SDLT reliability

[Steve Reece_3]

A mate of mine has a number of clients with HP SDLT tape drives, both 110/220 and 320 GB varieties. Whilst they had no problems with DLT, the SDLT drives have given them no end of problems.
One of his clients has had their drive replaced four or five times, along with media replaced by HP because of tape-edge damage.

Has anybody else had less than optimal performance out of their SDLT drives?

(The drive that the customer who's suffered so many replacements is at the current firmware version and is suffering parity errors on new, HP-supplied, Quantum tapes.)

Thanks in advance

Steve

[matthew robey]

Steve,

yep, I've had to have an SDLT drive replaced 5 or six times.

Hp have blamed the tapes, however it is always the same drive that need replacing (I have 4),
and different tapes have been used.

The backup will run ok and then after a variable ammount of time (ie not always at the same point) the backup will fail.

Matt

[Peter Quodling]

Saw some problem with SDLT's at one site a while back, however have been having issues with LTO's at recent site. It's all flakey and just a matter of knowing how to escalate with the Service folk.

Peter Q

[John Abbott_2]

Just to keep a balanced view... we have 10 320sdlt drives and have used Maxell, Quantum (mostly), Fuji & Sony type I tapes.

We've had no drive swap outs yet and have had about half of the drives since they became available (so a mixture of Compaq and HP badges).

About 6 of the 10 units are used daily.

I think the MTBF for SDLT media is the same as DLT.

Do you use a cleaning tape on the drives regularly? I've been told only to clean them when asked.

Kind Regards
John.

[Jeffrey Willemsen]

It may well have to do something with some batches or manufacturers of the tape cartridges. I see a few drives every month that are brought in with afore mentioned problems (and diagnostics reports tape edge damage) while the drives work perfectly without problems when using another tape cartridge. SDLT itself seems reliable, some cartridges that were acting up did well again after degaussing them.

[DICTU OpenVMS]

At my current site it depends. Once in a while a drive needs to be replaced. After that it runs fine for a very long time. We have about 8 MSL's with about 20 drive's. Most of them are used daily. We have set the MSL to autoclean and reserved 1 slot for the cleaning tape...

[Robert Atkinson]

We have 2 SDLT libraries and 2 internal standalone drives.

In general, they've been better than previous drives (DLT III, DLTIV) but still do require the ocassional swap out or jammed tape.

Robert.

[Steve Reece_3]

As Matthew commented, the drives seem to work for a variable amount of time and HP are apparently saying that the fault is either with the media or with the drive.

For the client that's had four or five drives, no problems with the SCSI bus or the adapter are indicated. The client has had a brand new Quantum tape that has failed, the tape being replaced after the previous one suffered tape edge damage.

[Peter Quodling]

Personally, my favourite tape devices are STK 9840/9940's but now that Sun Microsystems have bought storagetek - who knows.

A quote from a former colleague who worked in DEC tape engineering (TK70 etc) will always stick in my mind. He was asked at a DECUS what he thought of exabyte drives. Without blinking, he responded... "They are great for backups.... But terrible for restores...." Nuff said...

q

[Aaron Lewis_1]

Steve, we had been having a lot of difficulty with some of our SDLT drives. They were constantlly logging errors, around 50 errors on every backup(140GB.)About once a month one of them would fail, we even had one that needed to be replaced 3 times in a week! Our FE decided to replace the SCSI controller as well, even though there were no indications of any errors on the controller. Since then we have gone about 5 weeks without any issues, well tape issues anyway. We still throw a few errors with every backup, but now it's only 2 or 3 a night. The next SDLT we have that fails, I'm going to request a new controller too.

[Steve Reece_3]

That's useful Aaron. Something that I'd thought about but having been told that the errors were either due to the media or the drive, my mate discounted that.
Thanks!

[Cass Witkowski]

There was an article about getting parity errors during backups or even backup hanging if the WSQUOTA and or WSEXTENT was too small.

[Teengh Hergh]

We have 16 110/220 Drives and we are facing the same problem. We have been working with HP since November 2004. HP had replace all the drives, but the errors are still there. HP 2ndary FE think we have worn out cartridges even though the cartridges were less than 2 years old and they are used less than they advertised.

We recently ran Tape Edge Damage test for the new drives and 5 of the 16 replaced drives were failed.

Not sure where to go from here.

[Steve Reece_3]

Sorry that you seem to be getting the same problems Teengh. HP first and second line support are telling us that it's a media issue. How that helps when a brand new, HP supplied tape fails I'm not sure!

[Jeffrey Willemsen]

With regard to the tape edge damage test: if it fails it does not mean the drive failed, the cartridge you tested with is at fault. Replace that one. The message was not entirely clear about that.

[Wim Van den Wyngaert]

Have a MSL that is running for almost 3 years. No problems until now.

But I lost count of how many drive/controller replacements we have had for the DLT891.

