Arq Frequently Asked Questions


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Does Arq re-upload everything each time it does a backup?

No; after the initial backup, Arq only uploads files that have changed.

What format does Arq use to store my data in S3?

Arq stores backup data in S3 in a format similar to that of the open-source version control system 'git'. This is for 2 reasons: de-duplication (to avoid redundant files on S3) and "packing" small files together (for less transaction overhead).

More details here: s3_data_format.txt

Does Arq properly back up all Mac metadata?

Yes. In fact, Arq is 100% Backup Bouncer compliant, unlike many other online backup offerings. Even Apple's Time Machine is not 100%.

Does Arq have a file size limit?

No. Arq can backup files of any size.

Does Arq have a bandwidth limit?

No, unless you tell it to. Arq can use all your available bandwidth to do backups, or you can choose to limit the transfer rate in the Preferences.

I chose to back up to Glacier, but all the data seem to be going to S3. Why?

Arq 4 stores all your data in your S3 bucket. Select your folder on the left in the Arq main window. If you see "Storage Type: S3 (Glacier storage class)"  or "Glacier" on the right, then Arq is uploading your data to a subfolder in your S3 bucket which has a "lifecycle policy" attached. The lifecycle policy tells Amazon to move those objects to Glacier storage class ASAP. Within a day or two after upload, Amazon moves the data and in the Amazon console you’ll see “Glacier” as the storage type for the objects. Arq 4 doesn't create any Glacier vaults, and you won't see anything in the Amazon Glacier console. Your billing statement will show Glacier charges within the S3 part of the bill.

Does Arq make bootable backups?

No. For a bootable backup we recommend SuperDuper. Arq is complementary to SuperDuper; SuperDuper creates a bootable backup on another hard drive, and Arq creates versioned backups online.

Duplicate Backup

A bootable backup is a duplicate of your hard drive. It's great if you need to get up and running very quickly in the event of a hardware failure -- you just boot from the backup. But you have to plug in your FireWire or USB drive and update the bootable backup, or it gets out of date quickly.

Versioned Backup

Arq does versioned backups of the folders you choose. This provides insurance against damaged or accidentally deleted files. A duplicate backup would just copy the damage and delete the same files, but with a versioned backup you can "go back in time" and get the undamaged/undeleted file.

Arq backs up to S3, so there's no need to remember to plug in a USB drive -- it backs up as long as there's an internet connection. The best backups are the ones that actually get created, after all.

Arq retains versions similar to the scheme used by Time Machine -- hourly for the past 24 hours, daily for the past month, and weekly until you reach the S3 budget you've chosen in the Preferences.

If you only use Arq for your important files and your hard drive fails, you'll have to replace the hard drive and install OS X from DVD, and then restore your important files from Arq backups; this would take longer than simply booting from an external drive.

Haystack Software LLC