Date: Mon, 16 Nov 1998 17:07:31 -0500 (EST) From: Chuck Robey <chuckr@mat.net> To: Brian Handy <handy@lambic.physics.montana.edu> Cc: hackers@FreeBSD.ORG Subject: Re: CCD question Message-ID: <Pine.BSF.4.05.9811161702230.6431-100000@picnic.mat.net> In-Reply-To: <Pine.BSF.4.05.9811161448490.774-100000@lambic.physics.montana.edu>
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On Mon, 16 Nov 1998, Brian Handy wrote:
> Hey folks,
>
> Here's something I'm wondering how people handle -- I have a couple of
> 18GB disks I'm striping together, mostly for the convenience of having one
> largish contiguous playground to work in. But I'm sorely disappointed at
> the space I end up with -- Two big drives, with the default 8% reserved
> free space, ends up being a lot. What I end up with for these two ccd'd
> drives is this:
>
> %df /mnt
> Filesystem 1K-blocks Used Avail Capacity Mounted on
> /dev/ccd0c 34506495 1 31745975 0% /mnt
>
> That's a lot of space to lose. I'm the sole user of this ccd, and it's
> just for data and figures and paper-writing activities and data analysis
> stuff -- any suggestions on how I should set this up to take advantage of
> as much space as possible, without causing myself problems down the road?
> I've seen various threads discussing this, but I don't think I understand
> the issues well enough to make a very informed decision.
Interesting. It's controlled by search time for free blocks, I think.
You're only losing 8% still, it's just 8% of a whopping big disk. I
assume the value 34506495 represents the useable disk space after
formatting (something about 17.2G per disk, right?). The rest of the
math then works out. How much does something like that cost, nowadays?
Tunefs says:
-m minfree
Specify the percentage of space held back from normal users; the
minimum free space threshold. The default value used is 8%.
This value can be set to zero, however up to a factor of three in
throughput will be lost over the performance obtained at a 10%
threshold. Settings of 5% and less force space optimization to
always be used which will greatly increase the overhead for file
writes. Note that if the value is raised above the current usage
level, users will be unable to allocate files until enough files
have been deleted to get under the higher threshold.
(here's hoping your mailer doesn't crunch that). Personally, I think
I'd stay with what you've got, unless your fs has some specific goal in
mind .... if it was mostly read-only, then I'd cut the minfree quite a
bit.
----------------------------+-----------------------------------------------
Chuck Robey | Interests include any kind of voice or data
chuckr@glue.umd.edu | communications topic, C programming, and Unix.
213 Lakeside Drive Apt T-1 |
Greenbelt, MD 20770 | I run Journey2 and picnic (FreeBSD-current)
(301) 220-2114 | and jaunt (NetBSD).
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