Re: [gentoo-user] Re: [Gentoo-User] emerge --sync likely to kill SSD?

[microcai]

2014-06-21 1:48 GMT+08:00 Kai Krakow <hurikhan77@×××××.com>:
> microcai <microcai@×××××××××××××.org> schrieb:
>
>> rsync is doing bunch of  4k ramdon IO when updateing portage tree,
>> that will kill SSDs with much higher Write Amplification Factror.
>>
>>
>> I have a 2year old SSDs that have reported Write Amplification Factor
>> of 26. I think the only reason is that I put portage tree on this SSD
>> to speed it up.
>
> Use a file system that turns random writes into sequential writes, like the
> pretty newcomer f2fs. You could try using it for your rootfs but currently I
> suggest just creating a separate partition for it and either mount it as
> /usr/portage or symlink that dir into this directory (that way you could use
> it for other purposes, too, that generate random short writes, like log
> files).
>
> Then, I'd recommend changing your scheduler to deadline, bump up the io
> queue depth to a much higher value (echo -n 2048 >
> /sys/block/sdX/queue/nr_requests) and then change the dirty io flusher to
> not run as early as it usually would (change vm.dirty_writeback_centisecs to
> 1500 and vm.dirty_expire_centisecs to 3000). That way the vfs layer has a
> chance to better coalesce multi-block writes into one batch write, and f2fs
> will take care of doing it in sequential order.
>
> I'd also suggest not to use the discard mount options and instead create a
> cronjob that runs fstrim on the SSD devices. But YMMV.
>
> As a safety measure, only ever partition and use only 70-80% of your SSD so
> it can reliably do its wear-leveling. It will improve lifetime and keep the
> performance up even with filled filesystems.
>
> --


many thanks to all of you!

no I've put my portage tree on an F2FS partation now.