Date: Thu, 28 Aug 2014 10:27:59 -0400 From: Paul Kraus <paul@kraus-haus.org> To: Scott Bennett <bennett@sdf.org> Cc: freebsd-questions@freebsd.org, freebsd@qeng-ho.org, Trond.Endrestol@fagskolen.gjovik.no Subject: Re: gvinum raid5 vs. ZFS raidz Message-ID: <25B567A0-6639-41EE-AB3E-96AFBA3F11B7@kraus-haus.org> In-Reply-To: <201408280636.s7S6a5OZ022667@sdf.org> References: <201408020621.s726LsiA024208@sdf.org> <alpine.BSF.2.11.1408020356250.1128@wonkity.com> <53DCDBE8.8060704@qeng-ho.org> <201408060556.s765uKJA026937@sdf.org> <53E1FF5F.1050500@qeng-ho.org> <201408070831.s778VhJc015365@sdf.org> <alpine.BSF.2.11.1408071034510.64214@mail.fig.ol.no> <201408070936.s779akMv017524@sdf.org> <alpine.BSF.2.11.1408071226020.64214@mail.fig.ol.no> <201408071106.s77B6JCI005742@sdf.org> <5B99AAB4-C8CB-45A9-A6F0-1F8B08221917@kraus-haus.org> <201408220940.s7M9e6pZ008296@sdf.org> <7971D6CA-AEE3-447D-8D09-8AC0B9CC6DBE@kraus-haus.org> <201408260641.s7Q6feBc004970@sdf.org> <9588077E-1198-45AF-8C4A-606C46C6E4F8@kraus-haus.org> <201408280636.s7S6a5OZ022667@sdf.org>
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On Aug 28, 2014, at 2:36, Scott Bennett <bennett@sdf.org> wrote: > Paul Kraus <paul@kraus-haus.org> wrote: >> Wow. That implies you are hitting a drive with a very high = uncorrectable error rate since the drive did not report any errors and = the data is corrupt. I have yet to run into one of those. >=20 > How would an uncorrectable error be detected by the drive without = any > parity checking or hardware-implemented write-with-verify? I suppose my point was that an operation that is NOT flagged by the = drive as failing and DOES return faulty data is, by definition, an = uncorrectable error (as far as the drive is concerned). The point is = that an uncorrectable error (from the drive standpoint) is just that, an = error that the drive CANNOT detect. > Are you using any drives larger than 1 TB? I have been testing with a bunch of 2TB (3 HGST and 1 WD). I have been = using ZFS and it has not reported *any* checksum errors. I have put one of the 4 into production service (I needed a replacement = for a failed 1TB and did not have any more 1TB in stock). It has been = running for a couple weeks now with no checksum errors reported. My = zpool is 5 x 1TB RAIDz2 and it has about 2TB of data on it right now. > If so, try copying a 1.1 TB > file to one of them, and then trying comparing the copy against the = original. Hurmmm. I have not worked with individual files that large. What = filesystem are you using here?=20 > Out of the three drives I could test that way, I got that kind of = result on > two every time I tried it. One of the two was a new Samsung (i.e., a > Seagate), and the other was a refurbished Seagate supplied as a = replacement > under warranty. The third got a clean copy the first time and two = bytes with > single-bit errors on the second try. That one was also a refurbished = Seagate > provided under warranty. If you use ZFS on these drives and copy the same file do you get any = checksum errors? -- Paul Kraus paul@kraus-haus.org
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