Tom Goldberg
Forum Replies Created
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While there may be slight differences under the hood, HP actually builds LTO-5 drives for Quantum.
Tom Goldberg
Cache-A Corporation
602 Park Point Drive
Golden, CO 80401
mailto:tom.goldberg@cache-a.com
https://cache-a.com -
Hi Bob,
We are here, busy helping customers. Sometimes I don’t see postings on the Cow as soon as I’d like, especially in this case.
Your field support for Cache-A products is invaluable and I want to do everything possible to keep you happy. As I noted in my personal email to you, I now grovel in public and beg your forgiveness.
Best regards,
TomTom Goldberg
Cache-A Corporation
602 Park Point Drive
Golden, CO 80401
mailto:tom.goldberg@cache-a.com
https://cache-a.com -
We at Cache-A have done a reasonable number of cross-compatibiltiy tests and have kept in close communication with our partners at HP who have also done extensive cross testing.
So far we have not seen any cross platform issues reading other party’s LTFS tapes as long as the underlying driver version is v1.2 or later. Very early on, we saw problems where IBM had changed block sizes as allowed for in the spec but not matched by us and others; that issue has been corrected for a long time now.
Since that time we have had no interchange issues with Cache-A LTFS tapes going to other vendor’s implementations nor with good LTFS tapes from other vendors being read in Cache-A systems.
Note that we have had problems with improperly made tapes – we find tapes that have been ejected before the index was written, tapes with unrepairable file systems, and even tapes that users believed were LTFS but were in fact not. If a tape can be read properly in the v1.2 or later LTFS system that made it, there should be no interchange issues.
Tom Goldberg
Cache-A Corporation
602 Park Point Drive
Golden, CO 80401
mailto:tom.goldberg@cache-a.com
https://cache-a.com -
Ryan,
You will be hearing directly from our support engineer on this shortly. FYI, it is very unlikely that overfilling a tape had any direct cause of this issue.
For the rest of the forum, multiple flashing lights on an HP LTO tape drive almost always indicates some kind of hardware fault. This may be transient and could clear with a reboot or may be something more serious.
One common cause to be suspicious of is cabling – the SAS connector on the back of the drive, and that cable’s power and connection to the SAS card are all always worth checking.
If a restart and a cable reseat doesn’t clear up the problem, such multiple LED flashing probably means a tape drive failure and it will have to be replaced.
Tom Goldberg
Cache-A Corporation
602 Park Point Drive
Golden, CO 80401
mailto:tom.goldberg@cache-a.com
https://cache-a.com -
I believe it is incorrect to call LTO either slow or costly.
At $50 per 1.5 TB tape, the cost is 3.2 cents per gigabyte (LTO-5 tapes can now be found for $40 and will continue downward to about $25 over the next year)
Amazon Glacier storage is 1 cent per gigabyte per month, S3 costs even more, and with both you have to pay additional transaction costs to get your data back.
LTO tapes last 30 years which works out to less than .00001 cents per gigabyte per month. And you don’t have to store them in Iron Mountain, any cool dry place will do. You can even make two copies, store them in separate locations and have the same level of protection as many movie studios for media costs that are less than 6 months of Amazon storage costs.
LTO-5 tape drives can archive data at 140MB/s – that is much faster than even an average 2 disk drive RAID0 and orders of magnitude faster than trying to get your data down some pipe to cloud storage.
There are many reasons to use cloud storage – speed and cost are not among them today
Tom Goldberg
Cache-A Corporation
602 Park Point Drive
Golden, CO 80401
mailto:tom.goldberg@cache-a.com
https://cache-a.com -
I wanted to take the opportunity to advise everyone that Cache-A version 3.0 software fixes this problem.
As Andrew pointed out, we needed a newer version of netatalk and now that v3.0 is based on CentOS 6.2, the newer netatalk is included… along with a whole bunch of performance improvements!
BTW, Bru never had this problem because it runs under the MacOS – we run under Linux and have always played nice with Windows and Linux as well as the MacOS providing a true cross-platform solution.
Tom Goldberg
Cache-A Corporation
602 Park Point Drive
Golden, CO 80401
mailto:tom.goldberg@cache-a.com
https://cache-a.com -
Hi Gerald,
I will defer to the CatDV experts on the advantages of v9.x vs. v8.x and focus on the Cache-A side of your questions.
