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janc
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New Tape Drive for Grex?
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Jul 26 16:08 UTC 2000 |
At the board meeting STeve proposed that we purchase a new tape backup system
for Grex.
The issue is fairly urgent because we don't have a working tape drive right
now and haven't been doing backups for a while. Likely our old drive can be
repaired, but it is also a bit low capacity, so several tapes are needed to
do a backup, and it is slow. This means lots of downtime for backups, and
it means someone has to hang around to change tapes, making it even more of
a pain in the keester.
STeve proposed buying a fairly serious tape backup system. Something fast,
high capicity, reliable. Something where we could do daily snapshots as well
as regular full backups.
He brought to the meeting some data sheets for a drive he liked:
Exabyte Mammoth Tape Drive
20 GB capability, (40 GB compressed)
180 MB-per-minute transfer rate (360 MB-per-minute compressed)
8mm tapes (could read our old backup tapes)
SCSI (should work easily with our system)
Data sheets are at http://www.exabyte.com/products/8mm/mammoth/
Media costs are pretty modest, like $12 a tape.
The drive is something like $1400.
Discussion invited.
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| 79 responses total. |
scott
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response 1 of 79:
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Jul 26 16:39 UTC 2000 |
Hmmm...
Our hardware costs have been rather impressively low/zero lately, so it's
probably time.
Our current drive takes about 5-6 hours total to back up Grex, including 2
tape changes. This is time when somebody has to show up to change tapes
(ugh), and grex has to be down for the duration (ick).
I'd probably go for it. Pity we couldn't find something a little less cutting
edge/ expensive, though.
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albaugh
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response 2 of 79:
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Jul 26 16:44 UTC 2000 |
I 2nd Scott's sentiments: A fair chunk of change, compared to grex's assets.
But it's an important function.
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janc
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response 3 of 79:
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Jul 26 16:58 UTC 2000 |
Just did a little web searching looking for a price on this. Most places say
$call, and I'm too lazy.
http://www.ePCDeals.com/shop/SearchResults.asp?ProdStock=896111%2D255
quotes $1895.00. That's the lowest price one of these price comparison
sites could find. List prices seem to be $3600 to $4000.
A better choice might be the Mammoth LT:
http://www.exabyte.com/products/mammoth/mamlt/datamlt.html
It's an 8mm Exabyte SCSI internal drive holding 14GB native (28GB compressed).
Data rate is 7.2 GB-per-hour (120-MB-per-minute). List is $1617.
This place sells it for $1095.95
http://www.us.buy.com/retail/product.asp?sku=10025706&loc=101
Media cost looks higher than we said. I haven't done a full search on this
though. The two tapes recommended for the Mammoth LT seem to be around
$20 and $40 respectively (dunno if the lower priced tape holds the full
14GB). The tapes for the Mammoth seem to be around $60. This is for
name brand ExaTape tapes, and I haven't done much shopping around.
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rcurl
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response 4 of 79:
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Jul 26 17:02 UTC 2000 |
Is a CD-ROM an option?
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other
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response 5 of 79:
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Jul 26 18:03 UTC 2000 |
Not really. The media hasn't the proven track record of reliability, and the
capacity is way too small. Tape backup is an established and proven reliable
standard. CD makes sense for home computers with smaller capacity and less
frequent backing up, but not for Grex.
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scott
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response 6 of 79:
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Jul 26 21:28 UTC 2000 |
CD-R would be about 1/3 the capacity of our current system, so somebody would
have to hang around and change disks frequently.
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scg
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response 7 of 79:
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Jul 26 21:31 UTC 2000 |
Is there a good reason to do 8-mm rather than DAT at this point?
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scott
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response 8 of 79:
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Jul 26 22:07 UTC 2000 |
We do have a 2nd donated drive to possibly play back old 8mm tapes on. Last
I heard, I'd given it to dang to test out. And I've got a cleaning kit for
the currently installed drive, too.
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steve
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response 9 of 79:
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Jul 26 22:35 UTC 2000 |
First, thanks to Jan for entering this item. I only now managed
to claim time for this...
8mm tapes have some very important advantages that others don't
have, among them ease of manufacture, and longevity of data. Less
than one month ago I had to read an old 8mm tape that I'd created
at a place where I worked long ago--the tape read just fine, no loss
of data whatsoever. It was created in 1988. Others have had good
luck with this kind of longevity, as well.
As the board meeting when I gave the board a 'heads up' about
our meeding a new drive, I got some numbers mixed up, which I
think some others have figured out. I'm sorry for that--I really
need to not dash out the door grabbing the notes at the top most
of the pile... <blush>
The Exabyte unit I was thinking of was the 7G unit, which
compresses to 14G. So far the best price I have found for it is
$1,026 for an internal Eliant 820.
Pricing for 8mm tapes (the 160mXL type) are $7.50 for Maxell,
$10 for Sony, $12.50 for IBM and $13 for Exabyte tapes.
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prp
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response 10 of 79:
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Jul 26 23:11 UTC 2000 |
Why does Grex have to shutdown to do a backup?
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steve
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response 11 of 79:
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Jul 26 23:23 UTC 2000 |
Because when Grex is up, some files are open, and while dump
can indeed operate on an active filesystem, a quiscent one provides
that ALL files will be saved in the correct manner. If it were
just individual user files that could be munged, it might (though
I would disagree with this) be OK to do live dumps, but considering
that systems files need to be backed up too, and having those
incorrectly saved could lead to a real mess, it isn't worth it
to keep the system up during a dump.
