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I need to disable prealloc feature in ext4. But there is not a mount feature called disprealloc. I would like to know if there are any methods to disable prealloc feature.

Any suggestions in this regard will be appreciated

Nayantara Jeyaraj
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wenyi liu
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  • What do you mean by prealloc feature? discard/nodiscard seems to be what you are looking for. – itisravi Oct 18 '16 at 04:52
  • maybe not,discard/nodicard is feature associated with deleting file,most used in SSD write amplification.I have finished disable prealloc in ext4 code,It is not very difficult....I was scared before – wenyi liu Oct 19 '16 at 01:49
  • There is no such thing as "prealloc" feature in ext4. Can you say a bit more about what you think you are wanting to disable and why you want to disable it? – Theodore Ts'o Oct 24 '16 at 04:58
  • I have got a SMR/HA disk,but the random read/write is bad.So I want to change ext4 in linux-4.2.0 to fit in SMR/HA feature,and the ext4 of linux-4.2.0 is on basis of seagate smr_fs_ext4.I want to set write position in write pointer,so I want to disble prealloc feature and I really have done this.thanks a lot for your attention,now I think change ext4 to fit in SMR/HA disk is a lot of work and ext4 is not a smr/ha friendly filesystem, so I think maybe this is not very feasible. – wenyi liu Oct 25 '16 at 02:16

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