linux-kernel - Re: wishful thinking about atomic, multi-sector or full MD stripe width, writes in storage

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <m33a73oael.fsf@intrepid.localdomain>
Date:	Fri, 04 Sep 2009 01:50:42 +0200
From:	Krzysztof Halasa <khc@...waw.pl>
To:	Ric Wheeler <rwheeler@...hat.com>
Cc:	Christoph Hellwig <hch@...radead.org>, Mark Lord <lkml@....ca>,
	Michael Tokarev <mjt@....msk.ru>, david@...g.hm,
	Pavel Machek <pavel@....cz>, Theodore Tso <tytso@....edu>,
	NeilBrown <neilb@...e.de>, Rob Landley <rob@...dley.net>,
	Florian Weimer <fweimer@....de>,
	Goswin von Brederlow <goswin-v-b@....de>,
	kernel list <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>, mtk.manpages@...il.com,
	rdunlap@...otime.net, linux-doc@...r.kernel.org,
	linux-ext4@...r.kernel.org, corbet@....net
Subject: Re: wishful thinking about atomic, multi-sector or full MD stripe width, writes in storage

Ric Wheeler <rwheeler@...hat.com> writes:

> The whole thread above is about software MD using commodity drives
> (S-ATA or SAS) without battery backed write cache.

Yes. However, you mentioned external RAID arrays disable disk caches.
That's why I asked if they are using SATA or SCSI/etc. disks, and if
they have battery-backed cache.

> Also, when you enable the write cache (MD or not) you are buffering
> multiple MB's of data that can go away on power loss. Far greater
> (10x) the exposure that the partial RAID rewrite case worries about.

The cache is flushed with working barriers. I guess it should be
superior to disabled WB cache, in both performance and expected disk
lifetime.
-- 
Krzysztof Halasa
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/