(g) Code to make ext4 HA-SMR aware: 2015, Seagate, (f) DM-SMR and CMR zones, resilvering woes: (e) HM-SMR paper: 2013, Albert Chen et al, WD: (c) HA-SMR education: 2014, Mary Dunn and Tim Feldman of Seagate, (b) HA-SMR presentation, recording: 2014, Tim Feldman, (a) HA-SMR and HM-SMR in ZFS: 2014, Tim Feldman of Seagate, Precise models vary and are not guaranteed assume SMR in capacities below 8TB.Īll current Barracuda, Firecuda, Skyhawk Lite/Mini models List of SMR drives known to the community:Īll 2-6TB external drives - Elements, My Book, Easystore, etc. See page 24 of (d) as well as (i) and (j). I am assuming ZFS does not currently handle HA-ZFS or HM-ZFS drives, as this would require Block Pointer Rewrite. Host Managed, HM-SMR, which is not backwards compatible and requires ZFS to manage the SMR process. Without that code, a HA-SMR drive behaves like a DM-SMR drive where ZFS is concerned. Note that ZFS code to use HA-SMR does not appear to exist. Host Aware, HA-SMR, which is designed to give ZFS insight into the SMR process. As a rule of thumb, avoid DM-SMR drives, unless you have a specific use case where the increased resilver time (a week or longer) is acceptable, and you know the drive will function for ZFS during resilver. This means ZFS cannot "target" writes, and is the worst type for ZFS use. Drive Managed, DM-SMR, which is opaque to the OS. This thread attempts to pull together known SMR drives, and the sources for that information. It is often desirable to choose a CMR drive instead. SMR has worse sustained write performance than CMR, which can cause severe issues during resilver or other write-intensive operations, up to and including failure of that resilver. SMR is well suited for high-capacity, low-cost use where writes are few and reads are many. The first drives are expected in 2020, in either flavor. New technology such as HAMR (Heat Assisted Magnetic Recording, Seagate) or MAMR (Microwave Assisted Magnetic Recording, WD) can be used with or without shingling. SMR allows vendors to offer higher capacity without the need to fundamentally change the underlying recording technology. This table will use CMR (Conventional Magnetic Recording) to mean "PMR without the use of shingling". The tracks are perpendicular, they are also shingled - layered - on top of each other. SMR is a form of PMR (Perpendicular Magnetic Recording). For cost and capacity reasons, manufacturers are increasingly moving to SMR, Shingled Magnetic Recording. Hard drives that write data in overlapping, "shingled" tracks, have greater areal density than ones that do not.
0 kommentar(er)