The reason we say it is a bad idea to modify anything inside the VTAPE is that the VTAPE is a watchfolder. Your Cache-A appliance is constantly monitoring that folder for changes and will archive anything it sees that is new. You move a file – it will get re-archived. You rename something – we see it as new and will archive it again.
Bryson’s comment that LTO doesn’t like a lot of little files is not quite correct – we handle small files fine, what causes problems are lots of little archive sessions. So the easiest way to make CatDV prevent small sessions is to get all your content organized and ready for archiving and select a large data set before you select Send to Archive. If you can run the job with 10 GB or more per session, you will have fewer problems and get better tape utilization.
There is a work-around if you want to manage your content within the VTAPE: First, insert the tape you will be archiving to, the Cache-A will create a VTAPE for that tape. At this time you can check available space, rename the volume, etc. Then eject the tape but select “Keep the VTAPE.” Now you freely move your stuff around manage to your heart’s content, and when you’re all done, re-insert the tape. The Cache-A will tell you that the tape’s contents doesn’t match the VTAPE and gives you the option to Sync the contents – select that button and everything that wasn’t in the VTAPE when you ejected will get added to that tape.
Finally, I’d like to take issue with Bryson’s assertion that “you cannot perform “staging” through the SDK” – you certainly can. Our SDK will allow you to archive content from any folder on any volume it can see, and will allow for lists of files or folders to be archived at once (which is effectively staging). CatDV chose to not use that class of command but rather initiate archiving by moving data to the VTAPE. That said, even though I disagreed with this one point, I want to thank Bryson for being a knowledgeable resource for this community (and an all-around great guy).
Tom Goldberg
Cache-A Corporation
602 Park Point Drive
Golden, CO 80401
mailto:tom.goldberg@cache-a.com
https://cache-a.com -
We recommend a max target of 1425GB per LTO-5 tape to assure room for the TOC, and yes, doing it in fewer sessions is better, although you don’t have to do it all at once.
We are happy to look at your deck and any suspicious tape – please contact our support group as outline on our web site here
Yes, I will be at IBC in our new stand in hall 7 booth 7.E06!
Tom Goldberg
Cache-A Corporation
602 Park Point Drive
Golden, CO 80401
mailto:tom.goldberg@cache-a.com
https://cache-a.com -
Hi Whitney,
I will defer any questions about how CatDV is tracking archiving tapes to those experts, but would like to provide answers about lost space.
Data tape can lose space for a wide variety of reasons:
Dirty heads or poorly performing tape decks as well as network connection issues can cause large amounts of lost space due to the need to re-write data that didn’t get written correctly (LTO does read-verified writes, checking every bit and rewriting it if it didn’t get onto tape perfectly).
Small amounts of lost space such as your 800MB out of hundreds of GB are usually due to less serious issues. Every time you write a single file, the deck must rewind, find the end of data and leave an empty block and markers for the start of new data. Each write session creates a tar package (what we call a tarball) and those tarballs have wrappers that use up a small amount of space as well. Thus the more sessions you have, the more these small losses add up and the more net loss you will see.
If you grab a whole stack of files and archive them together, the less space loss you are likely to see. You might even see a negative space loss (space gained through lossless compression in the deck).
You are welcome to contact our support group and have us evaluate the health of your tape drive if you have concerns about that (as long as you are under warranty).
Tom Goldberg
Cache-A Corporation
602 Park Point Drive
Golden, CO 80401
mailto:tom.goldberg@cache-a.com
https://cache-a.com -
Hi Whitney,
The best way to avoid spanning is to not put too much on a tape. You can turn it off under System Tools page > Settings tab > Multiple Volumes off. However, if you overfill a tape in this case, you end up with a tape that has no TOC – not good either.
In the CatDV “Archive Media Files” dialog there is a line that displays the Current Tape and in parentheses after the Media ID of the tape is a percentage displayed (45.6% used). To be safe, I would tend to move on to another tape once you get above 90%.
Tom Goldberg
Cache-A Corporation
602 Park Point Drive
Golden, CO 80401
mailto:tom.goldberg@cache-a.com
https://cache-a.com