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Advise on Tape / Drive to purchase...

 
Nigel Wright_1
Frequent Advisor

Advise on Tape / Drive to purchase...

We have a huge number of tapes of varying types - DLT1 up tp DLTV. It has been decided to recover all the save sets - they are all in VMS backup format - and copy them onto new tapes of a higher capacity. This will place the files onto newer media plus reduce the quantity of tapes, and thus the room to store them all. Can anyone suggest what Tape / Drive combinations we could possibly move to.

Many Thanks in advance Nigel.

12 REPLIES
Hoff
Honored Contributor

Re: Advise on Tape / Drive to purchase...

The LTO (Linear Tape Open) Ultrium series drives are the analogous replacement.

You'll have to define "huge" here, as my definition for that value is almost certainly different than yours. Huge (to me) is a room of XP-class disk arrays and ESL-class LTO-4 libraries stuffed with drives and cartridges, and with an off-line store for the spill-over. (Oh, and on-site field servants that should get issued Segways. :-) )

You'll also have to define how many of these cartridges need be off-line or near-line, and around how much manual intervention from an operator is expected and permissible, and around how many tape accesses might occur in parallel, as these factors will (in aggregate) point to an individual LTO drive or to an LTO library, and to the eventual capacity of the LTO library.

One caveat: make sure there is a degree of longevity and availability around whatever archival storage you choose. I'm aware of some folks that picked what are now comparatively rare MO libraries and MO drives, and they're locked into some difficult gear and difficult software.

There are folks around that can help you navigate the available gear and for your particular requirements more specifically. Resellers can certainly be useful here, too.

Stephen Hoffman
HoffmanLabs LLC
Jon Pinkley
Honored Contributor

Re: Advise on Tape / Drive to purchase...

If you are going to the expense of migrating your tape data, the cost of the drive is going to be a relatively small portion of the total cost.

The LTO family is what I would recommend, as it is not tied to a specific vendor and has a large market share; therefore it is likely to be around for a while.

I wouldn't consider anything less than LTO-3, and would strongly favor LTO-4 and a model that has the hardware data encryption ability built in, whether you plan to use it or not.

Another thing to consider is the format of the data. If the data is related to VMS, I would leave it in VMS Backup format, as that has a good track record of being supported for a long period of time. It also preserves the VMS file attributes. If you are never going to use the data on a non-VMS system, the ability to read the data there isn't a compelling argument to use a different format. And in the future, you should still be able to read the data using VMS on an emulated machine.

You are going to migrate the data to new media. If you have ever thought of the possibility of encrypting your backup data, that would be the time to encrypt it.

VMS BACKUP currently does not have built in support to control LTO-4 encryption. However, I believe a code example to turn the encryption of an LTO-4 drive was posted here in the VMS forum.

Note that if you do encrypt your data, you need to be very diligent in preserving the encryption key, as without the key, the data will be essentially worthless given current technology. In other words, deciding to encrypt your data should be something that has some thought and planning done before the decision is made, and well tested before the migration of the data is started.

Jon
it depends
Nigel Wright_1
Frequent Advisor

Re: Advise on Tape / Drive to purchase...

Thanks for the advice so far:-

We have in storage about 46TB on DLT3, DLT4, RV20s.

We access these, to restore files, about once every 2 weeks. They are all in VMS backup format.

Thanks again Nigel.

Robert Atkinson
Respected Contributor

Re: Advise on Tape / Drive to purchase...

Agree with Hoff and Jon - LTO is the way to go.

We've been running 2 LTO3 libraries for >12 months now, and have had very few problems, so unlike some of the older drives, seem to be more stable (I'm sure there's someone that would disagree with that statement, though).

I'd be wary of going to LTO4 just at the moment, purely based on the cost.

We can currently get LTO3 at around £30 each, but LTO4 comes in at a wapping £80. This will come down very fast, but being ahead of the market means you'll be paying a lot of money for your media.

It perhaps better to buy an LTO4 capable drive, but transfer your old backups onto LTO3 until the price drops.

Rob.
Jon Pinkley
Honored Contributor

Re: Advise on Tape / Drive to purchase...

The LTO-4 can read/write LTO-3 media, but can't create encrypted LTO-3 data (using the drives encryption capability). So if you don't need encryption, and cost is more important than space, then you can certainly use LTO-3 media.

If this is for archival use, and you never intend to overwrite the tapes, and want to prevent accidental erasure of the data, Write Once media is available, but I have never used it and wouldn't be surprised if it cost more. I don't think it is safe from a high power degausser, you just won't be able to write to the tape before the "high water mark" (that probably isn't' the term they use). I don't even know if special knowledge of the write once capability is required in the operating system, i.e. I don't know if VMS would see Write once media as write locked if you loaded it a second time.

Does anyone know how VMS reacts to WO media?

