Date: Mon, 11 Oct 1999 07:49:00 -0700 From: Darryl Okahata <darrylo@sr.hp.com> To: freebsd-questions@FreeBSD.ORG Subject: Re: Why use tape for backups? (was: backup method reccommendation?) Message-ID: <199910111449.HAA09498@mina.sr.hp.com> In-Reply-To: Your message of "Sun, 10 Oct 1999 18:42:58 PDT."
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Brooks Davis <brooks@one-eyed-alien.net> wrote:
> On 10 Oct 1999, Arcady Genkin wrote:
>n
> > Is there any reasons tapes are a better choice?
>
> In summary, if you really care about your data, hard drives are likely a
> more expensive option. Anyway, who wants to end up with only one machine
> anyway. ;-)
Everything you've said is very true for a commercial enviroment,
but there's much to said for using a drive as an home backup device.
I'm using an IDE drive on a *separate* system as a backup device.
I just use "dump ... | gzip -9 | rsh ..." to do backups. Advantages:
* It's cheaper than a *good*, high-capacity tape drive. US$230 for a
5400 RPM 27GB IDE drive is a very good price point.
[ 5400RPM is good, because (1) you don't need the speed of a 7200RPM
drive for backups, and (2) 5400RPM drives run cooler. "Cooler is
better", because cooler drives tend to last longer, and because you
may have fewer cooling problems if you ever decide to put the IDE
drive into a cartridge module for drive swapping. ]
For simple home use, a couple of "dump 0"s and a few incrementals are
enough. However, if your home backup requirements need more than
this, then backing up to hard disks is probably not for you.
* It can be as fast as a *good*, high-capacity tape drive. Even with
'gzip -9', I'm getting around 490KB/sec; I recently backed up 8145292K
in 16605sec. If I was smart, and used lower compression, I could get
higher throughput (but I'd be limited by my 10BT network). If I used a
100BT LAN and was smart about compression, my backup system would
probably be faster than a low-end DLT system.
* You don't have to play tape swapping games to backup your system.
Most (all?), under US$500 (new) DAT drives have an uncompressed
capacity of 4GB or less, which is much smaller than an inexpensive IDE
drive. Yes, Travan-based drives are cheaper and hold more, but I'm
not sure I trust Travan drives.
* You can turn off the "backup system" to swap drives. I haven't done
this, but it wouldn't be difficult to make the IDE drive swappable.
IDE drive modules for swapping are widely available (the non-hot-
swappable ones, at least) and are inexpensive. Swapping drives
becomes easier if you have a separate drive for root (you might even
be able to use picobsd for that).
Disadvantages:
* If your backup drive crashes, you're screwed. In my case, I care
about the data on my main system, and, if the backup drive dies, I
just replace it and redo the backups (and pray that none of the disks
in my main system crashes in the meantime ;-). I've also thought
about using one of the "no-slot" IDE mirroring solutions (RAID 1) from
http://www.arcoide.com, but I don't know if it's really worth it *for
me*.
* If you use your backup system for version control ("help, I need the
version of xxx.c that existed on April 1!"), you're probably screwed.
You can't keep too many backups on an hard drive.
* Off-site backups can be difficult. If your house burns down, you're
really screwed. ;-(
Still, for "simple home use", an hard disk backup device is often "good
enough". I would defintely not use or recommend it for commercial or
business purposes, though.
--
Darryl Okahata
darrylo@sr.hp.com
DISCLAIMER: this message is the author's personal opinion and does not
constitute the support, opinion, or policy of Hewlett-Packard, or of the
little green men that have been following him all day.
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