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#1
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What's so great about tape?
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? -- Anton |
#2
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In article , Boll Weevil ruminated:
First of all, nobody makes a robotic hard drive changer. We go through about 500 tapes a day using 20 to 40 tape drives concurrently all managed by automated robotic tape libraries. I can't imagine to trying Let me get this straight. You back up 50 terabytes per day? Or are you using older/smaller capacity technology, let's say DLT1, and backing up, say, 10 terabytes per day? 10 terabytes per day = 3650 terabytes per year. You're saying that your installation is pushing 3650 terabytes of data per year through your systems? Or are you saying that, due to the inefficiencies of current tape backup solutions (which operate upon a whole-file basis rather than on a differential block basis), you need 3650 terabytes of tape storage to store, say, 365 terabytes of changed data? -- 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! =----- |
#3
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On 3 Sep 2003 14:55:07 -0500, Eric Lee Green wrote:
In article , Boll Weevil ruminated: First of all, nobody makes a robotic hard drive changer. We go through about 500 tapes a day using 20 to 40 tape drives concurrently all managed by automated robotic tape libraries. I can't imagine to trying Let me get this straight. You back up 50 terabytes per day? Or are you using older/smaller capacity technology, let's say DLT1, and backing up, say, 10 terabytes per day? 10 terabytes per day = 3650 terabytes per year. You're saying that your installation is pushing 3650 terabytes of data per year through your systems? Or are you saying that, due to the inefficiencies of current tape backup solutions (which operate upon a whole-file basis rather than on a differential block basis), you need 3650 terabytes of tape storage to store, say, 365 terabytes of changed data? 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. We use STK 9840A and 9840B drives. These drives can do about 20GB per tape at about 20 to 40 mb per second. 500 tapes??? Well, I think I've mistaken or I kicked out an old number. We probably use twice that. Most of the SAN disk is used for Oracle and SAS databases. Oh yea, we also have about 200 TB of mainframe but IBM manages that. So, do some math and figure out how many tapes we use on a full backup. You can save me some time. |
#4
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"Boll Weevil" wrote in message
... On 3 Sep 2003 14:55:07 -0500, Eric Lee Green 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. We use STK 9840A and 9840B drives. These drives can do about 20GB per tape at about 20 to 40 mb per second. 500 tapes??? Well, I think I've mistaken or I kicked out an old number. We probably use twice that. Most of the SAN disk is used for Oracle and SAS databases. Oh yea, we also have about 200 TB of mainframe but IBM manages that. So, do some math and figure out how many tapes we use on a full backup. You can save me some time. So you work for Boeing, right? One of the largest Powderhorn sites I know of... Rob |
#5
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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 |
#6
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"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 |
#7
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"Anton Rang" wrote in message
... "Rob Turk" writes: "Marcin Dobrucki" wrote in message ... August 2003 issue of SysAdmin Magazine (www.sysadminmag.com) has an article just for you. "Tapes: A Modern History, Trends", by Henry Newman, p. 43 /Marcin This article is so full of semi-technical nonsense that it ain't funny anymore. I agree with the overall conclusion (tape is here to stay) but this guy has definitely not been doing his homework on helical scan recording. This stuff is directly copied out of 10-year old Quantum DLT sales pitches. Yuck... I'm curious, what do you disagree with in the article? I don't know enough about helical scan vs. linear to make a strong argument one way or the other, but I haven't run into anyone with several hundreds of terabytes stored on helical scan tapes yet. Henry's company (www.instrumental.com) has set up a fair number of multi-petabyte tape sites, so I tend to give them some trust. The section that describes the 'differences' between linear and helical scan is totally out of wack. The claim that 'a small defect on tape would create data corruption in a full buffer' is so blatantly wrong, it's just sad this shows up in such an article. The stuff about tape passes, tape longevity, mechanical stability et all, this is the stuff that linear and helical vendors would throw at each other 15 years ago. None of it is based on facts, especially with most of today's implementations In my opinion, helical scan and linear technology are just two different ways of accomplishing the same goal; create sufficient head-to-tape speed to get the desired transfer rate and control it well enough to allow the desired data density. Neither is better per se, they can both be implemented right and wrong. Rob |
#8
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(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: http://www.bacula.org/ YMMV. -- 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 |
#9
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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. In the situation we're discussing, being able to do just one tape a night is an *advantage*. YMMV. I should say so, why would I want negative milage? -- I've seen things you people can't imagine. Chimneysweeps on fire over the roofs of London. I've watched kite-strings glitter in the sun at Hyde Park Gate. All these things will be lost in time, like chalk-paintings in the rain. `-_-' Time for your nap. | Peter da Silva | Har du kramat din varg, idag? 'U` |
#10
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(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 |
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