Whether the LUN can be read and written (whether the LUN can be used during initialization)


During LUN formatting, the LUN can be mapped to the host for reads and writes.

Other related questions:
Whether the IP address can be changed during LUN formatting
During LUN formatting, you can change the IP address of the management or service interface.

Whether the UUID of a LUN can be deleted
Can the UUID of a LUN be deleted? No. A UUID is a unique identifier of a LUN. Deleting the UUID will cause a drive letter shift.

Method used to plan LUN read/write policies
You can plan LUN read/write policies as follows: 1. Planning the write policy You can select the following write policies during LUN creation: write through, write back and mirroring, and write back without mirroring, mandatory write back and mirroring, and mandatory write back without mirroring. The following is the differences among write policies: Write through: writes data to disks. Each write operation must access the disk, contributing to low performance but high reliability. Write back: writes data to the cache and then write data to disks when there are idle host I/Os. Each write operation does not access the disk with high performance but low reliability. Write back and mirroring: writes data to both the local cache and peer cache simultaneously. Write back without mirroring: writes data to the local cache. Mandatory write back and mirroring: Storage devices must write data to the local cache and peer cache simultaneously. Mandatory write back without mirroring: Storage device must write data to the local cache. 2. Planning prefetch policies You can select the following prefetch polices: intelligent prefetch, constant prefetch, variable prefetch, and non-prefetch.

Method used to locate LUNs with poor read and write performance
Method used to locate LUNs with poor read and write performance: 1. The LUN write policy is write through. Locate the cause why the LUN write policy is write through. 2. If the host interface is iSCSI, check whether the network rate is 1 Gbit/s, whether the network is stable, and whether ping packets are lost. If the Fibre Channel or SAS network is used, log in to the storage's OSM page to check whether an alarm indicating that the front end encounters continuous error codes is reported. 3. Check whether slow disks exist in RAID groups. Specifically, run iostat -x 1 to check whether some disks differ from other disks (the util value of one or two disks is greater than that of other disks and reaches 100. If the util value of all disks in the RAID group reaches about 100, the configurations are incorrect and back-end disks are slow disks). If slow disks exist, replace them. 4. If a file system exists on the host, the file system produces enormous fragments when the disk space utilization rate exceeds 90%, causing the deterioration of read/write performance. You are advised to use disk space correctly.

LUN requirements for deduplication
When a thick LUN is created, the relationship between its physical and logical addresses has already been fixed. This does not meet deduplication requirements. For deduplication, you must modify the mapping relationship between the physical and logical addresses. In addition, deduplication requires space reclamation. The pointer of the thick LUN's logical address cannot be changed. Therefore, the space cannot be reclaimed.

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