Date: Tue, 2 Nov 2010 20:05:15 -0700 From: Jeremy Chadwick <freebsd@jdc.parodius.com> To: "Mikhail T." <mi+thun@aldan.algebra.com> Cc: fs@freebsd.org Subject: Re: Using an SSD "disk" for / Message-ID: <20101103030515.GA61758@icarus.home.lan> In-Reply-To: <4CD04AEC.8040607@aldan.algebra.com> References: <4CD04AEC.8040607@aldan.algebra.com>
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On Tue, Nov 02, 2010 at 01:31:24PM -0400, Mikhail T. wrote: > I'm setting up a new system and would like to use a moderate (64Gb > or 128Gb) SSD-drive to boot from. > > This will house /, /var, /home, and the /usr/local and thus see > plenty of activity, whenever src and ports are updated, or "world" > is remade, or packages are upgraded. I'm hoping, these operations > would be much faster, than with a regular HDD. > > However, people mention, that SSDs develop /severe/ performance > degradation if written to A LOT -- unless some SDD-specific > operation (TRIM) is used, but not all Operating Systems support > that... Does FreeBSD-8? Is that sufficient, or will an SSD degrade > quickly anyway? > > Does anyone use an SSD under FreeBSD? Which brand/model? Are you > happy with it? > > Also, what parameters should I give to newfs? SSDs' characteristics > seem rather different from HDDs', so it is unlikely, that newfs' > defaults will be optimal for an SSD... Would a different filesystem > (ZFS?) be a better choice, than FFS, for these devices? Yes, I use SSDs as the OS disk. Depending on the system's needs, I use one of the following models: - Intel X25-V 40GB - Intel X25-M 80GB The reason I go with Intel disks is because they dominate all other SSD brands when it comes to IOPS. I'm less interested in sequential throughput in this particular case. I also go with Intel because I have a pretty severe dislike for OCZ products (and that's my problem/issue not yours). I use UFS2 + softupdates on all filesystems on the SSDs (except for the root filesystem, which lacks SU). Those filesystems are /, swap, /usr, /tmp, and /var. I do not do any "tuning" of the filesystems either, so I imagine there's room for speed improvements there as well. As for the performance: it's something you'll have to see for yourself. The performance is outright amazing when it comes to administrative tasks (OS installation, newfs, massive copies of data to/from the SSD, updating /usr/src and /usr/ports, etc.). Try a build/install world or kernel sometime on an SSD and watch your terminal. You'll be pretty impressed. Our systems which use SSDs *always* have at least one mechanical HDD included in the system (in fact usually 3, using ZFS raidz1). These are used for things like /var/mail and /home. As for TRIM and the like -- yes, that's a concern of mine as well, but for right now I just monitor the SSDs with smartmontools 5.40 and smartctl -a. If I had to make a recommendation of which drive to get, I would say get a drive that offers at least 80GB. I have to make some sacrifices with the 40GB. Having swap and /var (thus /var/crash) that's big enough to handle a kernel panic is important to me, so effectively the more RAM's in the machine the bigger the SSD needs to be. 80GB seems to be okay for our setups. -- | Jeremy Chadwick jdc@parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, USA | | Making life hard for others since 1977. PGP: 4BD6C0CB |
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