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How many tpaes does it take to do a GFS?

Posted on 2010-11-17
Medium Priority
Last Modified: 2013-11-14
This GFS Strategy is bugging me as there is no defintive answer to how many tapes to buy. So how many does it take to get to the center of a tootsie pop? So many different numbers for a GFS Routine it is nuts. I have read anywhere from 12 to 19 and neither adds up. Considering that GFS has been around since my Grandfather, one would think someone would have a number of tapes. Now I have to convince my supervisor that hey we need X=Number of LTO-4 Tapes * 2 at the cost of $30.00 a cartridge. The rub is you can't overwrite tapes each day or you don't have a backup to go back to. So what do you tell your supervisor?

O.K. when it comes to backup's I am a belt and suspenders type of guy. Screw incremental and the partials. I want a full backup of my users data every night. Here is my GFS rotation

Monday - Thursday = Son = 4 tapes. I would like to keep the Son a full daily set until the Father is run on Friday = 1 x rotating back after 26 days days. On the 1st Saturday of the month I run Grandpa and want to keep these tapes for a year. 12 tapes. Sunday I run other maintenance programs, do scans and on the 7th day the tape backup rests. My library can hold 28 tapes plus a cleaning tape. I know 29 is an odd number but add a mail slot and you get 30.

In order to do a complete backup of user data takes 2 LTO-4 tapes. So mmultiply by 2. It would be favorable to have an extra 4 daily tapes so 4 tapes don't get run into the ground.

So I need 24 tapes for the Granfather = rotate out every month to keep off-site. 8 Tapes for the Father 6 can't be touched for 4 weeks and 8 tapes for the son. But these tapes can't be touched for 5 days. So I have to rotate in 2 new tapes for the grandfatehr each month. My library holds 31 tapes. So I would have 8 tapes tied up for 6 days, 14 tapes tied up for 28 days  which = 20 tapes in limbo givining me 11 tapes to have on ready for each full backup and to keep any tapes from over use. Golly I hope we don't nee to have 3 tape backups.

Bear in mind I want full backups for as long as I can get my users data backed up. I am open to any suggetions, changes - except full backups, ideas or a better way. Although, we already bought into this system so don't tantilize me with SANS and constatnt backup.

Thank you,
Question by:MarkIsrael
LVL 18

Accepted Solution

BigSchmuh earned 1000 total points
ID: 34162946
Assuming a full backup on 2x LTO-4 tapes is about 1.5TB to backup (4 hours @ 110MB/s), my solution would be to keep most of those backups online on disk...and broke the tapes.
1/ One week of full backups online
You need a minimum of one week of compressed backup space + 1 uncompressed backup space
-Using a large parity RAID array with Enterprise class SATA drives will fulfill this storage space needs
-Verified and compressed (with CRC) full backup to local disks / Every day

2a/ Online storage for long term storage is still way too expensive
I would consider keeping : 10 monthly + 10 weekly = 20 full backups allowing to recover on 1 year period; this is 20x 1.5TB = 30TB in your case !
-Using an online storage would fulfill this storage space needs but requires an expensive 25Mbps line to push 1.5TB per week. I hope that buying some fibers between two sites will allow for a less expensive solution...
-Push the new weekly backup every week

2b/ Offsite tape storage for long term storage
You need some tapes in that case:
-4 locally to handle the copy of your weekly backup
-40 stored offsite to handle the 10 monthly and 10 weekly long term storage
LVL 21

Assisted Solution

SelfGovern earned 1000 total points
ID: 34163394
You're pretty much on track.  One thing to consider is rotating your expired weekly and monthly tapes back in as daily tapes to spread the wear around.

Check your backup application to see if it has help in implementing the GFS algorithm.

Consider full + differential, instead of all fulls; this will decrease the number of tapes you need, but needs no more than a full + one differential for a restore.

Although you've "bought in to this solution", it's possible that purchasing a D2D backup system appliance with deduplication could make your life a lot easier; your daily backups go to disk; because of deduplication you get to store a whole lot in not too much space, and you'd still put your weekly and monthly and archive backups on physical tape.   HP makes a good one -- hp.com/go/d2d -- as does Data Domain and others.   But really, the three big benefits of these things are 1) Backup many systems in parallel, optimizing your backup window and eliminating concerns about slow source systems; 2) quick single-file and other partial restores; and, 3) ability to replicate offsite with a low-bandwidth link.  If you don't fit that use model, they don't make sense.

Don't forget that LTO-4 (and 5) have native HW encryption; if you have any kind of financial or medical data (social security or credit card numbers; bank or investment info; patient info), you probably need to encrypt your tapes; most backup applications will generate and manage keys -- just BE SURE you back up your keys through a different process than you back up the rest of your data.  Save the keys to archival quality CD media or flash drives, with multiple target devices.

