Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: =?UTF-8?Q?Arne_Vajh=C3=B8j?= <arne@vajhoej.dk>
Newsgroups: comp.os.vms
Subject: Re: RX2800 sporadic disk I/O slowdowns
Date: Sun, 20 Oct 2024 19:08:41 -0400
Organization: A noiseless patient Spider
Lines: 20
Message-ID: <vf42hq$k0cc$1@dont-email.me>
References: <veu99d$3derp$1@dont-email.me> <veumb8$3gbt8$1@dont-email.me>
 <vf1ku6$3vhv$1@dont-email.me> <vf1lvv$3s2a$1@dont-email.me>
 <vf1m6n$444r$2@dont-email.me> <vf1mi6$3s2a$2@dont-email.me>
 <vf1nhv$444r$8@dont-email.me> <vf1nof$3s2a$3@dont-email.me>
 <vf1uo4$8qpm$2@dont-email.me> <vf2vsv$dvmh$1@dont-email.me>
 <vf3rvn$itru$1@dont-email.me> <vf3sbs$iugp$1@dont-email.me>
 <vf3tdg$itru$10@dont-email.me>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Injection-Date: Mon, 21 Oct 2024 01:08:42 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="e557ab2ded888c175ae698c2a2678a45";
	logging-data="655756"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX18oUryt5KMs0Gvkl4r1DdPodNJrJNmnlo8="
User-Agent: Mozilla Thunderbird
Cancel-Lock: sha1:1/92roK/K47KnRQgNMZpGOVrZzI=
In-Reply-To: <vf3tdg$itru$10@dont-email.me>
Content-Language: en-US
Bytes: 2127

On 10/20/2024 5:41 PM, Lawrence D'Oliveiro wrote:
> On Sun, 20 Oct 2024 17:23:08 -0400, Arne Vajhøj wrote:
>> Loss of completed/committed data is the problem.
> 
> The problem is not data loss, it is loss of data integrity. This is why we
> have transactions in databases and filesystems: on a crash or loss of
> power, we want transactions to be either completely lost or completely
> saved, not in some in-between incomplete state.
> 
> There is no caching disk controller that knows how to ensure this.

Let me try again.

DB write to plates & system crash => OK but slow
DB write to OS cache & system crash => potential problem with transaction
DB write to RAID controller with battery backup & system crash => OK and 
fast

Arne