Author Topic: Are you using the right FlexRAID product?  (Read 18131 times)

Offline Brahim

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8,547
  • Karma: +204/-16
    • View Profile
Are you using the right FlexRAID product?
« on: September 03, 2015, 01:30:12 am »
Are you using the right FlexRAID product?

As you well know, FlexRAID is now a family of products with the core products being RAID-F (RAID over File System) and tRAID (Transparent RAID).

RAID-F (RAID over File System)
RAID-F is the first product we developed and is popular due to its flexible features as well as its ground breaking concept that is Snapshot RAID. RAID-F also has experimental real-time RAID, which is now being redesigned in order to get it out of experimental status.
As it stands, however, RAID-F is mostly Snapshot RAID and Snapshot RAID must be fully understood as a solution before adopting it.

tRAID (Transparent RAID)
Transparent RAID provides exclusively real-time RAID. Transparent RAID is also flexible and very energy efficient (only one disk needs to spin on READ and two on WRITE).
Transparent RAID was created with great purpose. It is much more general purpose solution than RAID-F currently is. When redesigned, real-time RAID-F might change things a bit. However, as they stand, tRAID should be the solution for real-time RAID purposes and RAID-F for Snapshot RAID purposes.

Snapshot RAID vs Real-Time RAID
Many users have come to FlexRAID from recommendations from other users who are successfully using it. From various reports, however, we are getting a sense that many users are making their product choice based on what others are running rather than which product they actually need.
It is extremely important that each potential user selects the right product based on his/her particular use case as the wrong solution will only bring frustrations.

In particular, Snapshot RAID has certain limitations that must be fully understood before it is adopted as a solution: http://wiki.flexraid.com/2011/10/18/understanding-the-limitations-of-snapshot-raid/
Data that you only add, rename, delete, move is fine under Snapshot RAID. These operations typically won't affect parity and one's ability to restore successfully (deletes are fine if the recycle bin feature is enabled). Data that you edit is typically not safe as it compromises parity.
Any time you have data that you edit in a Snapshot array, you must immediately sync the parity. Ideally, you should really exclude that data from the Snapshot.
Ultimately, we find that some users tend to underestimate the amount of dynamic data they have or simply fail to properly setup their data exclusions. That last part, is extremely important. When using media cataloguing tools such as MyMovies and the likes, you should realize that those tools make use of metadata files that should be excluded from Snapshot RAID as that data is considered dynamic data. These metadata files are heavily edited by the tools that manage them.

The two most important topics when using Snapshot RAID are:
1. http://wiki.flexraid.com/2011/10/18/understanding-the-limitations-of-snapshot-raid/
2. and http://wiki.flexraid.com/2011/06/04/understanding-exclusion-patterns/

Even though Snapshot RAID comes with maintenance tasks, things should run in a trouble free fashion. In fact, whenever Snapshot RAID becomes too much maintenance, it means that it is no longer the right choice for your use case. Snapshot RAID was designed for a very specific purpose: protect static or semi-static data.
If your Snapshot RAID maintenance tasks aren't running smoothly, please do not take it lightly. Look into the specific issues and resolve them in a timely manner or make the switch to Real-Time Parity.
Keeping your Snapshot RAID-F array healthy is primordial. Snapshot RAID would not be as popular as it is today if it did not work. Not only that, testing that it works is truly child play. So, you don't have to take someone else's word for it - you can actually test it out for yourself pretty easily.
If you find yourself struggling maintaining a smoothly running Snapshot RAID, it is tell tell sign that you are using the wrong solution for your particular deployment.

Real-Time RAID is much more forgiving than Snapshot RAID since there is no restriction on the type of data that can be part of the array. For users new to RAID, Real-Time RAID is the safer route to take. This is why, when recommending FlexRAID products to people new to RAID, we ask that you please recommend tRAID. This is unless you are sure they have a use case which Snapshot RAID is for as well as being sure those users won't violate the rules of Snapshot RAID and use it successfully.
« Last Edit: September 07, 2015, 01:28:43 pm by Brahim »