Date: Thu, 24 Sep 2015 22:05:36 -0400 From: Quartz <quartz@sneakertech.com> To: FreeBSD questions <freebsd-questions@freebsd.org> Subject: Re: sync vs async vs zfs Message-ID: <5604ABF0.3060007@sneakertech.com> In-Reply-To: <BB74A712-819C-4FD9-9FB1-A5A456731AC8@kraus-haus.org> References: <56042774.6070404@sneakertech.com> <98BFE313-523F-4A2C-82BB-8683466068FB@kraus-haus.org> <560462C4.6030106@sneakertech.com> <BB74A712-819C-4FD9-9FB1-A5A456731AC8@kraus-haus.org>
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> I expect that system utilities like cp and tar do not do sync writes. > sync writes are supposed to be a special case, used only when needed. > I run into them with VBox writing to<>.vmdk files. NFS forces sync though, doesn't it? What if you're cp-ing to a mounted share? I'm not sure I totally understand how all this interacts. >> 2) Async doesn't really care how your pool is constructed, and a >> SLOG is really the only thing that seriously makes a difference for >> sync, correct? > > Not quite true. Once you get through the ARC the configuration of the > zpool _will_ matter to performance. Maybe I worded that badly. What I meant was that whereas sync write performance is strongly affected by a SLOG, async writes have no special considerations of their own that don't also affect sync, right?
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