none
Need advice for tape backup strategy RRS feed

  • Question

  • Good morning all,

    I'm new to DPM and could use some advice on how to best utilize tape backups with DPM for short-term and long-term/offsite backups.

    The total size of the data I'm backing up is about 13TB.  I'm using LTO4 tapes, which takes about 17 to do a complete full backup.  I have 80 tapes that I can use.  The data I am backing up does not change very often, however, when there is a change, I want to capture it in my backups as soon as possible.

    My thought is to do short-term incremental backups over the course of two weeks up to a month, if possible.  Ideally at that point, instead of doing a second full backup as an offsite copy, I'd like to find a way that the system will just flag those short-term incremental backups as an offsite backup, and then prompt for new tapes to be put in to start the process over again.  Also, by the time I'm putting backups on tapes 78, 79 or 80, the backup on tape 1, 2 or 3 is expired so I can rotate it back in and re-use it.

    What I had been doing was not doing any short-term backups, but instead just doing long-term backups every two weeks, whether any new data was being backed up or not, and then I would put in a bunch of new tapes and do it again two weeks later.  However, I did not have my retention settings set right, so I would run out of usable tapes and therefore could not do any further backups.

    Could someone please give me some advice on how I should set up this protection group to meet the goals listed above?

    Tuesday, August 4, 2020 3:06 PM

Answers

  • Hi,

    Thank you for the information.

    Going only for long term may not be feasible for you since you have limited tapes available. I think the best option for you to go for a mixed protection. You can opt for short-Term and long term schedule as below:

    Take short-term backup "Daily incremental + Full backup" and keep the retention for 3 weeks:

    It will consume 1 tape for incremental and 17 tapes for the full backup each week. Since the Retention is 3 weeks, that means on the 4th week, the first 17 tapes will be expired and can be re-used in the library. 

    In Long term protection, you can have a tape backup every Month and keep the retention for 2 Months. Give the same schedule for Recovery Goal 1 as the short term full backup schedule so that it will only run the recovery goal 1 if 2 schedule falls on the same day. This will help you save 17 tapes for that day. 

    I have created below sheet which will help you understand the tape utilization:

    Total number of tapes used in the library on 4th week: 69-18 =51.

    Free Tapes available: 80-51= 29.After end of 2 months, it will again expire 17 tapes from Long term protection. 

    I hope this will help you strategies your tape backup schedule. Do let me know if you have any follow up queries :). Thanks.

    Regards
    Aayoosh Moitro


    Please remember to mark the replies as answers if they help and unmark them if they provide no help. This posting is provided "AS IS" with no warranties, and confers no rights.

    • Marked as answer by Tesdall71 Friday, August 7, 2020 10:03 PM
    Wednesday, August 5, 2020 5:44 AM

All replies

  • Hi,

    It is difficult to suggest you a backup plan since I dont know the data types you are backing, churn/delta per week and if you are willing to use the tape compression option. keeping everything aside, I have prepare below schedule as per the information you have provided in your post but 80 tapes is quite less, you should consider buying some more tapes. You may use the logic and prepare your own data and should give some idea about the number of tapes you might need to achieve it. below are my suggestions:

    1. Short Term backup : Daily backups using incremental backup and keep retention for 4 weeks. By doing this you may need approximately around 20 Tapes to backups each day for one month. Below is the calculation:

    Assuming churn as 5% of 13tb each week:

    Churn = 4-5% every week = i.e. 4-5% of 13tb= 500 gb approx.
    Retention = 4 weeks = i.e. 500gb x 4 =2000gb is a week's churn/delta = 3 tape
    Full backup = 17 tapes for 13tb x 4 weeks = 68
    Total tapes required in a month = 68+3 = 71

    You can use Recovery goal 1 up to this point as you only have 80tapes in the library. If you buy more tapes, you can opt for Recovery goal 2 and have a longer retention range. Below is the calculation.

    2. Long term backups: Monthly backup and keep retention for 1 month: Monthly backup will be a full backup and it will copy the weekly full backup tape's content into a new tape (dataset Copy job). So it will require approx the same number of tape as above: i.e. 71. 

    By the end of the 2nd month, your all 71 tapes will be expired from Retention goal 1 i.e. Short term backup and can be re-used in recovery goal 1 or 2 respectively. 

    My suggestion would be to enable tape compression or use LTO5 or LTO 6 for more capacity on each tape.

    These data is based on assumption and may not be 100% accurate but logic remains the same. Let me know if you have any follow up questions. Thanks. 

    Regards
    Aayoosh Moitro


    Please remember to mark the replies as answers if they help and unmark them if they provide no help. This posting is provided "AS IS" with no warranties, and confers no rights.




    Tuesday, August 4, 2020 5:28 PM
  • Hi, thanks for replying and giving me some starting points.

    I omitted some details, which I should have probably given back in the beginning, and maybe this information will change your advice to a certain degree.

    First off, I'm using this in a homelab to make backups of video and audio files, for the most part, so these data types should already be compressed.  I'm backing up to a Dell TL2000 library with autoloader and dual LTO4 tape drives.  I can load the autoloader with 22 tapes.  As for data churn, I don't add very much to this file server I'm backing up on a weekly basis.  I add maybe about 200GB or so per month.  With this low amount of churn/data addition, would it make more sense to forego the short-term backups, and just do a regularly scheduled full long-term backup to take for offsite storage, given that I only have 80 tapes to work with?

    Or is it possible to do short-term backups for a longer period than one week?  For example, take a full backup at the beginning of the month and do incrementals for 2 weeks or the rest of the month, and then swap out all the tapes at the beginning of the next month and start over again?

    Thanks!

    Tuesday, August 4, 2020 8:22 PM
  • Hi,

    Thank you for the information.

    Going only for long term may not be feasible for you since you have limited tapes available. I think the best option for you to go for a mixed protection. You can opt for short-Term and long term schedule as below:

    Take short-term backup "Daily incremental + Full backup" and keep the retention for 3 weeks:

    It will consume 1 tape for incremental and 17 tapes for the full backup each week. Since the Retention is 3 weeks, that means on the 4th week, the first 17 tapes will be expired and can be re-used in the library. 

    In Long term protection, you can have a tape backup every Month and keep the retention for 2 Months. Give the same schedule for Recovery Goal 1 as the short term full backup schedule so that it will only run the recovery goal 1 if 2 schedule falls on the same day. This will help you save 17 tapes for that day. 

    I have created below sheet which will help you understand the tape utilization:

    Total number of tapes used in the library on 4th week: 69-18 =51.

    Free Tapes available: 80-51= 29.After end of 2 months, it will again expire 17 tapes from Long term protection. 

    I hope this will help you strategies your tape backup schedule. Do let me know if you have any follow up queries :). Thanks.

    Regards
    Aayoosh Moitro


    Please remember to mark the replies as answers if they help and unmark them if they provide no help. This posting is provided "AS IS" with no warranties, and confers no rights.

    • Marked as answer by Tesdall71 Friday, August 7, 2020 10:03 PM
    Wednesday, August 5, 2020 5:44 AM