In these days of cheaper disk storage, is it really worth to have data on tape? Disk acquisition costs might be more (but hey..there are cheaper ones out there) and so is a tape library. Of course, if you already have any of these, the acquisition costs might not be a question.
Lower RTOs are achieved by employing disk-to-disk (D2D) technologies - even if data is remote / offsite. A better understanding of the backup-environment, backup-application, and needs can help in deciding which one is a better route. If the requirements are only to have 1-month (or 3-month) retention, and to have that data offsite, the most cost-efficient way to achieve it is D2D backups. Of course, you can do D2D2T if there is a permanent archival requirement.
Now, let us take a use-case of 50TB of data that need to be backed up with a 10% daily incremental growth and retention of 90-days.
Assuming, backup times need to be faster, you will need LTO-4 drives which has native speed of 120MB/s and can accommodate 800GB un-compressed (1.6TB compressed). If all the 50TB is from the same client and backup-policy, you will not need more than 1 or 2 drives. But in real life, that data is coming from several systems at the same time and hence you will need at least 4-6 drives (of course you can do multiplexing, but that will slow down the speeds).
With a 2:1 hardware compression, you would need approx 32 tapes to do 1-full backup + 10% incremental for 6 days = 16 tapes. For one week, it is approx 48 tapes consumed. Now, if they need to go offsite and if you need data available readily for restores, you will have duplicate them and send them offisite (maybe IronMountain). That will make it 96-100 tapes per week. With a 90-day retention (let's say 12-weeks) you would need at least 1200 tapes to start with. Each media costs approx $100 which makes it $120,000. Plus the tape library cost ~300,000. This and labor costs to change tapes daily, offsite costs make it approx 350K for 50TB backup to hold for 90-days
So, an LTO-4 tape library (STK/Quantun/IBM) with 6-drives and 90-day retention for 50TB backups, it is an investment of approx $400K.
In this case, time to backup 50TB is 115hrs and assuming data is sent in equal streams to all drives, it would be approx 20hrs. And then for duplicating tapes would be another 20-hrs. So your backups are running 40-hrs everyday (yes, that is correct!). You will now need to get more drives!!! Increased drives makes the cost go by at least 100K (backup licensing and hardware) - total of 500K
Now, let's do the disk-way.
You would need a VTL that can do site-site optimized replication (for offsite) and has de-duplication capabilities, can compress and integrate with Backup application for the replication component. Now, since the weekly backup size is 80TB (full+10%incr), you will need backend storage for the de-duplicated repository (SATA is good enough) of at least 80TB (to be on safe side) i.e 80 drives of 1TB or approx 6-disk shelves with 14-disks each. VTL space itself can be approx 10TB of FC/SAS. As backups keep coming in, the data can be de-duplicated and the VTL space will be freed up. Also, optimized replication can start at the same time.
With 4Gbps FC SAN, this can be done in 3.5hrs (with 10-virtual drives - add as many as you want - its free!!). Also, de-dup (using one of the VTL vendor's information), can be completed in 27hrs (this is for the entire 50TB), and minus backup-time= 23hrs. Also, at the end of 27hrs from start of backups, your entire 50Tb is also offsite (you don't need 40hrs per day). And with new backup application features, after the first full backup, you can follow the incremental-forever model and still have your full backups created on-the-fly or near-instantaneously. This will save tons of hours as well as the congestion/traffic on the LAN/SAN.
Now comes the good part, you dont need anymore storage space for further backups. All data that gets backed up daily, weekly is a duplicated backup. I have seen upto 9.5:1 ratios in such cases, and that means a 95% reduction in space requirements. So for your 90-day backup retention you just need approx 30-40TB of de-dupe repository ( with 2:1 compression as well) and not 80TB as I mentioned above.
So 2 sites with VTL appliances and 40TB SATA and 15TB FC/SAS costs approx 400-500K and backup licensing (if you do not have it already for VTL) approx 50-100K. Plus bandwidth costs approx 50-100K. So total solution costs is at the high-end 700K as opposed to 500K.
It may seem high cost initially but you are eliminating any manual intervention (or mucking) with your tapes. Also, tapes might not be readable when you need them!! And data is offsite within few hours of your backups. Finally, if the retention is a lot more than 90-days and if you do not have local hands-and-feet support, the cost benefits of having tape will significantly drop down.
