Date: Mon, 22 Jun 2015 17:03:12 -0400 From: Quartz <quartz@sneakertech.com> To: Xin Li <delphij@delphij.net> Cc: FreeBSD FS <freebsd-fs@freebsd.org> Subject: Re: ZFS raid write performance? Message-ID: <55887810.3080301@sneakertech.com> In-Reply-To: <5587C97F.2000407@delphij.net> References: <5587C3FF.9070407@sneakertech.com> <5587C97F.2000407@delphij.net>
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>> What's sequential write performance like these days for ZFS >> raidzX? Someone suggested to me that I set up a single not-raid >> disk to act as a fast 'landing pad' for receiving files, then move >> them to the pool later in the background. Is that actually >> necessary? (Assume generic sata drives, 250mb-4gb sized files, and >> transfers are across a LAN using single unbonded GigE). > > That sounds really weird recommendation IMHO. Did "someone" explained > with the reasoning/benefit of that "landing pad"? Sort of. Something about the checksum calculations causing too much overhead. I think they were confused about sequential write vs random write, and possibly mdadm vs zfs. It was just something mentioned in passing that I didn't want to start a debate about at the time, since I wasn't 100% sure. >a single hard drive won't do much beyond 100MB/s (maybe > 120MB/s max) for sequential 128kB blocks, so that "landing pad" would > probably not very helpful assuming you can saturate your GigE network Wait, I'm confused. A single GigE has a theoretical max of like 100mb/sec. That would imply the drive is probably about the same speed?
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