Wim

[Harry Su]

We also got endless troubles with HP SDLT tape drive. We bought two servers at the same time, one with DLT and another with SDLT. For two years we had no issues in that DLT drive, however, 3 replacements had been done to the SDLT tape drive (thanks to maintenance contract) and we did not see any improvements. We are still continuously having tape damage problem for every one or two month. I personally gave up calling HP for the replacement again. I believe it is a design problem and is impossible to resolve by changing tape device. Maybe it is the better way to change SDLT to another tape device.

[Jaclyn Rothe]

The issue with SDLT drives is that the tapes are very sensitive to tape-edge damage. Shipping, and incorrect handling can cause TED.
Tapes with TED can bring down SDLT drives.
I recommend DLT drivs or LTO drives.

[Jaclyn Rothe]

The best advice at stopping the endless circle of TED is to replace the tapes and the drive. The problem is if a tape with TED is inserted in a drive, it will cause drive issues. If you run the TED test with no tape in the drive it will deterine if the drive has tape edge damage. LTT will compile a log of tapes with TED, however it is not easy to determine which of these tapes correspond to with ID number.
If you run the TED test on the tape and it passes with no TED damage, then the tape should be fine, set it aside and try the next tape, and so on. Set aside the tapes that are reported as having TED, and dispose of them.

[Steve Reece_3]

Thanks Jaclyn. That makes sense.

[Kari Uusimäki]

Hello All,

There are a few things to remember when dealing with tape drives and keeping up the reliability of backups and restores.

Do use cleaning tapes every time the drive asks for it. The more you use new tapes, the more residue will be emitted from them on the read/write head. More used tapes emit less residue. You can run a cleaning several times consecutively if needed. Do _never ever_ overuse the cleaning cartridges!

Handle tapes as specified (=carefully). Don't forget to do "retensioning" regularly.

Update drive (and library) firmware when new versions become available. Firmware updates do correct problems and makes drives more reliable. They are not made just for fun. One tool you can use yourself for firmware updates is HP LTT. If unsure, do call HP support for assistance.

Some DLT or SDLT tapes might have quality problems. I've seen that also.

When keeping drives in good shape, there won't be much problems and tapes last longer, too. I don't mean that somebody neglects necessary servicing of his drives, but what I want to point out is, that servicing them is very important, because newer drives have very tight tolerances and a lot smaller deviations can cause problems where they weren't seen before with earlier drives. The data density on the tape has grown enormously since when DLT technique was introduced back in '85. At that time you could write 95MB of data on a tape. The newest SDLT tape will hold 600GB of data (over 6000 times more) and the tape is roughly the same. No wonder it is important to care for the drives so they can accomplish their task.

The same discussion goes for LTO drives and tapes. They are similar to DLT and SDLT drives in many ways, even though LTO technique is only a few years old.

With over 15 years of experience with tape drives, I would say that DLT, SDLT and LTO drives are quite reliable.

Good luck with your backups and even more with the inevitable restores!

Kari

[Dan Rolsma]

YES! SDLT has been horrible. SDLT220 was worse than SDLT320. I bought an MSL5026SL, which was replaced once, and then again with a MSL5026S2 all under warranty. Once the budget allowed, WE THREW IT AWAY (went to auction actually)! Tape drives, I forget how many we went through, 8, a dozen. I lost count. At one point HP hardware support told us a 20% tape failure rate is normal (!). I didn't accept that. That is our backup system! Good thing our servers were more reliable. Not a comfortable position to be in. Out of 2500 DLT tapes, we had 2 failures.

We replaced the HP (Overland Data was printed inside on all the circuit boards) with a StorageTek L80, which is 80 percent better. We still go through tape heads, but the library itself is more reliable. The tape heads also work, or they don't, which was a refreshing change. Under HP, sometimes yes, sometimes no. Wait a day and see. Was it the tape? The drive? The SCSI card? Oh, another firmware update, I see. We were always chasing our tails with intermittent problems.

We recently discovered how to put the leader back into the sdlt drives so we don't need to wait for an overnight replacement. We put the leader back in in 10 minutes, once or twice a month. We got a bad batch of tapes not packaged properly and were damaged in shipment, internal damage so I can't tell until the tape causes the tape drive leader to pull out. I tried to work with the vendor to get the tapes packaged properly but had to change vendors.

I just ordered an L80 with HP LTO-3 drives. If they work out, no more sdlt. We could replace all the sdlt drives with LTO drives - because we bought the L80 which is upgradeable. It can even run sdlt and lto at the same time in the same library. Not so with an HP library. Having each available is great for transferring what can be read from the sdlt onto LTO - without buying an entirely new library.

Dan.

[Dan Rolsma]

Steve,

To add to my last post, I verify our tape backups - which causes twice the wear of course, but that is when I've found many problems. I presume that most sites, which do not recheck tapes periodically, or don't notice a tape only filled up part way, may think there is no problem. They just rely on the backup software to signal a problem - and some day they may have a rude awakening when they try to restore an entire system from a particular date.

Dan.