Ugly Hedgehog® - Photography Forum
NAS Backup - Explanation Needed
If you want to reply, then register here. Registration is free and your account is created instantly, so you can post right away.
Page: 1 2 next>>
Apr 9, 2016 12:24:45   #
jerryc41 (a regular here)
 
I have two computers backed up to an NAS. I clicked on Properties of this backup on the NAS, and this is what it showed. I can understand the 894 GB, but what does the "23.3 TB on disk" mean? The NAS has two drives of 2 TB each, and my computer has an internal 4 TB D drive.



| Reply
Apr 9, 2016 13:15:05   #
Dngallagher
 
jerryc41 wrote:
I have two computers backed up to an NAS. I clicked on Properties of this backup on the NAS, and this is what it showed. I can understand the 894 GB, but what does the "23.3 TB on disk" mean? The NAS has two drives of 2 TB each, and my computer has an internal 4 TB D drive.


Could actually be due to wasted space. because of cluster size...

http://www.howtogeek.com/180369/why-is-there-a-big-difference-between-size-and-size-on-disk/

| Reply
Apr 9, 2016 13:26:45   #
jerryc41 (a regular here)
 
Dngallagher wrote:
Not knowing your backup scheme used or the software you are using....

The 894 GB is most likely the file size of the compressed backup on the disk, the 23.3 TB is the actual size of the uncompressed data....

When I say compressed it may be actually compressed, de-duped or a combination, depending on the backup software.

I use SyncBack SE. The backed up data is just about the same size as the data on my D drive, and nothing is compressed. I can't understand the 23.3 TB. That's huge.

When I look at the folders on D, the actual size and "on disk" size are virtually identical. I have a 4 TB D drive.

| Reply
Apr 9, 2016 13:28:35   #
Dngallagher
 
jerryc41 wrote:
I use SyncBack SE. The backed up data is just about the same size as the data on my D drive, and nothing is compressed. I can't understand the 23.3 TB. That's huge.

When I look at the folders on D, the actual size and "on disk" size are virtually identical. I have a 4 TB D drive.


My error... forgot about the cluster size issue with disks.... amended my answer above...

check this link...

And yes, 23 TB does seem HUGE... might be something else going on... have your tried a restore to confirm your backup is good?

http://www.howtogeek.com/180369/why-is-there-a-big-difference-between-size-and-size-on-disk/

Could the discrepancy be simply that the cluster size on the NAS backup is different from what Windoze knows about so looking at property in Windoze will always report incorrectly based on the cluster size used by the NAS?

| Reply
Apr 9, 2016 14:13:50   #
jerryc41 (a regular here)
 
Dngallagher wrote:
And yes, 23 TB does seem HUGE... might be something else going on... have your tried a restore to confirm your backup is good?

Could the discrepancy be simply that the cluster size on the NAS backup is different from what Windoze knows about so looking at property in Windoze will always report incorrectly based on the cluster size used by the NAS?

Yes, I did a backup to another computer last week, and it worked fine. I'll look at that link.

| Reply
Apr 9, 2016 16:51:28   #
TriX (a regular here)
 
Dngallagher wrote:
My error... forgot about the cluster size issue with disks.... amended my answer above...

check this link...

And yes, 23 TB does seem HUGE... might be something else going on... have your tried a restore to confirm your backup is good?

http://www.howtogeek.com/180369/why-is-there-a-big-difference-between-size-and-size-on-disk/

Could the discrepancy be simply that the cluster size on the NAS backup is different from what Windoze knows about so looking at property in Windoze will always report incorrectly based on the cluster size used by the NAS?
My error... forgot about the cluster size issue wi... (show quote)


That's a very good answer. The default NTFS cluster size is 4KB, whereas an external NAS may have a selectable cluster size, say anywhere from 4-64KB (or larger). The downside of large cluster size is that if your file is 65KB, with a 64KB cluster size, it takes 2 clusters, wasting 63KB, whereas a 4K size would use 17 clusters, wasting 3KB. Like everything else in computing, there are compromises... The upside of large cluster size for large files is typically faster performance, especially if the clusters are not contiguous on disk (requiring extra seeks).

| Reply
Apr 10, 2016 07:59:44   #
jerryc41 (a regular here)
 
TriX wrote:
That's a very good answer. The default NTFS cluster size is 4KB, whereas an external NAS may have a selectable cluster size, say anywhere from 4-64KB (or larger). The downside of large cluster size is that if your file is 65KB, with a 64KB cluster size, it takes 2 clusters, wasting 63KB, whereas a 4K size would use 17 clusters, wasting 3KB. Like everything else in computing, there are compromises... The upside of large cluster size for large files is typically faster performance, especially if the clusters are not contiguous on disk (requiring extra seeks).
That's a very good answer. The default NTFS cluste... (show quote)

I don't remember having a choice of cluster size when I set up the NAS. Still, where did it get that 23.3 TB figure?

| Reply
Apr 10, 2016 08:02:58   #
jerryc41 (a regular here)
 
Dngallagher wrote:
http://www.howtogeek.com/180369/why-is-there-a-big-difference-between-size-and-size-on-disk/

Could the discrepancy be simply that the cluster size on the NAS backup is different from what Windoze knows about so looking at property in Windoze will always report incorrectly based on the cluster size used by the NAS?

