Date: Fri, 22 Jan 1999 14:20:50 -0800 (PST) From: Pete Carah <pete@nntp1.interworld.net> To: freebsd-questions@FreeBSD.ORG Subject: Re: Writing a HUGE file to tape (SCSI, a DLT7000) Message-ID: <199901222220.OAA13418@nntp1.interworld.net> In-Reply-To: <19990108154736.L92409@freebie.lemis.com> References: <grog@lemis.com> <199901080349.VAA46613@nospam.hiwaay.net>
next in thread | previous in thread | raw e-mail | index | archive | help
In article <19990108154736.L92409@freebie.lemis.com> you write: > >On Thursday, 7 January 1999 at 21:49:24 -0600, David Kelly wrote: >> Greg Lehey writes: >>> On Wednesday, 6 January 1999 at 18:33:15 -0600, David Kelly wrote: >>>> To write a tar file larger than 2G on an SGI system requires a special >>>> option to SGI's tar. Wonder if FreeBSD's GNU tar has a 2G filesize >>>> limit? >>> >>> No. >> >> I didn't word things right. Correct wording is, "To write a file larger >> than 2G with tar on an SGI system..." The way I said it before suggests >> the tar archive itself was limited to 2G without the special option. > >Well, in fact the problem isn't with tar, it's with System V's file >systems, which still limit files to 2 GB, and usually even the file >systems can't be larger, though I believe there are exceptions. > >Of course, this means that having files larger than 2 GB limits their >portability. Actually, SGI has supported filesystems up to 8gb since irix 4.x; with 5.2 (or so) they introduced xfs which has no practical limit (it's at least 300gb for both files and filesystems since I have such a filesystem in a video lab I work with (40-way striped fiberchannel on 4 controllers; does 300megabytes/sec reading to memory). Note that since irix 3.x (late 1980's) sgi has not used anything resembling a sys5 file system (efs is basically an extent-based ufs, and xfs is a partly log-structured version of that with 64bit pointers (grossly oversimplified). Sun has esentially never used a sys5 file system (always ufs), and still stops at 2gb for files (but not filesystems; those had no limitations that I could find even under solaris 2.3). (actually they finally went to 64-bit internal inode values in 2.6 so they no longer have a practical limit either.) Also, I seem to recall writing more than 8g on a *tape* on an sgi under 4.0.5 when filesystems certainly were limited to that. It required tar'ing multiple mount points (obviously). Since irix 6.x now defaults to xfs these limitations no longer apply. The reason sgi uses extent-based file systems is that they are optimized for streaming video; the extent-based systems are very suboptimal for things like netnews. One problem with DLTs is that the system tape parms often don't match the drive config. (density settings vs minor number; this normally happens on both Sun and SGIs; I'd expect it on FBSD too.) Also the drives go bad with much use (make 4-5 tapes/day and the drive won't last a year; similar to exabyte.) In particular, if you try to use a fixed-block driver on a DLT the tape won't hold anything like its real capacity (picture inter-block gaps 10x longer than the data :-) This last may well be your problem. man mt has *some* pointers to the meaningful datatypes and the Quantum web site has *some* info on what the proper ansi format designators are for their drives (*very* indirect; it is not easy to find. I tend to copy a sun or sgi kernel-format string and hand interpret it). For more fun, try to tar the above video filesystem... There is currently only one (commercial) tape drive out there that will do it, from Ampex, and VERY expensive. (well, DLT jukeboxes can (barely) do it, but it takes a while...) -- Pete To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199901222220.OAA13418>