linux-kernel - Re: [GIT PULL 18/25] lightnvm: set target over-provision on create ioctl

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <05ea1992-8dae-f961-b2e0-a93727edc2b5@bjorling.me>
Date:   Fri, 5 Jan 2018 20:53:53 +0100
From:   Matias Bjørling <m@...rling.me>
To:     Javier Gonzalez <javier@...xlabs.com>,
        Randy Dunlap <rdunlap@...radead.org>
Cc:     Jens Axboe <axboe@...com>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Hans Holmberg (C)" <hans.holmberg@...xlabs.com>
Subject: Re: [GIT PULL 18/25] lightnvm: set target over-provision on create
 ioctl

On 01/05/2018 08:52 PM, Javier Gonzalez wrote:
>> On 5 Jan 2018, at 20.33, Randy Dunlap <rdunlap@...radead.org> wrote:
>>
>> On 01/05/2018 05:16 AM, Matias Bjørling wrote:
>>> From: Javier González <javier@...xlabs.com>
>>>
>>> Allow to set the over-provision percentage on target creation. In case
>>> that the value is not provided, fall back to the default value set by
>>> the target.
>>>
>>> In pblk, set the default OP to 11% of the total size of the device
>>
>>> +#define PBLK_DEFAULT_OP (11)
>>
>> Hi,
>> Just curious -- where does 11 come from?  Is it a spec value?
> 
> 11 stands for 11% over-provisioning for the media to allow garbage
> collection. Different SSDs have different values based on the targeted
> workload - 11% is a common default value for standard drives.
> 
> The spec. does not specify any default values of over-provisioning.
> 
> Javier.
> 

I think what Randy means is, why is the value not 20% or 7%, which is 
the traditional over-provisioning on SSDs.