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- From: brydon@asl.slb.com (Harvey Brydon (918)250-4312)
- Subject: Re: Problems with EXABYTE tape drive
- Message-ID: <1993Jan23.124519.7098@slcs.slb.com>
- Sender: news@slcs.slb.com (News Administrator)
- Nntp-Posting-Host: 129.87.186.2
- Reply-To: brydon@dsn.SINet.slb.com
- Organization: Dowell Schlumberger, Tulsa, Oklahoma
- References: <1993Jan22.200938.22220@das.harvard.edu>
- Date: Sat, 23 Jan 93 12:45:19 GMT
- Lines: 27
-
- In article <1993Jan22.200938.22220@das.harvard.edu>, chen@speed.uucp (Lilei
- Chen) writes:
- >On our site we use EXABYTE tape drive for backup purpose. But we
- >can not get more than 500MB on a 112M tape which is supposed to be
- >able to hold more than 2GB according to the specification. We have
- >about five drives and all behave the same way. We even tried it on
- >a PC with an ADAPTEC SCSI controler, but the result is the same.
- >EXABYTE claimed that they don't know anything about the possible
- >cause. So I am asking the net if anyone has encountered similar
- >problems with EXABYTE tape drive and/or knows its possible cause.
- >Thanks.
-
- This is a helical scan tape drive that works in 'stream' mode. What that
- means is that as long as you are feeding it data, it will write to tape (no
- surprise there) but if you stop feeding it data and the drive needs more to
- write, it writes filler info to the tape. You therefore get less capacity on
- the tape if you can't keep the drive busy. This will happen for example if
- you have a highly fragmented disk (image or incremental backup) or if the
- backup process runs at a low scheduling priority on a busy system. Backing up
- (image) a compressed disk should give you better tape usage, as will a
- physical backup. Incrementals will give you the least efficient tape usage.
-
- HTH
- _______________________________________________________________
- Harvey Brydon | Internet: brydon@dsn.SINet.slb.com
- Dowell Schlumberger | P.O.T.S.: (918)250-4312
- Backup my system disk? Okay, where's the reverse switch?
-