zfs arc and amount of wired memory

Alexander Leidinger Alexander at Leidinger.net
Thu Feb 9 13:48:53 UTC 2012


this only applies to old systems (slooow disks, no NCQ support), or very fast USB3 memory sticks. Current (I would say at least 2-3 year old) hardware is slowed down by USB2.


Send via an Android device, please forgive brevity and typographic and spelling errors. 

Freddie Cash <fjwcash at gmail.com> hat geschrieben:On Wed, Feb 8, 2012 at 10:40 AM, Freddie Cash <fjwcash at gmail.com> wrote:
> On Wed, Feb 8, 2012 at 10:25 AM, Eugene M. Zheganin <emz at norma.perm.ru> wrote:
>> On 08.02.2012 18:15, Alexander Leidinger wrote:
>>> I can't remember to have seen any mention of SWAP on ZFS being safe
>>> now. So if nobody can provide a reference to a place which tells that
>>> the problems with SWAP on ZFS are fixed:
>>>  1. do not use SWAP on ZFS
>>>  2. see 1.
>>>  3. check if you see the same problem without SWAP on ZFS (btw. see 1.)
>> So, if a swap have to be used, and, it has to be backed up with something
>> like gmirror so it won't come down with one of the disks, there's no need to
>> use zfs for system.
>> This makes zfs only useful in cases where you need to store something on a
>> couple+ of terabytes, still having OS on ufs. Occam's razor and so on.
> Or, you plug a USB stick into the back (or even inside the case as a
> lot of mobos have internal USB connectors now) and use that for swap.

That also works well for adding L2ARC (cache) to the ZFS pool as well.

Freddie Cash
fjwcash at gmail.com
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