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Date:      Thu, 5 May 2011 09:40:32 +0100
From:      krad <kraduk@gmail.com>
To:        FreeBSD Questions <freebsd-questions@freebsd.org>
Subject:   Re: Laptop Multi-HD partitioning advice (ZFS)
Message-ID:  <BANLkTi=gfsBk+byV=8KgfrsJbXdWk8VrcA@mail.gmail.com>
In-Reply-To: <267B4CEEF5135C2FE0F2087E@mac-pro.magehandbook.com>
References:  <267B4CEEF5135C2FE0F2087E@mac-pro.magehandbook.com>

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On 5 May 2011 00:17, Daniel Staal <DStaal@usa.net> wrote:

>
> 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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I think you may be agonizing to much. You would have to to seriously bad to
make it slow and even then its a relative thing.

Giving it 4GB ZIL, 8 GB swap, and 28 gb l2arc will make it rapid and cover
you for most things. Putting the swap on the 250 gig drive wont make much
difference though as like you said you wont be paging to disk much

Put the bootblocks etc on the hd. They are only 64kb anyhow so will make no
noticable difference to the boot time. Also if your ssd dies you wont have
an unusable system (apart from a zil issue maybe)



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