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From: Scott Ribe <[email protected]>
To: Gogala, Mladen (Short Hills) <[email protected]>
Cc: pgsql-admin <[email protected]>
Subject: Re: regarding PG on ZFS performance
Date: Tue, 12 Apr 2022 13:48:30 -0600
Message-ID: <[email protected]> (raw)
In-Reply-To: <MN2PR10MB414452D25260BD09F6685C718AED9@MN2PR10MB4144.namprd10.prod.outlook.com>
References: <[email protected]>
	<MN2PR10MB414452D25260BD09F6685C718AED9@MN2PR10MB4144.namprd10.prod.outlook.com>

> On Apr 12, 2022, at 10:54 AM, Gogala, Mladen (Short Hills) <[email protected]> wrote:
> 
> I wouldn’t call turning off data safety “a proper tuning”. It may be faster but can never be deployed to production.

As I explained, that which it protects against cannot happen on a ZFS volume. Therefore turning it off is just fine.

(ZFS fsync operations are themselves atomic, using its own write-ahead log. So full_page_writes does a double write to avoid corruption, but so does ZFS, thus 4X writes, and a major source of slowness. There is NO danger in letting only one of the two do a double-write in order to avoid a partial write ever being read back.)

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