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albright
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Joined: 16 Nov 2003
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PostPosted: Mon Nov 03, 2014 2:37 pm    Post subject: question about os x and trim Reply with quote

totally unrelated to gentoo, except the knowledge level here
is very high

I installed a samsung ssd into an old imac (cirac 2008); all
is good (like getting a new computer)

as you may know, trim is disabled for non-apple approved ssds
and can only be enabled by turning off kext security feature, which
can lead to trouble in various ways

so, my question is this:

is it possible/safe to just boot system rescue on the imac every so often
and run fstrim? (this is of course an HFS+ files system)

maybe this is a dumb question; please let me know either way
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katfish
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Joined: 14 Nov 2011
Posts: 147

PostPosted: Mon Nov 03, 2014 10:47 pm    Post subject: Reply with quote

Trim is a continuous process. Whenever the FS frees blocks, it reports them to the SSD which does its job then.
So if there is no "instance" in the OS that is reporting, the SSD becomes no information about what is in use or not.

You only can repartition the drive from time to time in order to start the trim process if OS doesn't (IMHO).
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katfish
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PostPosted: Tue Nov 04, 2014 3:31 pm    Post subject: Reply with quote

Today, I recompiled the kernel of one of my machines and saw that linux has HFS+ support.

Quote:
CONFIG_HFSPLUS_FS:

If you say Y here, you will be able to mount extended format
Macintosh-formatted hard drive partitions with full read-write access.

This file system is often called HFS+ and was introduced with
MacOS 8. It includes all Mac specific filesystem data such as
data forks and creator codes, but it also has several UNIX
style features such as file ownership and permissions.


I don't know if trim is also supported and I have no deeper OSX knowledge,
but if you can boot a linux live system which has hfs+ support compiled in, you can test that.

www.sysresccd.org should have support for all common file systems.

and don't forget to backup your data before you make changes to your file system ;)
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Ant P.
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Joined: 18 Apr 2009
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PostPosted: Tue Nov 04, 2014 11:15 pm    Post subject: Reply with quote

Does fstrim need the underlying filesystem to support it? Because neither of Linux's HFS variants do. Try it, but be warned it may just do nothing at all.
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djdunn
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Joined: 26 Dec 2004
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PostPosted: Thu Nov 06, 2014 7:11 am    Post subject: Reply with quote

android uses fstrim on ext4, so I gather it wouldn't be impossible.
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Atha
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Joined: 22 Sep 2004
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PostPosted: Mon Oct 05, 2015 9:11 pm    Post subject: Reply with quote

This is what you were looking for:
  • https://wiki.archlinux.org/index.php/Solid_State_Drives#TRIM
  • https://wiki.debian.org/SSDOptimization

From the first we find that currenctly, as of Kernel 3.8, only Ext4, Btrfs, JFS, VFAT, XFS, F2FS support TRIM. Also the ntfs-3g FUSE driver supports TRIM as of version 2015.3.14. All of them can use the discard mount option and all of them, except VFAT, can use the fstrim utility.

Unfortunately HFS+ is not supported.
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