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i
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response 12 of 79:
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Jul 26 23:44 UTC 2000 |
How fast can grex back up to /dev/null? There's little advantage in
a tape drive that can write MB's to tape much faster than our hard disk
system can read them off the platters. (If grex is slow here, does a
software upgrade look like a likely fix for the problem?)
From a quick df, it looks like grex has a bit over 8GB of hard disk
capacity to back up right now. Should we be looking for a drive that
will look good backing up 12-18GB of disk?
DDS-3 (4mm DAT, 12/24GB) looks cheaper than the 8mm stuff discussed
here (both drive & media). My slight experience with HP's DDS-3
units hasn't been favorable, though.
Is there some big downside to the 14/28GB drive (jan in #3) vs. the
7/14GB drive (steve in #9) that cost very nearly as much? (Can the
14/28 use cheaper 7/14 media until we need the extra capacity?)
From my experience of a few years ago with their 4mm product, i'd
*STRONGLY* suggest that we avoid Maxell tapes. I don't have very
favorable memories of Sony either.
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steve
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response 13 of 79:
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Jul 27 00:05 UTC 2000 |
The problem with 4mm drives is that the quality varies all over
the place, and replacement of 4mm drives after a year or two is not
at all uncommon. I've seen enough of them lately to not hold them
in high regard. After successfully repairing one, I wasn't very
impressed with its hardware manufacture, either.
Tapes are always an interesting story, and different companies
have better and worse reputations on different media. Scott can
probably correct me if I'm wrong, but for us the Maxell tapes worked
out well, with another brand not being as good.
With regard to speed, the Eliant may be faster than we can
write to it, but that doesn't mean we can't get a faster SCSI
controller on the 4/690, and/or whatever hardware platform we
eventually jump to.
Given that writing a 7G tape in uncompressed mode is about
three times larger than our 2.3G tapes are, even the $13 Exabyte
tapes start looking cheap--I don't think we've paid less than
$5 for any of our current tapes (expcept for the free ones we've
gotten), so $13 a tape is still quite reasonable. I'm betting
that one of the others will be just as good however, but there
will be a certain amount of experimentation here.
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i
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response 14 of 79:
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Jul 27 00:16 UTC 2000 |
I wasn't thinking that the SCSI host & bus bandwidth would limit our
backup throughput (my guess is that the HDs' media transfer rates are
lower anyway); i was thinking of drive mechanics (seek & latency
times) and jillions of small files. Especially with multiple drives,
clever backup software can do a great deal to get around this.
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steve
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response 15 of 79:
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Jul 27 00:20 UTC 2000 |
Heh. Except that "clever" often leads to problems. I prefer
the tried and true dump/restore combunation, which while perhaps
not as sleek as some of today's backup systems, *works*. It also
helps that our restore program has been modified to deal with
some of the strange things that our users do, like creating deeply
nested directories, and insanely long filenames. Marcus has
taught restore to properly deal with the oddities it encounters,
which is well worth it...
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steve
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response 16 of 79:
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Jul 27 00:21 UTC 2000 |
I just found another source for the Eliant; the price is listed
as blow out, and wants an email. I'm doing that now...
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steve
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response 17 of 79:
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Jul 27 00:47 UTC 2000 |
I think techstore.com has Exabyte tapes for $8.09 each. At
that price, I don't think we need think about any of the third
party manufacturers.
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eeyore
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response 18 of 79:
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Jul 27 02:28 UTC 2000 |
Something that STeve mentioned at the meeting, and I haven't seen mentioned
here. Yes, this is expensive....but once we have it up and running, we'd not
need to replace it for years. It will certainly be good for several Grex
upgrades.
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janc
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response 19 of 79:
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Jul 27 02:45 UTC 2000 |
The specs for the Eliant are here:
http://www.exabyte.com/products/8mm/eliant/
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sno
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response 20 of 79:
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Jul 27 03:07 UTC 2000 |
It seems to me that a buffered backup to an unused disk volume would allow
for the minimum of down time on the system. Then raw copy the unused
disk volume to the tape while the system is running. Of course, the
operator would carefully choose the size and order of data preserved
in such a manner including when the buffered volume is actually
placed on a tape.
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janc
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response 21 of 79:
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Jul 27 03:12 UTC 2000 |
THere is a table of which tapes are read by which Exabyte drives at
http://www.exabyte.com/products/media/index.html
The Eliant can read and write
15m, 54m, 112m, and 160mXL
The Mammouth LT can read all of those but not write them.
It can read and write
22mAME, 45mAME, 125mAME
What are our current backup tapes?
160mXL tapes are $8 here:
http://www.techstore.com/ts/spec_info.asp?sku=888EXB675
The AME tapes really do appear to be $40 or so. Though the Mammoth-LT is
twice as fast, and has twice the capacity for almost the same price, the
much higher media cost probably rules it out.
If you go to http://www.ezsystems.com/ and search for "820Si" (not "Eliant"
or "Exabyte" - their search engine really sucks) there is a price of $599
for what appears to be an Eliant drive. This is way out of line with
the other prices I've seen, which are nearer what STeve says, so it may
be a hallucination.
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steve
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response 22 of 79:
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Jul 27 05:02 UTC 2000 |
Our current tapes are 112m; the Eliant will be able to deal
with them for both read and write, not that I ever expect to do anything
other than read such a tape with the new drive.
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albaugh
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response 23 of 79:
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Jul 27 05:08 UTC 2000 |
Do the "modern" tape systems you've got your eye on have drivers that
work under Sun O/S?
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steve
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response 24 of 79:
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Jul 27 05:23 UTC 2000 |
We're verifying that now; they support SunOS, or I should say a
driver in the kernel does. There isn't any specific software that
talks to the drive--dump and restore and others do that, via talking
through the /dev/rstX devices.
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