Dell PowerEdge R760 PowerEdge RAID Controller S160 Users Guide - Page 14
Virtual Disks, Virtual disk features, TRIM for SATA SSDs
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3 Virtual Disks A logical grouping of physical disks attached to a PERC S160 allows you to create multiple virtual disks of the same RAID levels, without exceeding a maximum of 30 virtual disks. The PERC S160 controller allows: ● Creating virtual disks of different RAID levels on a S160 controller. NOTE: Ensure that you do not mix RAID levels on the same physical disks. ● Building different virtual disks with different characteristics for different applications. ● Creating virtual disks from a mix of NVMe PCIe SSD 2.5-inch SFFs and NVMe PCIe SSD adapters. The PERC S160 controller does not allow: ● Creating a virtual disk from a mix of different types of physical disks. For example, a RAID 10 virtual disk cannot be created from two SATA HDD physical disks and a SATA SSD physical disk. All the physical disks must be of the same drive type (HDD/SSD/NVMe PCIe SSDs). ● Selecting a physical disk as a dedicated hot spare if the physical disk is a different type from the physical disk of the virtual disks. A virtual disk refers to data storage which a controller creates using one or more physical disks. NOTE: A virtual disk can be created from several physical disks; the operating system considers it a single disk. The capacity of a virtual disk can be expanded online for any RAID level without rebooting the operating system. NOTE: If the boot VD is spanned across different SATA controllers, then Windows Hardware Quality Labs testing (WHQL), DF - Reinstall with I/O Before and After (Reliability) fails in a server having two SATA controllers. Topics: • Virtual disk features • Disk initialization • Background Array Scan • Checkpointing • Virtual disk cache policies • Virtual disk migration • Expanding virtual disk capacity Virtual disk features TRIM for SATA SSDs The TRIM command allows an operating system to delete a block of data that is no longer considered in use from the SATA SSDs. TRIM resolves the Write Amplification issue for supported operating systems. When an operating system deletes a file, the file is marked for deletion in the file system, but the contents on the disk are not actually erased. As a result, the SSDs do not know that the Logical Block Addressing (LBA) file previously occupied can be erased. With the introduction of TRIM, when a file is deleted, the operating system sends a TRIM command along with the LBAs that do not contain valid data. NOTE: The TRIM feature is supported only on pass-through SSDs. NOTE: The TRIM feature is not supported on NVMe PCIe SSDs. 14 Virtual Disks