Expert Comment

ID: 34244113
Quite a conservative way of backing up your data. That GFS method, which is actually not the real GFS, is what I would call a combination of backup and archive.
But the realy bad thing is, that it looks like there is no attention whatsoever for restore times. Which is what all backup is for, right?
Given the fact that most restores are file restore for files that were created (and got lost) in the last 48 hours, incremental backups or differential backups compris only a small amount of tape. The recovery of data form a recently changed file from a tape with only a few percentage of the tape occupied will deliver a much faster recovery period.
I hope you backup and recovery objectives do not tell you, that recovery of lost data must be fast, otherwise your full backup point of view may work against you in case of real (CEO driven) emergency...

BTW D2D2T backup will also present you a much tighter maze of unrecoverability, since you will perform backup maybe each hour in stead of each day. What if your important data, that was created only 30 minutes after your last backup was destroyed two hours ago?
A simple iSCSI box for the price of a set of LTO tapes must be worthe it, considering the fact that you will then only need a fraction of the amount of tape for off-site tape backup!

Tell you boss you have change for a 100 dollar bill, but only in notes larger than 90 dollar!

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Author Comment

ID: 34248131
I really appreciate all the comments. The D2D2T with De duplication is the way to go but I am stuck with what I have at present. All I backup are my user files and a few choice files from DHCP and SQL.

I have found backing up the OS is, how the French say, "a waste of time". One item is some OS files will not be backed up and the other is, I load the OS just to get my drivers for the tape drive and library. I have seen the bare bones approach but if i don't have all the OS files I am screwed.

I have a nice library with an HP LTO 4 drive using Bar Codes. With Symantec Backup Exec 12.5, soon to be 2010.  I run a SATA RAID 5 with a 256 stripe so that is my backup. Then I have a SATA RAID 1 for my OS.

I prefer the nightly full backup and rotating monthly off site and weekly to a fire safe on site. The LTO-4 runs fast enough to allow this to happen. I don't run a Sunday backup due to othe automated maintence functions. Using the diferential is OK but if I can get the full back up what the hey.

Still trying to nail down the number of tapes is a pain. So far I have come up with 48 as a minimum. We have a lot of GIS files which doesn't compress so that takes 1 tape.

See next comment:

Author Comment

ID: 34248144
Who makes archival DVD's? I would save the key to at least 4 places on and off site.

Loved the change for a $100.00 dollar bill!

Author Comment

ID: 34248322

Part of my pain is setting the over write period. If I set my 12 dailys to 6 days. My weekly rotate out to 28 days and my monthly to 365 days.

So your basing a 10 month rotation over the 12. My library can handle 28 tapes so keeping FB's for a week and rotaing out the Saturday set would work.

After 6 days I would always have 2 tapes available but I should keep 12 days of weekly in the library. 24 Tapes. Then have another 24 tapes for my monthly off site. Now I have 48 tapes putting in 2 new tapes each month. I would then have 8 weekly tapes that are rotated to the fire safe for 28 days. Which is 16 tapes so I really need  64 tapes to maintain the over write periods. Rotating in 2 new tapes or I will hit lock down on my backup is 3 months?

Everything is SCSI 320 on the backup. The RAID 5 is SATA with a big stripe. It is all local so no bandwidth issues. No money for tapes so D2D2T is a pipe dream for this IT Department.
LVL 18

Expert Comment

ID: 34248945
I am not sure of your rewriting of my suggestion...

I suggested to (1 + 2b above) :
-Have 6 days of full compressed backup + 1 uncompressed backup on disc
==> No tape + (7x1.5TB=) 11TB backup disc space (8x2TB for 12TB in RAID6)

-Have a weekly (2 tapes) backup (from the daily disc one) that is stored offsite
==> (2-tapes x 20 = 40 tapes offsite with 10 month + 10 weeks for a full year) + 2 tapes ready to handle the next set + 2 tapes (spare or to-be-offsite-soon) = 44 tapes grand total

Once a week, you :
-put in the spare set for it to be ready for next week tape backup and take your new set of 2-tapes offsite
-get back with the weekly-or-monthly obsolete 2-tapes that becomes your new spare set onsite

==> To reduce this 44 tapes to 34 tapes, you can lower the weekly sets to 4 weeks and add a monthly one (Monthly covers 2 to 12 months backward)

==> To reduce this 44 tapes to 30 tapes, you can lower the weekly sets to 4 weeks, add a monthly one and remove 1 on 2 monthly older than 7 months (Monthly tapes would cover 2 to 7 months backward and 9-11-13 or 8-10-12 alternatively)

Author Comment

ID: 34251287
Well it was more for me to think it through. I don't have the disk space to do an uncompressed backup to disk. My other issues is my GIS info is already compressed so I get 1:1 ratio on it. That is about 800 GB's so doing HW compression, which I do, doesn't do squat for that info.

I am rereading your post to see how I can get it to work. I am not sure of any legal obligation I have to maintain a 12 month of backups. Sure don't want to tell the big boss in a litigation issue "What files from when" of course that could go either way.

Author Closing Comment

ID: 37720162
D2D with deduplication is the way to go. For now it is the tape library. The good thing is i can easily store tapes off site. Doing a D2D over the WAN on the weekend might work.

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