Re:FreeBSD and ZFS
by takeda on Saturday February 27, 2016 @01:44PM
(#11187959)
Few minor things.
ARC actually is optional, and in fact FreeBSD disables it by default if you have less than 2GB RAM.
1GB per TB or more like 5GB per TB is rule of thumb if you use deduplication. If you don't use deduplication it's more of: "the more RAM you have the better performance you get for reading"
ARC is not for writing. It's purely used for improving read performance. For improving write performance you use ZIL device. ZIL is essentially a journal. If you don't specify ZIL device ZFS will store it on data disks. If writing performance is important it is recommended to keep ZIL on separate device (especially SLC SSD). More about ZIL: http://nex7.blogspot.com/2013/04/zfs-intent-log.html
ARC actually is optional, and in fact FreeBSD disables it by default if you have less than 2GB RAM.
1GB per TB or more like 5GB per TB is rule of thumb if you use deduplication. If you don't use deduplication it's more of: "the more RAM you have the better performance you get for reading"
ARC is not for writing. It's purely used for improving read performance. For improving write performance you use ZIL device. ZIL is essentially a journal. If you don't specify ZIL device ZFS will store it on data disks. If writing performance is important it is recommended to keep ZIL on separate device (especially SLC SSD). More about ZIL: http://nex7.blogspot.com/2013/04/zfs-intent-log.html