Lower RTOs are achieved by employing disk-to-disk (D2D) technologies - even if data is remote / offsite. A better understanding of the backup-environment, backup-application, and needs can help in deciding which one is a better route. If the requirements are only to have 1-month (or 3-month) retention, and to have that data offsite, the most cost-efficient way to achieve it is D2D backups. Of course, you can do D2D2T if there is a permanent archival requirement.
Now, let us take a use-case of 50TB of data that need to be backed up with a 10% daily incremental growth and retention of 90-days.
Assuming, backup times need to be faster, you will need LTO-4 drives which has native speed of 120MB/s and can accommodate 800GB un-compressed (1.6TB compressed). If all the 50TB is from the same client and backup-policy, you will not need more than 1 or 2 drives. But in real life, that data is coming from several systems at the same time and hence you will need at least 4-6 drives (of course you can do multiplexing, but that will slow down the speeds).
With a 2:1 hardware compression, you would need approx 32 tapes to do 1-full backup + 10% incremental for 6 days = 16 tapes. For one week, it is approx 48 tapes consumed. Now, if they need to go offsite and if you need data available readily for restores, you will have duplicate them and send them offisite (maybe IronMountain). That will make it 96-100 tapes per week. With a 90-day retention (let's say 12-weeks) you would need at least 1200 tapes to start with. Each media costs approx $100 which makes it $120,000. Plus the tape library cost ~300,000. This and labor costs to change tapes daily, offsite costs make it approx 350K for 50TB backup to hold for 90-days
So, an LTO-4 tape library (STK/Quantun/IBM) with 6-drives and 90-day retention for 50TB backups, it is an investment of approx $400K.
In this case, time to backup 50TB is 115hrs and assuming data is sent in equal streams to all drives, it would be approx 20hrs. And then for duplicating tapes would be another 20-hrs. So your backups are running 40-hrs everyday (yes, that is correct!). You will now need to get more drives!!! Increased drives makes the cost go by at least 100K (backup licensing and hardware) - total of 500K
Now, let's do the disk-way.
You would need a VTL that can do site-site optimized replication (for offsite) and has de-duplication capabilities, can compress and integrate with Backup application for the replication component. Now, since the weekly backup size is 80TB (full+10%incr), you will need backend storage for the de-duplicated repository (SATA is good enough) of at least 80TB (to be on safe side) i.e 80 drives of 1TB or approx 6-disk shelves with 14-disks each. VTL space itself can be approx 10TB of FC/SAS. As backups keep coming in, the data can be de-duplicated and the VTL space will be freed up. Also, optimized replication can start at the same time.
With 4Gbps FC SAN, this can be done in 3.5hrs (with 10-virtual drives - add as many as you want - its free!!). Also, de-dup (using one of the VTL vendor's information), can be completed in 27hrs (this is for the entire 50TB), and minus backup-time= 23hrs. Also, at the end of 27hrs from start of backups, your entire 50Tb is also offsite (you don't need 40hrs per day). And with new backup application features, after the first full backup, you can follow the incremental-forever model and still have your full backups created on-the-fly or near-instantaneously. This will save tons of hours as well as the congestion/traffic on the LAN/SAN.
Now comes the good part, you dont need anymore storage space for further backups. All data that gets backed up daily, weekly is a duplicated backup. I have seen upto 9.5:1 ratios in such cases, and that means a 95% reduction in space requirements. So for your 90-day backup retention you just need approx 30-40TB of de-dupe repository ( with 2:1 compression as well) and not 80TB as I mentioned above.
So 2 sites with VTL appliances and 40TB SATA and 15TB FC/SAS costs approx 400-500K and backup licensing (if you do not have it already for VTL) approx 50-100K. Plus bandwidth costs approx 50-100K. So total solution costs is at the high-end 700K as opposed to 500K.
It may seem high cost initially but you are eliminating any manual intervention (or mucking) with your tapes. Also, tapes might not be readable when you need them!! And data is offsite within few hours of your backups. Finally, if the retention is a lot more than 90-days and if you do not have local hands-and-feet support, the cost benefits of having tape will significantly drop down.
