If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#21
|
|||
|
|||
(Peter da Silva) writes:
Amanda does too. Really? Last time I looked it didn't. I'll have to update my knowledge. In the situation we're discussing, being able to do just one tape a night is an *advantage*. [...] ACK. Misunderstood what was being said. -- David Magda dmagda at ee.ryerson.ca, http://www.magda.ca/ Because the innovator has for enemies all those who have done well under the old conditions, and lukewarm defenders in those who may do well under the new. -- Niccolo Machiavelli, _The Prince_, Chapter VI |
#22
|
|||
|
|||
"Dan Foster" wrote in message
... In article , Boll Weevil wrote: See if you can add this up. To start, we have about 200 Sun servers and about 1200 NT servers. About 100 Sun servers and about 100 NT servers are on the SAN and share the following EMC and Hitachi subsystems: 7 EMC 8830 frames with about 13 TB raid 10 useable, each 1 Hitachi 9980V frame with about 45 TB raid 5 useable There are a whole lot of direct attached SCSI disk arrays and internal disks in each of the 1200 NT servers. I can't even start as to how much storage these servers account for. These all get backed up. Rough calculations shows that using hardware compression for a LTO-2 setup, one could do all of the above in about 2 (or so) fully decked out IBM 3584 LTO libraries (just as an example), assuming an average size of directly attached storage for each of the NT servers being 1 TB. A decked-out LTO-2 library with 6 frames should yield in the neighborhood of about 720 TB of tape storage capabilities. If 1200 servers * 1 TB = 1200 TB; that'd be one decked out LTO library and a second library with about 240 TB of available tape space. For the other stuff... 13 * 7 = 91 plus 45 TB = 136 TB. So you'd still have 104 TB of free data space, and capable of doing a single full backup for everything with two libraries and about 3500 tapes. This assumes 400 GB (hw compressed) LTO-2 tapes; if you are using 20 GB tapes in uncompressed mode, then your tape requirements goes up by 20 times 3500 for at least 70,000 tapes. Also, if the average per-NT server for storage is other than 1 TB, that would also influence number of tapes required, as well. -Dan Capacity-wise you're probably correct, I didn't do the math. However, many of these types of setups have a different limiting factor, being the number of changes per hour that a tape robot can handle or the number of drives available. You'd need enough drives to keep the robot busy and a fast enough robot to keep the drives going. This all depends on the access pattern. If such a system is used for record based archives then you'll usually need a lot more exchanges per hour than in a pure backup environment. The fastest Powderhorns do about 450 exchanges per hour. Just inserting a separate cartridge for each of the 1400 systems takes 3 hours, assuming one robot and unlimited drives. Cascading robots help bring this to a lower number. Also, with this many systems, even if you are doing backup only, you will run into the issue if the number of parallel tasks you can run. You need a large number of drives in order to give each system a chance to access one, or you need to revert to backup software that can combine (multiplex) several data streams into one. To make a long story short, capacity is only one factor of many when dealing with a setup as large as this. Rob |
#23
|
|||
|
|||
"Paul Rubin" wrote in message
... "Rob Turk" writes: For Exabyte drives, for 8200's no mods were needed. The firmware (32KB of code on an 8051 CPU) did not require any changes to space to the next filemark after EOD. Not enought smarts to detect EOD while spacing ;-) For all other 85xx drives a standard EE-image implementing 'directory support' allowed you to do the same thing. No tricks, no switching power, just using the features of the drive. Thanks, that helps. How is the situation for current Exabyte/Ecrix drives? Also, suppose you have an M3 or VXA2 cartridge and cut the tape somewhere in the middle with a scissors. Can you get back (most of) the data from both pieces without having to go too crazy with special programming? Is there enough redundancy to not lose data around where the cut is? I figure you can't splice the tape, but maybe you can spool each piece onto another cartridge or something. If you cause physical damage to the media, you will need to resort to rigged decks and specialised recovery techniques to get the data back. Just like you would have to if you open up your harddisk and scratch the platters. That level of recovery isn't part of standard functionality in any consumer product. With the VXA-2 packetised data format, the chances of getting everything back is pretty good, if the cut is clean. Physically the blocks that are cut through are beyond repair, but the logical format allows for a lot of missing blocks through multiple levels of ECC correction. Due to the way data is written, tape deformation is also not an issue. With most other tape technologies (including M2) you will likely lose the data blocks/tracks that are physically damaged, but everything before or after should be recoverable. Just not on a consumer deck ;-) Rob |
#24
|
|||
|
|||
In article , Anton Rang ruminated:
Eric Lee Green writes: In article , Malcolm Weir ruminated: Tape's failure modes tend to be less catastrophic than disk's. E.g. That is not my experience. In general, when a section of tape becomes unreadable, every bit of tape after that section is no longer accessible. I've never seen a drive which behaved that way. Are you sure it's not the driver on your system refusing to skip past the bad block? Could very well be. I haven't had bad tapes in a long time. The last time was back when I was doing SCO Unix, which was seriously broken in a number of other ways too. -- Eric Lee Green Linux/Unix Software Engineer seeks employment see http://badtux.org for resume -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
#25
|
|||
|
|||
In article , Peter da Silva ruminated:
In article , David Magda wrote: (Peter da Silva) writes: [...] With Amanda it's always one tape per drive per night, so there's no other messing around necessary. Bacula supposedly allows for multi-volume backups: Amanda does too. Amanda has one serious deficiency, built into its basic architectu It cannot back up any file larger than a single tape. So if your tapes hold 35gb, it cannot back up a file larger than 35gb. Granted, that's not a *huge* deficiency in today's day and age, with huge tapes (by comparison with the old days), but in some environments it still *is* an issue. One environment that I did consulting work on generated a 300gb flat file that needed to be backed up every night. That required some interesting end-of-tape handling using free tools (a commercial tool would, of course, have no problem at all, since commercial backup programs have been doing tape spanning for decades). -- Eric Lee Green Linux/Unix Software Engineer seeks employment see http://badtux.org for resume -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Cannot eject tape from PV 120T DLT1 Autoloader drive | [email protected] | Dell Computers | 3 | January 25th 05 08:56 PM |
Great storage method, is it available in UK??? | Mark | General | 5 | March 14th 04 10:58 AM |
ati video on demand is great - export sucks | Nicholas Tse | Ati Videocards | 1 | August 28th 03 05:11 PM |
cutting psu wires | Pen | General | 4 | July 27th 03 07:49 PM |
Records great, but what about the audio??? | mxh | Ati Videocards | 7 | July 22nd 03 05:37 AM |