On Thu, Aug 18, 2016 at 07:58:53PM +0200, Jose Luis Rodriguez Garcia wrote:
Hi, > As I understand LFS needs to do synchronous writes when there is > metadata operations (directories)/fsync operations involved. Instead > of writting a full segment (1 MB per default), it writes a "small > segment". It kills performance in RAID 5/6, because the write isn't a > full stripe: you have to read all the disks, for calculate the new > parity 1 write on raid of x disks= x reads + 2 writes (data + parity). > > The NVRAM memory solves this problem as buffer/ write cache. Sounds like WAFL https://en.wikipedia.org/wiki/Write_Anywhere_File_Layout Even though that article doesn't mention NVRAM, all Netapp filers have a (fixed) amount of NVRAM. Our big FAS8080 has 16384 MB NVRAM, the small FAS2554 has 2 GB NVRAM. Writes are very fast. Grtnx, -- B*E*R*T
