A RAID 5 volume can only tolerate a single drive failure, because it operates using a single distributed parity block per stripe. Unfortunately, I would consider the data lost. However, if this data is critical or hasn't been backed up in a while, you could contact Drive Savers or ACE Data Recovery. I believe both of those companies offer discounts if you tell them that Dell referred you. 

If you use Drive Savers, I believe the general process is as follows:

You would send your drives to them, they can determine how much data they can recover, they would then generate a quote for you, then the drives and data would be sent back. I'm not sure about how long it takes, but I think it is a fairly quick process.

@darkog As suggested by Dylan, check if there is back up available.

1. Verify if the available backup can be restored: Restore the backup to a different location, preferably on a spare drive.
2. Verify the data after restore. If the data is clean and usable, proceed to the next
3. Repair the drives in a RAID In case the drives or disks cannot be repaired, then replace them with new disks. Replacing the drives with previously used drives may again create performance related issues. Such a situation is avoidable by testing the drives for performance and certify them for production.
4. Upload the data on the newly configured RAID.
5. Test the performance of RAID Array

Or in case of no intact backup, you can go for:

1. Attach all failed disks to the bootable disk
2. Recover content to the recoverable storage disk
3. Replace the existing disk with working drives
4. Rebuild and configure RAID as a duplicate of the original
5. Transfer the entire data from the bootable disk to the newly built RAID Array

Recovery should be performed only by Certified Professionals. If above does not help, try RAID recovery tool where you can verify the chance to recover data by using the free preview feature.

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