Important Notice: Our web hosting provider recently started charging us for additional visits, which was unexpected. In response, we're seeking donations. Depending on the situation, we may explore different monetization options for our Community and Expert Contributors. It's crucial to provide more returns for their expertise and offer more Expert Validated Answers or AI Validated Answers. Learn more about our hosting issue here.

Where does DiskSuite store the RAID5 “log” and how large is it?

April 26, 2017Disksuite large log raid5 store

0

Posted

Where does DiskSuite store the RAID5 “log” and how large is it?

1 Answer

0

Posted

There is no RAID5 log. Instead, DiskSuite uses a prewrite area. If you view metastat output from a RAID5 device, you will see that the start block for each column in the RAID is greater than zero. This is because DiskSuite allocated the first part of each column to the prewrite area. When a write occurs on a RAID5 device, the data and parity are first written to the prewrite areas of the appropriate columns. Next, iodone is called for the operation so that the writing process can continue. The data is then written to the active area of the RAID device. When that operation is done, the temporary copy in the prewrite area is freed up. If the system crashes, DiskSuite rolls the completed prewrite transactions to the active area. Thus, the integrity of the RAID device is protected against crashes.