From: Brendan Hide <brendan@swiftspirit.co.za>
To: Austin S Hemmelgarn <ahferroin7@gmail.com>,
Tomasz Chmielewski <tch@virtall.com>,
Calvin Walton <calvin.walton@kepstin.ca>
Cc: "linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>
Subject: Re: RAID-1 - suboptimal write performance?
Date: Sun, 18 May 2014 20:49:53 +0200 [thread overview]
Message-ID: <537900D1.6060802@swiftspirit.co.za> (raw)
In-Reply-To: <537684F9.6060909@gmail.com>
On 2014/05/16 11:36 PM, Austin S Hemmelgarn wrote:
> On 05/16/2014 04:41 PM, Tomasz Chmielewski wrote:
>> On Fri, 16 May 2014 14:06:24 -0400
>> Calvin Walton <calvin.walton@kepstin.ca> wrote:
>>
>>> No comment on the performance issue, other than to say that I've seen
>>> similar on RAID-10 before, I think.
>>>
>>>> Also, what happens when the system crashes, and one drive has
>>>> several hundred megabytes data more than the other one?
>>> This shouldn't be an issue as long as you occasionally run a scrub or
>>> balance. The scrub should find it and fix the missing data, and a
>>> balance would just rewrite it as proper RAID-1 as a matter of course.
>> It's similar (writes to just one drive, while the other is idle) when
>> removing (many) snapshots.
>>
>> Not sure if that's optimal behaviour.
>>
> [snip]
>
> Ideally, BTRFS should dispatch the first write for a block in a
> round-robin fashion among available devices. This won't fix the
> underlying issue, but it will make it less of an issue for BTRFS.
>
More ideally, btrfs should dispatch them in parallel. This will likely
be looked into for N-way mirroring. Having 3 or more copies and working
in the current way would be far from optimal.
--
__________
Brendan Hide
http://swiftspirit.co.za/
http://www.webafrica.co.za/?AFF1E97
next prev parent reply other threads:[~2014-05-18 18:50 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-16 15:48 RAID-1 - suboptimal write performance? Tomasz Chmielewski
2014-05-16 18:06 ` Calvin Walton
2014-05-16 20:41 ` Tomasz Chmielewski
2014-05-16 21:36 ` Austin S Hemmelgarn
2014-05-18 18:49 ` Brendan Hide [this message]
2014-05-23 12:57 ` Roman Mamedov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=537900D1.6060802@swiftspirit.co.za \
--to=brendan@swiftspirit.co.za \
--cc=ahferroin7@gmail.com \
--cc=calvin.walton@kepstin.ca \
--cc=linux-btrfs@vger.kernel.org \
--cc=tch@virtall.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).