This configuration introduces some interesting challenges. The data from a stripe stored on one disk is called a chunk. If one disk fails, data on the failed disk can be rebuilt from the distributed data and parity on other disks. RAID 5 is a RAID configuration that uses disk striping with a distributed parity. RAID 5 overviewīecause RAID 5 and 6 are very similar, we’ll refer to these systems collectively as “RAID 5” to cover the challenges associated with both. Using a write-ahead log can address some of these issues and improve reliability of the array. However, software RAID - particularly software RAID 5 and 6 - also has some drawbacks, which can be problematic at Facebook’s scale. One workaround is to replace hardware RAID with software RAID. For example, if there is a failure in the array, it may not be immediately apparent which hard disk drive has the issue even when a failed disk is identified, physical access to the server might be required to fix it. Another minus is the lack of the ability to make any changes to hardware RAID.Hardware RAID often comes with transparency, management, and support challenges. In addition, even a good controller has a lifespan and will have to be replaced sooner or later. Also, a program array without severe performance loss can only use simple configurations and is subordinate to a specific operating system.ĭisadvantages of HW RAID: This RAID option will hit your wallet hard, since a good and proven controller does not come cheap. It is not possible to quickly replace a damaged disk, because first you have to turn off the system, and this is not always appropriate or convenient. Software RAID does not work with disk partitions. This also applies to reading and writing procedures. Software RAID vs Hardware RAID: Disadvantagesĭisadvantages of SW RAID: if you compare the performance of hardware vs software RAID, the software array is much weaker and slower. In addition, hardware arrays have a lot of additional functions and options. This array is more universal, as it can be used with various operating systems and can be recognized by any system. Also, there is no downtime when restoring a disk. SW RAID is considered safe, because it uses only the processing power of the operating system.Īdvantages of HW RAID: since the controller is used in this case, there is no load on the server motherboard and the write and read procedures are performed at high speed. The program array makes it possible to reconfigure the array easily and without any limits due to the controller. Software RAID vs Hardware RAID: AdvantagesĪdvantages of SW RAID: this array option is easy to install, because no additional hardware is needed. In addition, there are many advanced functions for user convenience and system protection for example, hot-swappable drives when a single drive fails. In this case, there is no additional load on the server processor and performance becomes noticeably higher. Hardware RAID (HW RAID) is an array with a discrete controller (ATA RAID, SATA controller, Delta PLC, etc.). In this case, the performance of such arrays is not great. Software RAID can support SCSI, SAS and SATA. Usually, SW RAID is connected to the system’s motherboard since all the data processing takes place on the server’s motherboard, the computation and execution time of the tasks on the device increases. Host controller resources are used here as a controller. Software RAID (SW RAID) is an array without a dedicated controller.
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