Explanation of Windows home server storage pool/protection

[stevieg]

Ok because i havent seen a very definitive descriptioin on how WHS does its data protection I set up a box last night to experiment and I really like it.

First off the hardware config is basically setup as a JBOD ie. no software or hardware "raid"

my setup is as follows

8 port sata2 pcix card
2x750gb sata2
1x500 sata2
1x320 sata2
total physical capacity of 2.3TB but lets round this down to 2.0tb for this explanation

WHS uses a folder protection mirror instead of disk mirroring. In my Storage Pool I have 2.0tb available and when I create network shares I can choose to have it protected or unprotected. In my case I chose to have my documents shared folder (photos etc) protected and my movies share unprotected.

for example my documents folder is 100gb, because it is protected it uses 200gb of my storage pool and mirrors that 100gb of data on two seperate physical disks to provide a drive failure protection, this leaves 1.8tb unused in my storage pool.

now my movies folder is 500gb and is configured to be unprotected (no mirroring), this uses as expected 500gb of my storage pool only and leaves me a remaining 1.3TB available in my storage pool.

IMO this is quite and efficient way of using the available disk space in a home network environment allowing me to protect the data I want to.

Steve

 

[Vette5885]

I've been with the WHS for about a year now, and think it's great. But there's more to it than that. I'll add...

A JBOD gives the notion that the drives are simply contiguous, without any form of specialization of any one drive. WHS is slightly different.

In a single drive configuration, the sole drive is partitioned in two: a 20GB system partition (which cannot be adjusted during the install) and the remainder as the DATA partition. When you copy files to your shares, the files are stored in the data partition, and that is that (ok, slightly more advanced than that, but atleast thats the idea. I'm pretty sure that the system will actually use the same configuration as the multiple disk scenario, as described below, but have everything in that one data partition instead of spread out amongst other drives)

In a multiple drive configuration, during the install, windows will choose the largest drive you have and configure it as above (dual partition, 20GB system + remainder as data). Each additional drive is then mounted as a folder within the Data partition, so that the drive extender only works with one traditionally(?) mounted drive (the D: drive). When you place a file onto the WHS, a "tombstone" (very poor name for it - AD admins should agree) is placed into a folder structure that corresponds with the shares on the system. The tombstone is a reference point to the actual file, which will be stored in one of the folder-mounted drives. This is done on a file to file basis, so your network share may span more than one physical drive (my TV folder is 515GB, but my largest drive for the longest time was 320GB). If you run out of space in the additionally mounted drives, then files will be stored on the first drive in the DATA partition.

Drive extender has a replication function that will duplicate all the files within a specified share on a second drive. Thus, if you have a 1GB file on the WHS, with folder duplication, it will take up File + Duplicate + Tombstone, or about 2GB. Note that the tombstones are very small (not entirely sure, but I think they're in the single-digit KB range, like 4KB).

In the event that you lose a drive, with folder duplication turned on, WHS simply has to rearrange the files and reduplicate them. If you lose the system drive, then WHS will be reinstalled on the C: drive (you currently lose eveything on C: if the first drive fails, but the Power Pack will allow you to backup the partition, somehow) and then recreate the tombstone listing.

There's even more to hoe some of this works, utilizing shadow copies, but I'm not entirely sure how that comes into the mix with DE. Then there's the single instance backup built into WHS, which in it of itself it priceless, as many members here will agree. Combine that with the easy to use, almost thoughless, customizable (with plugins) interface, and the fact it's a Server 2003 box (it'll run WSUS and SharePoint), and I think that WHS is a little piece of gold in the not-ready for the home server market.

Do note that despite loving the product, the file corruption issue scares the crap out of me and I'm very careful with file access (until Power Pack 1 comes out).