From: Andrei Borzenkov <arvidjaar@gmail.com>
To: Alberto Bursi <alberto.bursi@outlook.it>,
Qu Wenruo <quwenruo.btrfs@gmx.com>,
"linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>,
Linux FS Devel <linux-fsdevel@vger.kernel.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>
Subject: Re: Is it possible that certain physical disk doesn't implement flush correctly?
Date: Sun, 31 Mar 2019 15:21:46 +0300 [thread overview]
Message-ID: <8faff75a-21bb-b21b-b19b-fd5aad002b88@gmail.com> (raw)
In-Reply-To: <AM0PR03MB5745ACEC53F69BC28AC480F592540@AM0PR03MB5745.eurprd03.prod.outlook.com>
31.03.2019 14:27, Alberto Bursi пишет:
>
> On 30/03/19 13:31, Qu Wenruo wrote:
>> Hi,
>>
>> I'm wondering if it's possible that certain physical device doesn't
>> handle flush correctly.
>>
>> E.g. some vendor does some complex logical in their hdd controller to
>> skip certain flush request (but not all, obviously) to improve performance?
>>
>> Do anyone see such reports?
>>
>> And if proves to happened before, how do we users detect such problem?
>>
>> Can we just check the flush time against the write before flush call?
>> E.g. write X random blocks into that device, call fsync() on it, check
>> the execution time. Repeat Y times, and compare the avg/std.
>> And change X to 2X/4X/..., repeat above check.
>>
>> Thanks,
>> Qu
>>
>>
>
> Afaik HDDs and SSDs do lie to fsync()
>
> unless the write cache is turned off with hdparm,
I know at least one case of SSD that are claimed to flush cache in case
of power loss. I can dig up details if anyone is interested.
>
> hdparm -W0 /dev/sda
>
> similarly to RAID controllers.
>
> see below
>
> https://brad.livejournal.com/2116715.html
>
> https://queue.acm.org/detail.cfm?id=2367378
>
>
> -
>
next prev parent reply other threads:[~2019-03-31 12:21 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-30 12:31 Is it possible that certain physical disk doesn't implement flush correctly? Qu Wenruo
2019-03-30 12:57 ` Supercilious Dude
2019-03-30 13:00 ` Qu Wenruo
2019-03-30 13:04 ` Supercilious Dude
2019-03-30 13:09 ` Qu Wenruo
2019-03-30 13:14 ` Supercilious Dude
2019-03-30 13:24 ` Qu Wenruo
2019-03-31 22:45 ` J. Bruce Fields
2019-03-31 23:07 ` Alberto Bursi
2019-03-31 11:27 ` Alberto Bursi
2019-03-31 12:00 ` Qu Wenruo
2019-03-31 13:36 ` Hannes Reinecke
2019-03-31 14:17 ` Qu Wenruo
2019-03-31 14:37 ` Hannes Reinecke
2019-03-31 14:40 ` Qu Wenruo
2019-03-31 12:21 ` Andrei Borzenkov [this message]
2019-04-01 11:55 ` Austin S. Hemmelgarn
2019-04-01 12:04 ` Austin S. Hemmelgarn
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