For those using DLT under Windows 2000.
Please check on the KB Article: Q319313 You May Receive a "Tape Drive
Requires Cleaning" Error Message When You Try to Back Up.
Bye
Ernie
-----Original Message-----
From: Mark Bradshaw (BTOpenWorld) [mailto:notthehoople AT BTOPENWORLD DOT COM]
Sent: Thursday, February 27, 2003 10:44 PM
To: NETWORKER AT LISTMAIL.TEMPLE DOT EDU
Subject: Re: [Networker] Drive cleaning
I'd add an additional disadvantage to the library-controlled cleaning. As I
understand it the cleaning light of a drive goes on when a certain error
threshold is breached. I've seen several situations with DLT drives where a
long backup or recovery has been ruined by a drive reaching its need to be
cleaned mid-way through the backup. This was has been most noticeable with
Exchange backups where I've watched the performance drop from 8-9 MB/sec for
a backup down to 1MB/sec for a backup. There have been some situations with
recoveries when I've had to kill the recovery, clean the drive, then kick
off the recovery again (using the same drive) to achieve a decent
throughput.
I even got to the stage of always cleaning a drive prior to kicking off an
Exchange recovery as the library-controlled cleaning just wasn't proactive
enough.
After the problems I had with Exchange I changed to using Legato managed
cleaning and problems of this sort went away :-)
Perhaps now with LTO this wouldn't be so much of a problem....
As far as Legato recommendations go about cleaning I'm not sure, but I've
been recommended by StorageTek support engineers to always use
software-controlled cleaning in smaller libraries (L20 - L700) to avoid the
types of problems described above.
> I'd like to revisit the age old discussion about the best way to do drive
> cleaning. I'm working at a site with a large number of tape libraries of
> various sizes, mainly from StorageTek, but also some older ADIC units. The
> drives are DLT7000 gradually migrating to LTO. They currently use
NetWorker
> cleaning on most of these and we are trying to establish the best
strategy.
> Here is my attempt to be objective about the pros and cons of the two
> possible approaches, as well as my own opinion. I would be very interested
> to hear what the NetWorker community think about this emotive issue. Some
> views from Legato staff would also be welcome.
>
> NetWorker controlled cleaning.
> NetWorker is configured to clean drives at set intervals of elapsed time.
> The cleaning tape(s) is/are stored in a designated tape slot within the
> range normally used for data tapes. The number of cleaning tape uses is
> configured within NetWorker. When a cleaning tape is used up, a
> notification can be sent from NetWorker.
>
> Library firmware controlled cleaning.
> The library firmware is configured to clean drives on demand. The DLT or
> LTO drives are sophisticated enough to send a signal to the library when
> cleaning is needed, and the library automatically loads and unloads the
> cleaning tape at exactly this time. The cleaning tape(s) is/are stored in
> dedicated cleaning slots (library dependent). The number of cleaning tape
> uses is configured in the library firmware. When a cleaning tape is used
> up, most libraries withdraw the tape to the CAP and display a message on
> the library front panel, this may be accessible remotely if the library
has
> remote management software and a network connection.
>
> What is wrong with NetWorker controlled cleaning?
> * The cleaning is based on an elapsed time since the last clean, e.g. two
> weeks. This takes no account of the drive usage in this time, a heavily
> used storage node drive may have had perhaps 168 hours of use in that
time,
> whereas a drive attached to an application server may have only had
perhaps
> 14 hours use. It is highly likely that the former case would have required
> a clean before that time, but unlikely that the latter case is anywhere
> near to needing a clean.
>
> * Cleaning a drive before it is required is wasteful of cleaning tapes and
> can be bad for the drive. DLT drives need infrequent cleaning, LTO drives
> rarely need cleaning at all.
>
> * A heavily used drive may require cleaning before the cleaning interval
is
> reached. It will not get cleaned on demand, and may cause errors or damage
> to data tapes. You can clean manually if there are errors but this is not
> ideal on a remote site because unless you can actually see the library you
> don't know whether the error was caused by the need to clean or some other
> problem.
>
> * One or more data slots are lost due to the need to store cleaning tapes.
>
> * Because cleaning tapes are in data slots, you must take care to specify
a
> slot range to avoid the cleaning tapes when inventorying the jukebox.
>
> What is wrong with library controlled cleaning?
> * NetWorker may show an error on loading a tape when the library is
> cleaning a drive. Usually these errors are recoverable without user
> intervention.
>
> * Cleaning tape usage data is only available from the library front panel.
> Some libraries have remote monitoring software available, but this
requires
> a network connection which may not have been set up. Even with remote
> monitoring software, it requires pro-activity, to go and check usage
rather
> than being automatically alerted.
>
> * When a drive goes bad, it may repeatedly request cleaning and use up a
> cleaning tape. NetWorker cleaning would just show errors. Which is worse?
>
> * Not all libraries support this feature.
>
> Legato Support always recommended using library firmware cleaning where
> available in pre 6.x days. Now it seems that they are recommending
> NetWorker cleaning instead. I don't understand the reason for this U-turn,
> since all the disadvantages listed above still apply. I firmly believe
that
> library firmware cleaning is superior to NetWorker cleaning.
>
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