Date: Fri, 19 Jul 2013 11:25:28 -0700 From: aurfalien <aurfalien@gmail.com> To: Warren Block <wblock@wonkity.com> Cc: freebsd-questions@freebsd.org, Shane Ambler <FreeBSD@ShaneWare.Biz> Subject: Re: to gmirror or to ZFS Message-ID: <069F4A27-A7A2-4215-A815-468F436B331F@gmail.com> In-Reply-To: <alpine.BSF.2.00.1307161239580.82091@wonkity.com> References: <4DFBC539-3CCC-4B9B-AB62-7BB846F18530@gmail.com> <alpine.BSF.2.00.1307152211180.74094@wonkity.com> <976836C5-F790-4D55-A80C-5944E8BC2575@gmail.com> <51E51558.50302@ShaneWare.Biz> <C13CC733-E366-4B54-8991-0ED229932787@gmail.com> <alpine.BSF.2.00.1307161239580.82091@wonkity.com>
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On Jul 16, 2013, at 11:42 AM, Warren Block wrote:
> On Tue, 16 Jul 2013, aurfalien wrote:
>> On Jul 16, 2013, at 2:41 AM, Shane Ambler wrote:
>>>
>>> I doubt that you would save any ram having the os on a non-zfs drive as
>>> you will already be using zfs chances are that non-zfs drives would only
>>> increase ram usage by adding a second cache. zfs uses it's own cache
>>> system and isn't going to share it's cache with other system managed
>>> drives. I'm not actually certain if the system cache still sits above
>>> zfs cache or not, I think I read it bypasses the traditional drive cache.
>>>
>>> For zfs cache you can set the max usage by adjusting vfs.zfs.arc_max
>>> that is a system wide setting and isn't going to increase if you have
>>> two zpools.
>>>
>>> Tip: set the arc_max value - by default zfs will use all physical ram
>>> for cache, set it to be sure you have enough ram left for any services
>>> you want running.
>>>
>>> Have you considered using one or both SSD drives with zfs? They can be
>>> added as cache or log devices to help performance.
>>> See man zpool under Intent Log and Cache Devices.
>>
>> This is a very interesting point.
>>
>> In terms if SSDs for cache, I was planning on using a pair of Samsung Pro 512GB SSDs for this purpose (which I haven't bought yet).
>>
>> But I tire of buying stuff, so I have a pair of 40GB Intel SSDs for use as sys disks and several Intel 160GB SSDs lying around that I can combine with the existing 256GB SSDs for a cache.
>>
>> Then use my 36x3TB for the beasty NAS.
>
> Agreed that 256G mirrored SSDs are kind of wasted as system drives. The 40G mirror sounds ideal.
Update;
I went with ZFS as I didn't want to confuse the toolset needed to support this server. Although gmirror is not hard to figure out, I wanted consistency in systems.
So I've a booted 9.1 rel using a mirrored ZFS system disk.
The drives do support TRIM but am unsure how this plays with ZFS. I did the standard partition scheme of;
root@kronos:/root # gpart show
=> 34 78165293 da0 GPT (37G)
34 128 1 freebsd-boot (64k)
162 6 - free - (3.0k)
168 8388608 2 freebsd-swap (4.0G)
8388776 69776544 3 freebsd-zfs (33G)
78165320 7 - free - (3.5k)
=> 34 78165293 da1 GPT (37G)
34 128 1 freebsd-boot (64k)
162 6 - free - (3.0k)
168 8388608 2 freebsd-swap (4.0G)
8388776 69776544 3 freebsd-zfs (33G)
78165320 7 - free - (3.5k)
At any rate, thank you for the replies, very much appreciate it.
Especially since building a rather large production worthy NAS not knowing a lick of freeBSD.
The reasons going with freeBSD are 2 fold;
ZFS stability,seems a better marriage then ZOL.
Correctly provides NFS pre attributes on write reply; mtime. Linux does not.
While its a steep learning curve, the 2 points above require the use of freeBSD or alike.
- aurf
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