jj999c

同Fragment無關係，只係修改Data會影響數條軌，正常CMR改一個sector做係改一個，SMR修改一個舊sector做 ...
hoho1986 發表於 2020-9-25 09:59

    got it
thanks

harryytm

will buy,  thanks
jj999c 發表於 2020-9-24 17:28

MD04ACA400我有一隻用過唔錯

totalz

同Fragment無關係，只係修改Data會影響數條軌，正常CMR改一個sector做係改一個，SMR修改一個舊sector做 ...
hoho1986 發表於 2020-9-25 09:59

Problem is it requires uses of free space to temporary store the update, and do the real update in idle time.  So It could cause a lot of fragmentations when free space is running out...

via HKEPC IR Pro 3.6.1 - Android(3.3.1)

harryytm

got it
thanks
jj999c 發表於 2020-9-25 11:04

補充一下
其實 SMR 硬碟已經用類似 SSD 嘅管理方式
磁區地址(即係 LBA)並唔係固定而係動態由 Firmware 管理
啲數據實際上寫喺碟片邊個位由 Firmware 決定

SMR 硬碟將碟片分成 PMR 區同 SMR 區
碟片外圈係 PMR 而內圈係 SMR
個 Firmware 會將連續寫入會自動分流去 SMR 區
而細嘅寫入會分流咗去 PMR 區

SMR 硬碟嘅 Firmware 會自已記錄邊啲 SMR 位未用
可以唔需要重新叠磁軌直接寫入
新嘅 SMR 硬碟會透過 TRIM 去回收未用空間
進一步減少需要重新叠磁軌嘅機會

harryytm

Problem is it requires uses of free space to temporarily store the update, and do the real update in ...
totalz 發表於 2020-9-25 12:26

You must get the concept right about SMR disks.

The LBA to sector mapping of an SMR HDD is dynamically managed by firmware just like an SSD, which the sector LBA is emulated by the firmware on the fly and transparent to the OS, the firmware can fool the OS a file is unfragmented, but in fact, it is heavily fragmented internally on the platter.

On the contrary, on a "Normal" PMR or CMR HDD, the LBA to sector mapping is static unless there is a bad sector that the firmware has to remap it to a spare sector.

gunsix

You must get the concept right about SMR disks.

The LBA to sector mapping of an SMR HDD is dynamic ...
harryytm 發表於 2020-9-25 12:48 PM

如果以長命計 (係咪叫 MTTF?), SMR 有冇好處? Thx

harryytm

如果以長命計 (係咪叫 MTTF?), SMR 有冇好處? Thx
gunsix 發表於 2020-9-26 10:27

無好處