Where yahoo and gmail are keeping the mails of there customers?

If it is in hard disk, what will be the capacity?

Where yahoo and gmail are keeping the mails of there customers?
On the Hard disk of their mail server
Reply:Emails aren't that large and hard drives keep getting larger. Some are now 500 gigabyte - they'll hold a lot of emails and they can be daisy chained, or so I'm told. Even on a normal PC, you can connect 4 hard drives in theory giving you around 4,000 gigabyte of space. A lot of emails. I understand that some servers have rows of even larger SCSI hard drives that act as mail servers and also for web space.

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