Date: Mon, 13 Jul 2009 10:46:26 -0700 (PDT) From: Richard Mahlerwein <mahlerrd@yahoo.com> To: Free BSD Questions list <freebsd-questions@freebsd.org> Subject: Re: ZFS or UFS for 4TB hardware RAID6? Message-ID: <78927.1741.qm@web51001.mail.re2.yahoo.com>
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--- On Mon, 7/13/09, Richard Mahlerwein <mahlerrd@yahoo.com> wrote:=0A=0A> = From: Richard Mahlerwein <mahlerrd@yahoo.com>=0A> Subject: Re: ZFS or UFS f= or 4TB hardware RAID6?=0A> To: "Free BSD Questions list" <freebsd-questions= @freebsd.org>=0A> Date: Monday, July 13, 2009, 1:29 PM=0A> --- On Sun, 7/12= /09, Maxim Khitrov=0A> <mkhitrov@gmail.com>=0A> wrote:=0A> =0A> > From: Max= im Khitrov <mkhitrov@gmail.com>=0A> > Subject: ZFS or UFS for 4TB hardware = RAID6?=0A> > To: "Free BSD Questions list" <freebsd-questions@freebsd.org>= =0A> > Date: Sunday, July 12, 2009, 11:47 PM=0A> > Hello all,=0A> > =0A> > = I'm about to build a new file server using 3ware=0A> 9690SA-8E=0A> > contro= ller=0A> > and 4x Western Digital RE4-GP 2TB drives in RAID6. It=0A> is=0A>= > likely to=0A> > grow in the future up to 10TB. I may use FreeBSD 8 on=0A= > this=0A> > one, since=0A> > the release will likely be made by the time t= his=0A> server=0A> > goes into=0A> > production. The question is a simple o= ne - I have no=0A> > experience with=0A> > ZFS and so wanted to ask for rec= ommendations of that=0A> versus=0A> > UFS2. How=0A> > stable is the impleme= ntation and does it offer any=0A> benefits=0A> > in my=0A> > setup (describ= ed below)?=0A> > =0A> > All of the RAID6 space will only be used for file= =0A> storage,=0A> > accessible=0A> > by network using NFS and SMB. It may b= e split into=0A> > separate=0A> > partitions, but most likely the entire ar= ray will be=0A> one=0A> > giant storage=0A> > area that is expanded every t= ime another hard drive=0A> is=0A> > added. The OS=0A> > and all installed a= pps will be on a separate software=0A> RAID1=0A> > array.=0A> > =0A> > Give= n that security is more important than=0A> performance,=0A> > what would be= =0A> > your recommended setup and why?=0A> > =0A> > - Max=0A> =0A> Your mil= eage may vary, but...=0A> =0A> I would investigate either using more spindl= es if you want=0A> to stick to RAID6, or perhaps using another RAID level i= f=0A> you will be with 4 drives for a while.=A0 The reasoning=0A> is that t= here's an overhead with RAID 6 - parity blocks are=0A> written to 2 disks, = so in a 4 drive combination you have 2=0A> drives with data and 2 with pari= ty.=A0 =0A> =0A> With 4 drives, you could get much, much higher performance= =0A> out of RAID10 (which is alternatively called RAID0+1 or=0A> RAID1+0 de= pending on the manufacturer and on how accurate=0A> they wish to be, and on= how they actually implemented it,=0A> too). This would also mean 2 usable = drives, as well, so=0A> you'd have the same space available in RAID10 as yo= ur=0A> proposed RAID6.=A0 =0A> =0A> I would confirm you can, on the fly, co= nvert from RAID10 to=0A> RAID6 after you add more drives.=A0 If you can not= , then=0A> by all means stick with RAID6 now!=0A> =0A> With 4 1 TB drives (= for simpler examples)=0A> RAID5 =3D 3 TB available, 1 TB worth used in "par= ity".=A0=0A> Fast reads, slow writes. =0A> RAID6 =3D 2 TB available, 2 TB w= orth used in "parity".=A0=0A> Moderately fast reads, slow writes.=0A> RAID1= 0 =3D 2 TB available, 2TB in duplicate copies (easier=0A> work than parity = calculations).=A0 Very fast reads,=0A> moderately fast writes.=0A> =0A> Whe= n you switch to, say, 8 drives, the numbers start to=0A> change a bit.=0A> = RAID5 =3D 7TB available, 1 lost.=0A> RAID6 =3D 6TB available, 2 lost.=0A> R= AID10 =3D 4TB available, 4 lost.=0A> =0A=0ASorry, consider myself chastised= for having missed the "Security is more important than performance" bit. I= tend toward solutions that show the most value, and with 4 drives, it seem= s that I'd stick with the same "data security" only pick up the free speed = of RAID10. Change when you get to 6 or more drives, if necessary.=0A=0AFor= data security, I can't answer for the UFS2 vs. ZFS. For hardware setup, l= et me amend everything I said above with the following:=0A=0ASince you are = seriously focusing on data integrity, ignore everything I said but make sur= e you have good backups! :)=0A=0ASorry, =0A-Rich=0A=0A=0A
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