What are the advantages/disadvantages of scattering and gathering?

[Huy]

I'm watching some unRAID tutorials from spaceinvaderone and in his video about essential disk utilities, he mentions the unBALANCE tool. It basically is a GUI to easily scatter or gather certain shares (from) across the disks.

 

Since I've only started using unRAID (and was only using Windows for gaming and office work earlier), I'm wondering what benefits using this tool could have? On a normal office PC with Windows, gathering would obviously advantageous since all related files are on the same disk. However, user shares seem to exactly solve this problem: The files can be scattered across disks yet still are grouped together in a "folder".

 

 

Surely, there must be very good reasons to use unBALANCE. What are some reasons to use the scattering tool, and what to use the gathering tool?

 

[Ashe]

I’ve used the scatter element when adding 8TB drives to my array for moving data off several 3TB drives so that I can later remove the empty 3TBs from the array.

I haven’t used the gather yet, but through lack of planning my music folder is spread across multiple disks and I would like it to be on one disk only so that only one disk is spun up when using the music folder


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[pyrater]

Advantage of gathering = Only one disk needs to be spun up as "older" data is on other drives that is not used that often.  IE Old tv shows are on disk 1 but new tc shows are on disk 5. Disk 5 will be spun up almost all the time while disk 1 is never really used.

 

Advantage of scattering = Increased throughput, 2 streams from different drives vs 2 streams from the same drive.  Also since your drives are more balanced (less full) you will not have the speed of the drive fall off at the edge of the platter as much. (Think 50% full vs 90%)

 

In the words of linkin park. In the end it doesnt really matter.  

Edited February 13, 2018 by pyrater

[Huy]

I never spin down my disks anyways, so would I have no advantage at all from gathering e.g. all old TV shows on one disk and all new TV shows on a different one? Would I be better off scattering all new TV shows on several disks to increase throughput?

[JonathanM]

2 hours ago, Huy said:

Would I be better off scattering all new TV shows on several disks to increase throughput?

Does your intended use include direct streaming multiple shows simultaneously? If so, putting those shows on different physical disks could make sense.

[SSD]

I am a gatherer (like to keep logical files together). One reason, in the case of multiple drive failure, the disks that survived would have "complete" sets of files, and not part of this and part of that.

[S80_UK]

1 hour ago, SSD said:

I am a gatherer (like to keep logical files together). One reason, in the case of multiple drive failure, the disks that survived would have "complete" sets of files, and not part of this and part of that.

 

Agree - This also extends to any disks that are lost.  It can then be much easier to identify what might need to be recovered from backups / re-ripped / etc in such a case.  

[Squid]

1 hour ago, SSD said:

One reason, in the case of multiple drive failure, the disks that survived would have "complete" sets of files, and not part of this and part of that.

Of course the reverse is also true.  In lieu of backups you're far better off losing some files and not all

[pwm]

20 minutes ago, Squid said:

Of course the reverse is also true.  In lieu of backups you're far better off losing some files and not all

I prefer to get a total loss of 10 titles than suddenly have 100 partial titles.

 

Especially since I'm expected to have backup and it's so much easier to read back 10 titles from backup than to read back 100 partial title.

[Squid]

2 minutes ago, pwm said:

I prefer to get a total loss of 10 titles than suddenly have 100 partial titles.

You've obviously never accidentally deleted all of your baby pictures without a backup handy...

[pwm]

1 minute ago, Squid said:

You've obviously never accidentally deleted all of your baby pictures without a backup handy...

No and no.

 

With layered storage I can't accidentally delete archived files. It's hard to manage even intentionally, since the archives are write-protected. And when it comes to photos, I even have to grab a sandpaper since I store copies on optical disks. M-Disc is a nice technology for long-time archival of critical data.

 

Human errors are the #1 cause of data loss. So priority #1 has to be to plan for a human-safe storage solution where even a very clever (or evil) human will have a hard time erasing the data.