Virtualization and storage size

[cookie_monster]

As some of you probably know we're in the planning stage of virtualizing (at least some of it) our network, I'd appreciate some opinions on storage size from people that are already running a virtual setup.

 

To start we will be virtualizing five servers more than likely running server 2008, how much storage should I be planning for do I need to plan for the OS partition e.g 40 Gb and a snapshot. What sort of storage overhead should I anticipate per image?

I'm just talking about the OS here not the associated data. The servers will be 1 or 2x file servers, 2x DC's and a WSUS/AV server.

 

We currently have a Sun 7110 SAN which I think will give us approx 1.4 Tb of storage should this be enough?

 

Any opinions or suggestions appreciated.

 

Thanks

 

Grant.

[FN-GM]

For the OS 40GB will be fine you can extend if needed. As for the files you can only answer that.

 

TIP: I will be very careful using snapshots with servers especially DC's you can cause major problems with AD

[Butuz]

Planning on using 40GB for each server's OS partition here. Not converting our DC's over at the moment, so really I won't be using too much space on the SAN to begin with - just several C: drives for member and terminal servers.

 

Butuz

[tmcd35]

I tend to use use expanding disks, only use as much space as needed rather than fixed size, with a 12Gb limit for the OS partition. Never used all 12Gb in an OS partition - typically maxes out at around 8/9Gb. If I ever did reach the 12Gb limit I'd just extend the limit to about 20Gb.

[Theblacksheep]

40GB will be fine, maybe a tad large for C but not overall.

 

I've made 25GB C drives for server 2008 DC, default install and updates leaves 11GB free. You may want to consider a fixed page file size or a page on a seperate disk as fragmentation still has an impact on the C drive. Plus a data disk for service programes, on a seperate iscsi controller if it something like sql, exchange, sccm, wsus etc. To go the extra mile you can chuck all page file disks on a dedicated fast lun.

 

1.5T will run out quick.

Edited May 1, 2009 by Theblacksheep

[cookie_monster]

@FN-GM - If snap shots are not recommended for DC's how do you backup your OS images?

 

 

Should I aim for either 30Gb partitions or dynamic then, is 40Gb a bit overkill?

[irsprint84]

Domain controllers are fine but I d advise to keep the forest root as physical

[tmcd35]

Domain controllers are fine but I d advise to keep the forest root as physical

 

...Why?

[cookie_monster]

Yeh we have a fairly new box that's the PDCe amongst other things and that's staying, we'll be virtualizing a couple of DC's though.

 

 

...Why?

 

MS amongst others recommend not virtualising your root DC, I think it's due to issues with active directory if your hypervisor goes under with all DC's on it could corrupt your entire directory.

Edited May 1, 2009 by cookie_monster

[Butuz]

@FN-GM - If snap shots are not recommended for DC's how do you backup your OS images?

 

You can actualy use snap shots on DC's - the problem is you would have to both create, and restore the snapshots on all DC's at exactly the same time otherwise if the snapshot time difference is greater than 5 mins you will end up with domain controller(s) dropping off the network and losing replication.

 

Basically, it can be done but it is very very dangerous, unless you have ultra tight change management processes in place - your better off not doing it at all.

 

Should I aim for either 30Gb partitions or dynamic then, is 40Gb a bit overkill?

 

If you used fixed partitions at least you know exactly how much space all your C drives take up, and thus how much free space you have. If you use dynamic - you could end up with multiple servers expanding their drives at the same time and possibly running out of space (if you don't have much space free on the SAN).

 

Butuz

[cookie_monster]

I'm hoping the 7110 can be setup as raid 5/6 and give approx 1.4Tb of storage, i've hardly had time to unbox it at the moment. I'm hoping this will be enough space with OS/snapshots and data.

[Butuz]

I'm hoping the 7110 can be setup as raid 5/6 and give approx 1.4Tb of storage, i've hardly had time to unbox it at the moment. I'm hoping this will be enough space with OS/snapshots and data.

 

Does the 7110 support Raid 6?

 

Raid 5 with one hot spare will give you 1.752 gig and the ability to have one drive fail at a time.

Raid 6 with two hot spares will give you 1.460 gig and the ability to have two drives fail at a time.

 

Write speed is slower on Raid 6 than on Raid 5 though due to the extra calulations the controller needs to do. Read speed is just the same on 6 or 5 (bloomin fast).

 

Butuz

[sircles]

Keep a spare controller in case the original goes nuts - RAID is great as long as it doesn't go wrong and then you realise you can just bung the disks in another server.

[cookie_monster]

Does the 7110 support Raid 6?

 

It says so in the book. It's a tough choice but I think I'll go RAID5 as I've a feeling every bit of space will count.

 

 

RAID is great as long as it doesn't go wrong and then you realise you can just bung the disks in another server.

 

I've had RAID setups go wrong before but that's what backups are for.

[FN-GM]

@FN-GM - If snap shots are not recommended for DC's how do you backup your OS images?

 

 

Should I aim for either 30Gb partitions or dynamic then, is 40Gb a bit overkill?

 

Yeh we have a fairly new box that's the PDCe amongst other things and that's staying, we'll be virtualizing a couple of DC's though.

 

We visualize all Sevrers with no problems

 

 

 

 

MS amongst others recommend not virtualising your root DC, I think it's due to issues with active directory if your hypervisor goes under with all DC's on it could corrupt your entire directory.

 

Backup how you would backup a normal DC

[linescanner]

@cookie_monster

 

These details will show you the kind of usable storage you can get out of the 7110 in various configs

 

Double-Parity RAID

 

* 11 Data: 1.45TB

* 1 Spare

* 2 Parity

* 11.4 RDPM

 

Double-Parity RAID Wide

 

* 11 Data: 1.45TB

* 1 Spare

* 2 Parity

* 11.4 RDPM

 

Mirrored

 

* 6 Data: 808GB

* 2 Spare

* 6 Parity

* 7.6 RDPM

 

Single -Parity RAID Narrow

 

* 10 Data: 1.32T

* 2 Spare

* 2 Parity

* 5.8 RDPM

 

Striped

 

* 14 Data: 1.84T

* 0 Spare

* 0 Parity

* 1.0 RDPM

 

In addition to the space calculations, the table contains a Relative Data Protection Metric (RDPM) which can be used to help determine how well the data is protected relative to the unprotected, striped data configuration.

 

The RDPM is derived from a Mean Time To Data Loss (MTTDL) model which is suitable for comparing to striped data sets. A higher RDPM number is better. It is not meaningful to compare RDPM across different components (rows) in the table.

 

Here is a link to show the full table for the 7110 and all options on the 7210 systems

 

Hope this helps

Edited May 2, 2009 by linescanner