Raid 5 question

Ish · 21 Jul 2017 at 10:53

Hi

If we have a server that has 3 x 2TB hard discs in Raid 5 how many drives would need to be added to increase server space to 4TB?

The server had 8 hot swappable bays.

Armageus · 21 Jul 2017 at 11:16

Is this a trick question?

In Raid 5 you lose 1 disk worth of capacity. So 3x2TB = 6TB, but lose 2TB capacity = 4TB.
You also lose some logical space due to formatting overhead etc - but should have 3.7TB or so available.

Adding 1 more disk will increase it to 6TB, leaving around 5.7TB usable.
(NOTE: To add another disk, you will need to perform a migration, which WILL expose your data to risk, and you may need to purchase a Battery/Capacitor module if your raid controller doesn't already have one fitted)

Just to bear in mind though - RAID5 for most things is a bad idea. Ideally you should migrate it to at the least RAID6 (to prevent a double drive failure causing data loss), or if possible RAID1 / RAID 10.

Ish · 21 Jul 2017 at 11:54

Not a trick question. I'm not too clued up on Raid.

Our current server is goingto be upgraded from SBS2011 to Server 2016.

Ideally what we would like is to have 4TB of space and then if extra space is needed we just plug in another drive(s) without having to do anything else. Is this possible and if so with which Raid option? We also don't want things to stop if one drive goes down.

PiKe · 21 Jul 2017 at 11:57

You can't just extend a RAID in that way. You have to decide on how much space you need beforehand.

#Chri5# · 21 Jul 2017 at 12:10

Current server upgraded? Is somebody rebuilding it from scratch to go from SBS to 2016?

Ish · 21 Jul 2017 at 12:37

#Chri5# said:
Current server upgraded? Is somebody rebuilding it from scratch to go from SBS to 2016?

The current Dell server is having new hard drives put in and Server 2016 installed.

It's just used as an AD, file & print server by about 10 people.

PiKe said:
You can't just extend a RAID in that way. You have to decide on how much space you need beforehand.

OK, that makes sense.

PiKe · 21 Jul 2017 at 22:07

Are you not going to migrate it properly?

Ish · 21 Jul 2017 at 22:46

PiKe said:
Are you not going to migrate it properly?

It will have a clean reinstall as it is just a really basic setup.

The Dell T310 server has a PERC H200 RAID card. Will this work with WD Gold 6TB sata drives and if not which Dell raid card should be used?

Thanks for all the help so far everyone.

Armageus · 21 Jul 2017 at 22:53

You should be looking at dell drives rather than buying WD etc otherwise you may run into issues further down the line.