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Pat Shuff's Blog

Archive Storage Services vs Archive Cloud Services

Yesterday we started talking about the cost comparison for storage in the cloud. We briefly touched on the cost of long term archive in the cloud. How much does it cost to backup data for long term archive and what is the best way to do this? Years ago the default way of doing this was to copy your data on disk to a tape unit and put the tape in a box. The box was then put in an environmentally controlled room to extend the lifetime of tape and a person was put on staff to pull the data off the shelf when the data was needed. The data might be a backup of data on disk or a secondary copy just in case the disk failed. Tape was typically used to provide separation of duties required by Sarbanes-Oxly to keep people who report on financial data separate from the financial data. It also allowed companies to take large volumes of data, like seismic data, and not keep it on spinning disks. The traces were reloaded when geophysicists wanted to look at the data.

The first innovation in this technology was to provide a robot to load and unload tapes as a tape unit gets full or needs to be reloaded. Magazines were created that could hold eight tapes and the robots had bar code readers so that they could seek to the right tape in the magazine, pull it out of the series of tapes and inserted into the tape unit for reading or writing. Management software got more advanced and understood the bar code values and could sequence the whopping 800 GB of data that could be written to an LT04 tape. Again, technology gets updated and the industry moved to LT05 and LT06 tapes with significantly higher densities. A single LT06 could hold 2.5 TB per tape unit. Technology marches on and compression allows us to store 6 TB on these disks. If we go back to our 120 TB case that we talked about yesterday this means that we will need 20 tapes (at $30-$45 for each tape) and $25K for a single tape drive unit. Most tape drive systems support 8 tapes per magazine so we are talking about something that will support three magazines. To support three magazines, we need a second shelf in our tape storage so the price goes up by about $20K. We are sitting at about $55K to backup our 120 TB and $5.5K in support annually for the hardware. We also need about $1K in tape for the number of full and incremental backups that we want which would be $20K for four months of retention before we recycle the tapes. These tapes are good for a dozen re-writes so every three years we will need to repurchase tapes. If we spread the cost of the tape unit, tape drives, and tapes across three years we are looking at $2K/month to backup our 120 TB. We also need to factor in $60/week for tape pickup and storage fees at a service like Iron Mountain and a couple of $250 charges to retrieve tapes in the event of a catastrophic failure to drive tapes back to our data center from cold storage. This bumps the cost to $2.2K/month which is significantly cheaper than the $10K/month for network storage in our data center or $3.6K/month for cloud storage services. Unfortunately, a tape unit requires someone to care and feed it and you will pay that person more than $600/month but not $7.8K/month which you would with the cloud or disk solutions.

If you had a ton of data to archive you could purchase a tape silo that supported hundreds or thousands of magazines. Unfortunately, this expandability cones at a cost. The tape backup unit grew from an eighth of a rack to twenty full racks. There isn't much in between. You can get an eighth of a rack solution, a full rack solution, or a twenty full rack solution. The larger solution comes in at hundreds of thousands of dollars rather than tens of thousands.

Enter cloud solutions. Amazon and Oracle offer tape solutions in the cloud. Both companies offer the twenty full rack solution but only charge a per tape charge to consumers. Amazon Glacier charges $7/TB/month to store data. Oracle charges $1/TB/month for the same service. Both companies charge for data restoration and outbound transfer of data. The Amazon Glacier cost of writing 120 TB and reading back 10% of it comes in at $2218/month. This is the same cost as having the tape unit on site. The key difference is that we can recover the data by requesting it from Amazon and get it back in less than four hours. There is no emergency recovery charges. There is not the weekly pickup charges. We can expand the amount that we backup and the bulk of this cost is reading back the data ($1300). Storage is relatively cheap for our backups, we just need to plan on the cost of recovery and try to limit this since it is the bulk of the cost.

We can drop this cost even more using the Oracle Archive Cloud Services. The price from Oracle is $1/TB/month but the recovery and transmission charges are about the same. The same archive service with Oracle is $1560/month with roughly $1300 being the charges for restoring and outbound transfer of the data. Unfortunately, Oracle does not offer an un-metered archive service so we have to guestimate how much we are going to restore on a monthly basis.

Both services use REST apis to write, restore, and read data. When a container (Oracle Archive) or bucket (Amazon Glacier) is created, a PUT call is done to the endpoint of the service. The first step required by both are authentication to provide credentials into the service. Below we show the Oracle authentication and creation process through the REST api.


The important part of this is the archive header extension. This differentiates if the container is spinning disk or if it is tape in the cloud.

Amazon recommends using a windows based tool like s3browser, CloudBerry, or using a language like Java, .NET, or Ruby and their published SDKs. CloudBerry works for the Oracle Archive as well. When you create a container you have the option of pulling down storage or archive as the container type.


Both services allow you to encrypt and compress the data as it is written with HTML Headers changing the characteristics and parameters of the container. Both services require you to issue a PUT request to write the data to tape. Below we show the Oracle REST api.

For CloudBerry and the other gui based tools, uploading is just a drag and drop from your local file system to the tape storage in the cloud.

Amazon details the readback procedure and job system that shows the status of the restore request. Oracle has a similarly defined retrieval policy as well as an archive tutorial. Both services offer a 4 hour window to allow for restoration. Below is an example of a restore request and checking on the job status of the job spawned to load the tape and transfer the data for reading. The file is ready to read when the completedPercentage is 100.


We can do the same thing with the S3 browser and Amazon Glacier. We need to request the restore, check the job status, then download the restored files. The files change color when they are ready to read.



In summary, we have looked at how to reduce cost of archives and backups. We looked at using a secondary disk at our data center or another data center. We looked at using on site tape units. We looked at disk in the cloud. Today we looked at tape in the cloud. It is important to remember that not one of these solutions is the answer. A combination of any or all of them are needed. Daily and weekly backups should happen to a secondary disk locally. This data is most likely to be restored on a regular basis. Once you get a full backup or two under your belt, move the data to another site. It might be spinning disk, it might be tape but something needs to be offsite in the event of a true catastrophic failure like a communication link going out (think Dell PowerVault and a thunderstorm) and you loose your primary lun and secondary lun that contains your backups. The whole idea of offsite backups are not for restore but primary for insurance and regulation compliance. If someone needs to see the old data, it is there. You are betting that you won't need to read it back and the cloud vendors are counting on that. If you do read it back on a regular basis you might want to significantly increase your budget, pass the charges onto the people who want to read data back, or look for another solution. Tape storage in the cloud is a great way of archiving data for a long time at a low cost.

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