Enterprise Vault Sizing Tool output - is this right?

Andy Joyce actually taught me this one, when I had the same question......

Indexes are based on a per user archive not a per item.

For example, if you have 2 users that have a 1 MB email, each user index will be 130kb (roughly) for a total of 260kb of total index against a 1 MB item. (See your message attachment SIS ratio)

So total storage is

800KB for the actual email (at 80% compression)

260 KB for the index of the 2 users

So it does look like the indexes are larger than 13%, more like 26% of the original item, but you have to take into account each user's individual index.

The use of SIS allows you to reduce the amount of storage required for the original item, but does not change the amount of space required for the use index.

The advantage of having a per user archive is that in the event of a corruption or disk failure, you only need to rebuild some indexes instead of one big index (which could take an extended period of time). Smaller indexes are less prone to corruption also.

You also have some monster size messages with lots of attachments to index

758KB for average message size is huge.

So be aware that your performance metrics wont be anywhere close. EV performance metrics are based on average message size of 70kb. For each doubling of the size, throughput drops by 1/3. Therefore the performance guide states 8 core CPU is roughly 50,000 items per hour at 70KB.

Without having to relearn calculus for the formula to figure out your expected performance, keep in mind it may look like EV is slow if you look at message throughput per hour.