The link provides a good answer, if someone is using FAT, which I'm not.

| Reply
Apr 10, 2016 08:05:21   #
Dngallagher
 
jerryc41 wrote:
I don't remember having a choice of cluster size when I set up the NAS. Still, where did it get that 23.3 TB figure?


You may not have a choice, but do you know what it is? the number of files multiplied by the cluster sizes tells you how much actual disk space is being taken up, as the link describes.

Can you look at stats from the NAS device, not a client windows computer? THAT may show different info, and the real problem is windoze is just not converting space on disk properly - after all,, if out is a 2 TB disk, it is tough to use 23 TB isn't it?

| Reply
Apr 10, 2016 08:09:11   #
Dngallagher
 
jerryc41 wrote:
The link provides a good answer, if someone is using FAT, which I'm not.


The poster was using FAT in that instance.... you still have cluster size to enter into your equation....

From MICROSOFT's web page ....

Summary
All file systems that are used by Windows organize your hard disk based on cluster size (also known as allocation unit size). Cluster size represents the smallest amount of disk space that can be used to hold a file. When file sizes do not come out to an even multiple of the cluster size, additional space must be used to hold the file (up to the next multiple of the cluster size). On the typical hard disk partition, the average amount of space that is lost in this manner can be calculated by using the equation (cluster size)/2 * (number of files).

If no cluster size is specified when you format a partition, defaults are selected based on the size of the partition. These defaults are selected to reduce the space that is lost and to reduce the fragmentation that occurs on the partition.

I think you need to find out what the NAS you are using is set up for and see if the info then fits what windoze is telling you no matter how wrong it is.

Edit:

I think you are seeing a driver or software glitch... seems it is not uncommon for Windoze to screw up with NAS devices.... :)

https//social.technet.microsoft.com/forums/windows/en-US/8bd3dab7-eb71-4ffb-90de-32d7f756cf69/windows-8-displays-wrong-disk-size-on-nas-drive


| Reply
Apr 10, 2016 08:21:39   #
zigipha
 
1. you have a 20x factor in used disk space; the only way this can reflect reality is
1.1 clusters have to be >20x different (4x vs 64k is only 16x)
1.2. files have to be very small (like ~4k)
2. Do you really have 23TB of storage?

Seems like a SW glitch.

| Reply
Apr 10, 2016 08:22:11   #
zigipha
 
you should be able to go to the NAS itself and get a status of how much used how much free etc

| Reply
Apr 10, 2016 08:43:08   #
Ed Chu
 
why not just call the manufacturer ?

| Reply
Apr 10, 2016 09:12:30   #
jerryc41 (a regular here)
 
zigipha wrote:
you should be able to go to the NAS itself and get a status of how much used how much free etc

I haven't been able to do that. The closest I can come is using Properties to see what is in each folder. I can't get the same info I get from a regular hard drive. When I look at "Diskstation," I can see the two main backup folders - for two computers. Clicking on either of them shows me the individual folders that have been backed up. Right-clicking and looking at Properties is the only way to see how much space is used, but there's no indication of space available, unlike what I see for a regular drive.

This isn't a problem. I was just wondering where that 23.3 TB figure came from.

| Reply
Apr 10, 2016 09:58:58   #
dcampbell52
 
jerryc41 wrote:
I have two computers backed up to an NAS. I clicked on Properties of this backup on the NAS, and this is what it showed. I can understand the 894 GB, but what does the "23.3 TB on disk" mean? The NAS has two drives of 2 TB each, and my computer has an internal 4 TB D drive.


Jerry, I'm not sure about the NAS setup. However, it could be that the drives are mirrored or they could be a disk Raid array. I have done many 5 drive Raid arrays where the total is less than the total of the 5 drives.. for instance: a 5 disk array in Raid 5 using 1 terabyte drives would give you a total of 4 terabytes storage... the other terabyte is used for storage. The data would be scattered over the 5 drives to reduce the chance of data loss on any one drive.
http://www.raid-calculator.com/default.aspx

Now, I'm not saying this is the issue but it could be.

Here is what I use;
http://www.amazon.com/WD-Cloud-EX4-Pre-configured-featuring/dp/B00G4JZ30S

| Reply
Page: 1 2 next>>
If you want to reply, then register here. Registration is free and your account is created instantly, so you can post right away.
UglyHedgehog.com - Forum
Copyright 2011-2019 Ugly Hedgehog, Inc.