Also, I have no idea how you were going to copy the old data to the new media. You almost certainly don't want to copy tape to tape, as the output drive would be starved, and it would have to go into shoeshine mode.

So you will probably want copy the data to disk, and from disk to tape. In general you won't be able to use copy if any of your savesets have blocksizes greater that 32256.

Also copy does no saveset integrity checking, however since everything you have is on DLT, you are very likely to either get correct data, or a parity error, with very little chance of recovery past that point.

If it is ok to change the headers of the savesets, the most reliable way is to use backup to restore to disk, then backup to new savesets. However, that could be slow if the saveset have many small files. There is also Save Set Manager, but I don't know how up to date that is, i.e. I am not sure it has been updated since the latest changes to backup, and I have less faith in SSM than backup, primarily because backup gets much more use.

Jon
it depends
Nigel Wright_1
Frequent Advisor

Re: Advise on Tape / Drive to purchase...

Thanks again for the replies so far.

We won't be going for any sort of encryption.

We have a lot of experience with SSM, which has worked perfectly on all the ones we done so far.

Say we went for a standalone LTO3 capable drive, any ideas what we go for?

We are still on VMS version 6.2 on our main boot node that has direct access to the storage, it is not possible to upgrade this machine, so I am thinking of adding another alpha to cluster at the min version of VMS to support the new drive, and give it direct access to the main storage. This would effectively be our backup server.

Any thoughts, suggestions would be much appreciated.

Robert Atkinson
Respected Contributor

Re: Advise on Tape / Drive to purchase...

This is basically what you're looking for, either desktop or rackmount :-

http://h71028.www7.hp.com/ERC/downloads/5983-0148EN.pdf

Rob.
Robert Atkinson
Respected Contributor

Re: Advise on Tape / Drive to purchase...

Jon Pinkley
Honored Contributor

Re: Advise on Tape / Drive to purchase...

What is the highest capacity DLT drive you have? Is it a DLT8000 based drive (40/80)? If so, you probably have a wide LVD SCSI adapter on your system.

I know we can connect an LTO-3 (Ultrium 960) to the same type of SCSI adapter that we use with the DLT8000. I doubt any LTO drive is supported on VMS 6.2, since I don't think LTO is 10 years old yet. That doesn't mean it won't work. But I can't remember if 6.2 supported fast skip, even with MKSET. If you have hundreds of savesets on one LTO-3 tape, you will almost certainly want to use fast skip.

Since you have 6.2, do you have anything that matches sys$etc:mkset.* ?

Of course if you have a machine that supports 6.2, it may be hard pressed to be able to feed an LTO-3 fast enough to keep it streaming, even in its "slow" mode.

If you can get a loaner LTO-3 drive to see if it works with VMS 6.2, that is what I would do first.

What kind of disk storage do you have that will be shared with the backup server? Even that may be a limiting factor is your ability to supply data to the tapes quickly enough.

In general, I don't like mixed version clusters. They add a lot of complexity and you must conditionalize the use of any new features in command procedures, so the new features will only be used on new versions, etc. And there are the support issues as well. In my opinion, using an unsupported tape drive on an old version of VMS has lower risk than mixing widely different versions of VMS in the same cluster.

This is the second thread this week mentioning a 6.2 system that can't be upgraded.

http://forums11.itrc.hp.com/service/forums/questionanswer.do?threadId=1193901

Good luck,

Jon
it depends
Nigel Wright_1
Frequent Advisor

Re: Advise on Tape / Drive to purchase...

Thanks Jon et al for all the info so far.

We have 3 TZ89 desktops which are conneted to an Alpha 2100A running 6.2, we have a number of other members all running 6.2, except for an DS10 on 7.1-2.

The main storage is a HP SA 7000, mostly fully populated, in a single controller configuration.

Nigel Wright_1
Frequent Advisor

Re: Advise on Tape / Drive to purchase...

Correction should be RA

Thanks Nigel.
Hoff
Honored Contributor

Re: Advise on Tape / Drive to purchase...

Right off the cuff, you probably won't want the following approach, but I'll include it to help you scale your requirements, and there might well be a reason here to look to use this approach for your backups...

Disk spindles are terabyte-scale now, so we're well below the capacity of a typical disk rack. HP is offering 500 GB spindles in some configurations, and TB disks are in common use.

Biggest issue with on-line storage is connectivity (getting the bits from the host to the platters), and a NAS drive array with FTP capabilities might well get you what you need here. One of the HP AiO boxes, for instance, or various similar products. (The controller and cabinetry is now usually the largest part of the price, not the storage.)

This (US$275 current street price per bare terabyte spindle, and US$110 per half-terabyte spindle) is probably more than you want to spend if you're looking at an LTO-3 (older) drive, and thus this reply is intended solely to allow you to "scale" this archival requirement with what passes for current-generation storage.

FWIW.