Date: Wed, 9 Jul 2008 18:02:18 -0700 From: "Jeff Mohler" <speedtoys.racing@gmail.com> To: "Alexandre Biancalana" <biancalana@gmail.com> Cc: freebsd-fs@freebsd.org, juri_mian@yahoo.com Subject: Re: 24 TB UFS2 reality check ? Message-ID: <a969fbd10807091802r20880a9am241bf4c100d29f45@mail.gmail.com> In-Reply-To: <8e10486b0807091759m7cf4a04dsa4538594bc4a9304@mail.gmail.com> References: <a969fbd10807081925o1ee3b70cn772ca48d3afb393@mail.gmail.com> <947384.22013.qm@web45601.mail.sp1.yahoo.com> <8e10486b0807091759m7cf4a04dsa4538594bc4a9304@mail.gmail.com>
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Lets see..a peak of maybe 25-30 random drive IOPS/sec at 15ms MINIMAL latency per IO (likely more like 35-40)..gonna be ugly. Complicated by normal load IOPS..you could expect it all to simply "dissapear" for a day while it reconstructs. On Wed, Jul 9, 2008 at 5:59 PM, Alexandre Biancalana <biancalana@gmail.com> wrote: > On 7/9/08, Juri Mianovich <juri_mian@yahoo.com> wrote: >> >> Hello Jeff, >> >> >> --- On Tue, 7/8/08, Jeff Mohler <speedtoys.racing@gmail.com> wrote: >> >> >> >> > One drive has a what..maybe a 1 per 1.0 E15 bits transferred >> > uBER, and >> > you have 24x that of one drive, as each drive it it's >> > statistical crap >> > shoot. Each drive may NEVER hit uBER for you, but one may >> > do it >> > tomorrow. >> > >> > Plus, you have commodity firmware levels on those drives >> > and commodity >> > BER mechanisms, so you COULD argue you have another 2x >> > liability WRT >> > losing it all without HEFTY raid, at least 5+1. >> >> >> >> Thank you - I understand. You are worried because of the lack of redundancy. >> >> I didn't want to make my questions any more complicated than they were, but since we are on the topic, I will tell you that _in reality_ I will not make a 24 TB array, I will in fact use the raid-6 functionality (two parity drives) of my card and make a ~22 TB array. >> >> Does that address the concerns you were raising ? Does 22 data and 2 parity (raid 6) still make you very nervous, or does that completely change the scenario you were worried about ? > > > I did be fewer nervous if you do 2 arrays of 11 disks... what`s the > time that it will take to do a rebuild of a failed drive in your > normal load ?? >
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