Joshua Baker-LePain wrote:
> On Wed, 28 Mar 2007 at 10:07pm, Mark Schoonover wrote
>
>> Having used a 20 tape library, and suffering through restores with
>> AIT2 tapes taking 10-12 hours per tape, I gave up on them. I went
>> with good old
>
> One of the lovely bits about LTO3 -- 400GB native, 80MB/s => restore a
> whole tape in under 2 hours.
Joshua,
200 gigs an hour is pretty good for a tape, but what happens if the
tape you've backed up to is bad, or has a bad spot? You've lost your backup.
400GB in drives is a fraction of the cost of tapes these days. I do agree,
my max throughput over a quiet gigbit network is going to be around half the
speed of the LTO, I look at the fact that I'm only backing up the daily
changes, not an entire server like you'd do to tape. With rsync doing
compression over SSH, it looks like I'm backing up an entire 1.3TB system in
90 mins. Sure, you can do differental backups to try to keep your number of
tapes to a minimum. Backing up straight to disk ends up being faster all
around, plus it's on a RAID5 system so loosing a drive isn't all that big a
deal. Going to disk is also fast enough, I can run hourly backups during
business hours.
Where LTO tapes will outrun is during a total server failure where I
have to restore all data back to a server. Then my network becomes the
bottleneck, but you still won't have to gamble spanning across multiple
tapes to fit >400GB of data. My past problems have never been with backing
up, it's been with restoring the data. Either too slow to restore, or since
I needed 10 tapes to backup, I'd end up with one of them having a bad spot
that would abort the restore. The only way to know for sure if your tapes
are 100% is to try to do an entire restoration. Simply running a tape verify
isn't enough.
Cost is another factor. An Exabyte LTO3 1x7 loader is MSRP $6500,
with 20 tapes $1130 in a pack. My 4TB backup server cost just under $5000 at
the time, cheaper today. Then, you have the daily admin of flipping tapes.
Disks run without intervention once configured, and it's nice to have
especially if you have employees working over the weekends, or on holidays.
These were just my requirements, and my thought processes that lead
me away from tapes all together. YMMV, your specifics are probably
different.
Mark
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