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Re: [PATCH] mkfs: default to CRC enabled filesystems

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH] mkfs: default to CRC enabled filesystems
From: Linda Walsh <xfs@xxxxxxxxx>
Date: Thu, 19 Mar 2015 19:27:25 -0700
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1426720967-8215-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1426720967-8215-1-git-send-email-david@xxxxxxxxxxxxx>
User-agent: Thunderbird
Dave Chinner wrote:
From: Dave Chinner <dchinner@xxxxxxxxxx>

It's time to change the mkfs defaults to enable CRCs for all new
filesystems.
---
        "Sounds good", but what exactly is CRC'ed?

I.e. all data? Or how much data/second would I expect
to 'need' CRC'ing?

Some quick timing stuff:

time dd if=/dev/zero of=1G bs=1M count=1024 oflag=direct
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 1.76947 s, 607 MB/s
1.77sec 0.00usr 0.50sys (28.38% cpu)

dropcaches
76.34sec 0.00usr 69.22sys (90.69% cpu)

Ishtar:law/bin> time crc32 1G                ## no cache
5B64C2B0
6.67sec 3.85usr 0.94sys (71.82% cpu)

time crc32 1G                           ## in cache
5B64C2B0
4.00sec 3.57usr 0.42sys (100.00% cpu)
(using Xeon X5660 @ 2.80GHz)


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