I just got notified my new Thinkpad X220 is on it's way, and I'm thinking
about the best way to use it. ;) Obviously, FreeBSD with ZFS is on top of
the list. (De-dup and compression on my space-limited laptop? Yes,
please.)
Some relevant vitals (after a couple of upgrades that are also on their
way):
6GB of RAM
250GB 2.5in HDD
40GB mSATA SSD
I'm planning on installing the patched version of 8.2, with the patches for
ZFS v28. My idea at this point is to use the main HDD as the primary
drive, with the SSD partitioned into a small[1] ZIL-device and a larger
cache drive. Since it's a SSD, I don't think disk contention should be an
issue for that use, and it should speed up both reads and writes. It might
even reduce the amount of main-disk use that happens. (Or at least, make
it happen in short bursts, and let the drive idle in between.)
I might still upgrade that HDD to something larger than stock. I could go
to an SSD there too (and it's on a SATA III connection, so it could be a
*faster* SSD), but I think I'm more likely to go with more space if I
decide to upgrade.
Obviously, I'm not afraid of a weird config in this case. ;) I'm also not
trying to optimize hard for space, or for any specific use-case: I tend to
use a laptop for light-duty when I'm not traveling, then more heavy-duty
(as well as watching movies, etc) during occasional traveling. The idea
here is to let ZFS do the disk optimization. It'll probably slow down my
boot times from what could be possible, but I'm hoping ZFS will do things
like move a movie I'm *currently* watching to the cache drive, and let the
machine shut down the hard drive.
Two things I'm *not* sure what the best choices for are the swap partition,
and the boot sector. Swap could be on the HDD (slow, reduces my apparent
disk-space), on the SSD (fast, reduces my most valuable disk space), or in
ZFS (doesn't use dedicated space, but has stability issues under heavy
load). Of course I may not ever *need* much swap, as I have a fair amount
of RAM. (And I don't care about crash dumps on this box.)
The boot sector doesn't really matter as much; if I go with a dedicated
swap partition that will probably also hold the boot sector. Otherwise,
I'm leaning towards the SSD, as I'm already planning on partitioning that,
and I'm less likely to pull it out.
Or, of course, there may be other considerations that I've overlooked in
the rest. So, I'm looking for wisdom, or other thoughts people have. ;)
Daniel T. Staal
[1] As per:
<http://www.solarisinternals.com/wiki/index.php/ZFS_Best_Practices_Guide#Separate_Log_Devices>
ZIL devices will never use more than 1/2 of RAM, at absolute max, and in
most cases will use significantly less. Fully upgraded, this machine
supports 8GB of RAM, so a 4GB ZIL device would be plenty in all cases, and
would probably be overkill.
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