Agreed with single user or sequential I/O systems, but with highly concurrent random I/O, more is better. At some point with enough users even sequential I/O becomes "random".
________________________________ From: Rich <rl...@pacbell.net> To: Gary Gatten Cc: freebsd-questions@freebsd.org <freebsd-questions@freebsd.org> Sent: Mon Jul 26 19:57:28 2010 Subject: Re: 1 file system, 2 drives? ________________________________ From: Gary Gatten <ggat...@waddell.com> Cc: "freebsd-questions@freebsd.org" <freebsd-questions@freebsd.org> Sent: Mon, July 26, 2010 1:41:19 PM Subject: RE: 1 file system, 2 drives? >From my experience (YMMV), most RAID controllers will NOT redistribute the >existing data/files onto the newly added drives. So, if you have a (3) drive >RAID5 your file exists on all three drives, as does the parity data. If you >add (2) drives, your original files will not be on the new drives. New files >WILL use all (5) drives. IMHO it's best to backup the data (twice), create a >new volume on the new RAID, and restore the data. That said, maybe >better/newer RAID controllers will redistribute / balance existing data across >all drives in the array - I don't know for sure. Either way, backup your data >- twice! And make sure it can be restored! Just because the backup app SAYS >it's OK, it's NOT OK until it can be successfully restored! Also, if you go from (7) drives to (3), your I/O may suffer. Newer faster drives MAY make up the difference, or make up enough of it that it won't impact your client. Just be aware this is a potential issue. Generally speaking more spindles = more I/O's / sec. G >>Generally speaking more spindles = more I/O's / sec. and more chance for failure. After a certain point adding more drives to a RAID0 stripe doesn't buy you anything because the first one is ready for the next command before you get very far down the line. -----Original Message----- From: owner-freebsd-questi...@freebsd.org<mailto:owner-freebsd-questi...@freebsd.org> [mailto:owner-freebsd-questi...@freebsd.org<mailto:owner-freebsd-questi...@freebsd.org>] On Behalf Of John Almberg Sent: Monday, July 26, 2010 3:31 PM To: Chuck Swiger Cc: freebsd-questions@freebsd.org<mailto:freebsd-questions@freebsd.org> Subject: Re: 1 file system, 2 drives? > If you have hardware controller with RAID capabilities, using native RAID is > better, otherwise look towards gvinum or maybe ccd; see also: > I've just been reading up on RAID in my Absolute FreeBSD book, and it occurs to me that my client has a SCSI RAID drive chassis that he is using stupidly... It's a 14 bay drive, and he's currently got seven 32G drives stuck in it, configured with RAID-0. This is the original 200G drive I was talking about. It's a few years old. Over the next few years, this guy is going to need lots of storage for his videos. After a bit of reading, I'm wondering if the best idea might be to toss out those 32G drives and replace them with 3 big (say, 300G) drives configured with RAID-5. It sounds to me like a RAID-5 array can be expanded by adding new drives. QUESTION: is expansion normally a matter of just plugging in a new drive? Is the new drive automatically grafted onto the old drives? Or do you have to go through a process like, backing up the data, plugging in the new drive, reformatting the expanded array of drives, and restoring the data. I don't know the brand/model of the RAID drive chassis, but the client thinks it can be switched to use RAID 5. I'm waiting for the technical details, but assuming it can handle RAID-5 for now. Thanks: John _______________________________________________ freebsd-questions@freebsd.org<mailto:freebsd-questions@freebsd.org> mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "freebsd-questions-unsubscr...@freebsd.org<mailto:freebsd-questions-unsubscr...@freebsd.org>" <font size="1"> <div style='border:none;border-bottom:double windowtext 2.25pt;padding:0in 0in 1.0pt 0in'> </div> "This email is intended to be reviewed by only the intended recipient and may contain information that is privileged and/or confidential. If you are not the intended recipient, you are hereby notified that any review, use, dissemination, disclosure or copying of this email and its attachments, if any, is strictly prohibited. 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