Date: Wed, 03 Jul 2013 13:09:06 +0300 From: Alexandr <shuriku@shurik.kiev.ua> To: Fleuriot Damien <ml@my.gd> Cc: freebsd-fs@freebsd.org Subject: Re: Whole disk ZFS or -a4k partition Message-ID: <51D3F842.9050002@shurik.kiev.ua> In-Reply-To: <F05806B1-944D-4982-81F5-0893D9F6E0C4@my.gd> References: <51D3ED4F.5030102@shurik.kiev.ua> <F05806B1-944D-4982-81F5-0893D9F6E0C4@my.gd>
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03.07.2013 12:46, Fleuriot Damien пишет: > On Jul 3, 2013, at 11:22 AM, Alexandr <shuriku@shurik.kiev.ua> wrote: > >> Hello, community! >> >> I have a laptop with 2 disks - mSATA 32Gb SSD and 500Gb HDD. I plan to >> use SSD as whole disk ZFS pool with root and /usr partitions and 500Gb >> SATA as ZFS pool for /home and /var. My questions are: >> >> 1. Do I need to create a 4k aligned partition on HDD for zfs pool or >> best to use a whole disk? >> 2. Where the best place for swap - ssd or hdd? SSD is much faster, but >> with limited write life cycle. >> > > I advise against using the whole disk for the following reason: > > DISK1, manufacturer 1: 3tb (give or take) > DISK2, manufacturer 2: 3tb (give or take MINUS 10 BYTES) > > Et voila, you can't use DISK1 with DISK2 because DISK2 is 10 bytes smaller and won't fit. > > > When building RAID arrays, it's recommended to: > - use disks from different manufacturers > - use disks ordered at different times (for example half at T1, half at T2) > - shave a few MBs off your disks, so that they all present the same size > > > Here's an example from my nas at home: > > % gpart show /dev/ada6 > => 34 5860533101 ada6 GPT (2.7T) > 34 6 - free - (3.0k) > 40 102400 1 freebsd-ufs (50M) > 102440 5860430688 2 freebsd-zfs (2.7T) > 5860533128 7 - free - (3.5k) > > > Notice how the disk presents 5860533101 sectors of 512 bytes. > Also notice how I've shaved off 50mbytes in the first, unused partition. > > This way, if I replace a disk later on and the new disk only has, say 5860533095 512-byte sectors, I can still use it in my pool. > Thanks, but I haven't raid arrays in my setup. I have two different zpools on ssd and hard disk.
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