trigger - Sets the trigger conditions that cause the controller to change the cache policy from write-back to write-through
set awt - See help for "set auto-write-through-trigger"
set cache-parameters - Sets a volume's cache options
set chap-record - For iSCSI, changes an originator's CHAP record
set cli-parameters - Sets options that control CLI behavior
set controller-date - Sets date and time parameters for the system
set debug-log-parameters - For use by or with direction from a service technician
set disk-parameters - Sets parameters that affect disk operation
set drive-parameters - Deprecated; use "set disk-parameters"
set email-parameters - Sets SMTP notification parameters for events and managed logs
set enclosure - Sets an enclosure's name, location, rack number, and rack position
set expander-fault-isolation - For use by or with direction from a service technician
set expander-phy - For use by or with direction from a service technician
set global-spare - Deprecated; use "set spares"
set host-name - Changes the nickname of a host entry
set host-parameters - Sets controller host-port parameters for communication with attached hosts
set host-wwn-name - Deprecated; use "set host-name"
set iscsi-host - Deprecated; use "set host-name"
set iscsi-parameters - For iSCSI, changes system-wide iSCSI parameters
set job-parameters - Sets parameters for background vdisk scrub, partner firmware upgrade, and other jobs
set led - Changes the state of the identification LED on a specified disk or enclosure
set network-parameters - Sets parameters for controller module network ports
set ntp-parameters - Sets Network Time Protocol (NTP) parameters for the system
set output-format - Deprecated; use "set cli-parameters"
set password - Sets a user's password for system interfaces (such as the CLI)
set priorities - Sets snapshot-retention priorities for a specified snap pool
set prompt - Sets the prompt for the current CLI session
set protocols - Enables or disables management services and protocols
set remote-system - Changes remote-system credentials stored on the local system
set replication-primary-volume - Changes the primary volume for a replication set
set replication-volume-parameters - Sets parameters for a specified replication volume
set schedule - Changes parameters for a specified schedule
set snap-pool-policy - Sets the recovery policy that determines the action taken when a specified snap pool's error and critical threshold levels are reached
set snap-pool-threshold - Sets the percentages of snap-pool space used that trigger the warning and error threshold policies
set snmp-parameters - Sets SNMP parameters for event notification
set spares - Creates or deletes spare disks for redundant (RAID 1, 3, 5, 6, 10, 50) vdisks
set system - Sets the system's name, contact, location, and description
set task - Changes parameters for a TakeSnapshot, ReplicateVolume, or VolumeCopy task
set user - Changes user preferences for the session or permanently
set vdisk-spare - Deprecated; use "set spares"
set vdisk - Changes parameters for a specified vdisk
set volume - Changes a volume's name and identifying information
show advanced-settings - Shows the settings for advanced system-configuration options
show auto-write-through-trigger - Shows the system's write-through trigger settings
show awt - See help for "show auto-write-through-trigger"
show cache-parameters - Shows cache settings and status for the system and optionally for a volume
show certificate - Shows the status of the system's security certificate
show channels - Deprecated; use "show ports"
show chap-records - For iSCSI, shows all CHAP records or the record for a specific originator
show cli-parameters - Shows the current CLI session preferences
show configuration - Shows system configuration information
show controller-date - Shows the system's current date and time
show controller-statistics - Shows live performance statistics for controller A, B, or both
show controllers - Shows information about each controller module in the storage system
show debug-log-parameters - For use by or with direction from a service technician
show disk-parameters - Shows disk settings
show disk-statistics - Shows live or historical performance statistics for disks
show disks - Shows information about disks in the storage system
show drive-parameters - Deprecated; use "show disk-parameters"
show email-parameters - Shows email (SMTP) notification settings for events and managed logs
show enclosure-status - Deprecated; use "show enclosures", "show frus", or "show sensor-status"
show enclosures - Shows information about the enclosures in the storage system
show events - Shows events logged by each controller in the storage system
show expander-status - For use by or with direction from a service technician
show fans - Shows information about each fan in the storage system
show frus - Shows FRU (field-replaceable unit) information for the storage system
show host-maps - Shows mapping information for volumes that are mapped to all hosts or to a specified host
show host-parameters - Shows information about host ports on both controllers
show host-port-statistics - Shows live performance statistics for each controller host port
show host-wwn-names - Deprecated; use "show hosts"
show hosts - Shows hosts that volumes can be mapped to
show inquiry - Shows inquiry data for each controller module
show iscsi-parameters - For iSCSI, shows system-wide iSCSI parameters
show job-parameters - Shows parameters for background vdisk scrub, partner firmware upgrade, and other jobs
show license - Shows the status of licensed features in the storage system
show lun-maps - Deprecated; use "show volume-maps"
show master-volumes - Shows information about all master volumes, or ones associated with a specified controller or snap pool
show network-parameters - Shows the settings and health of each controller module's network port
show ntp-status - Shows the status of the use of Network Time Protocol (NTP) in the system
show output-format - Deprecated; use "show cli-parameters"
show port-wwn - Deprecated; use "show ports"
show ports - Shows information about host ports on both controllers
show power-supplies - Shows information about each power supply in the storage system
show priorities - Shows snapshot-retention priorities for a specified snap pool
show protocols - Shows which management services and protocols are enabled or disabled
show redundancy-mode - Shows the redundancy status of the system
show refresh-counters - In XML API format only, shows when the data represented by the basetype was last updated
show remote-systems - Shows information about remote systems associated with the local system
show replication-images - Shows information about replication images for a specified replication volume
show replication-sets - Shows information about replication sets on the local system
show replication-volumes - Shows information about volumes in replication sets
show sas-link-health - Shows the condition of SAS expansion-port connections
show schedule-details - Shows information about a specified task schedule
show schedules - Shows information about all task schedules
show sensor-status - Shows the status of each environmental sensor in each enclosure
show shutdown-status - Shows whether each Storage Controller is active or shut down
show snap-pools - Shows information about snap pools owned by a specified controller or both controllers
show snapshots - Shows information about snapshots for a specified controller, master volume, or snap pool
show snmp-parameters - Shows SNMP settings for event notification
show system-parameters - Shows the current settings for the storage system
show system - Shows information about the system
show task-details - Shows information about a specified task
show tasks - Shows information about all tasks
show unwritable-cache - Shows the percentage of unwritable cache data in the system
show users - Shows configured user accounts
show vdisk-statistics - Shows live or historical performance statistics for vdisks
show vdisks - Shows information for all or specified vdisks
show versions - See help for "versions"
show volume-maps - Shows mapping information for a specified volume or for all volumes
show volume-names - Shows volume names and serial numbers
show volume-reservations - Shows persistent reservations for all or specified volumes
show volume-statistics - Shows live performance statistics for all or specified volumes
show volumecopy-status - Shows information about in-progress volume copy operations
show volumes - Shows volume information for all or specified vdisks
shutdown - Shuts down the Storage Controller in a controller module
start vdisk - Restarts a vdisk that was stopped in order to move its disks into this system
stop vdisk - Stops a vdisk to prepare its disks for removal
suspend replication - Suspends the current replication operation on the specified secondary volume
test - Sends a test message to configured destinations for event notification and managed logs
trust - Enables an offline vdisk to be brought online for emergency data recovery
unmap volume - Deletes explicit mappings or the default mapping for specified volumes
verify links - Verifies host-port links
verify remote-link - Verifies host-port links between the local system and a specified remote system
verify vdisk - Analyzes redundant vdisks to find and fix inconsistencies between their redundancy data and their user data
versions - Shows firmware and hardware version information for each controller module
volumecopy - Copies a standard, master, or snapshot volume to a new standard volume