Author Topic: FlexRaid2.0 how many parity drives are needed ? insufficient space-invalid file  (Read 1687 times)

Offline markm75

  • Jr. Member
  • **
  • Posts: 66
  • Karma: +0/-0
    • View Profile
I've got FlexRaid 2.0 set to expert mode with Raid TX.. i'm trying to understand exactly how many parity drives I should have given the amount of data drives.

As of now I have this configuration (i'm thinking i dont need 3, but i do need 1 of the 3 parity drives to be as big as the largest data size, which is why the one is 8TB as of now, otherwise I was getting insufficient space errors on re-creating parity):

Drive1:  Data, total size 4TB (3.63TB usable), 26.5GB free
Drive2:  Data, total size 4TB, 49.8GB free
Drive3:  Data, total size 4TB, 46.7GB free
Drive4:  PARITY, total size 4TB, 3.63TB free
Drive5:  Data, total size 4TB, 49.9GB free

Drive6:  Data, total size 8TB (7.27TB usable), 2.72TB free
Drive7:  Parity, total size 8TB , 7.27TB FREE
Drive8:  Parity, total size 4TB, 3.63TB free

So not only am I unsure on the Parity drives needed, but it seems my re-initialization, despite re-creating the whole Raid Configuration, has not regenerated parity so far (12 hours later)..

The command execution center says completed however.
If i do an update.. i get invalid  I:\flxr.meta file.. (i guess since initialization didnt work, update is useless here, so clearly an issue on initialization)

If i have 3 parity drives, do they ALL have to be at least as large as the largest DRU, or just one of them, if so, I guess in my current layout, i can only have 1 parity drive for the 5 data drives (not enough?)

Side question, do I also need a URU drive dedicated to all this as well? (edit, i guess this isnt directly related to recovering data that is lost, so doesnt apply here, fortunately I've never ran into actually recovering or using parity data yet)

edit: aside from the failure on "I" (despite formatting it and recreating the raid config), i DO now see space used for parity on my Drive7 (now it is showing 2.88TB free out of 7.27)

Any thoughts here?

Thanks in advance


« Last Edit: June 02, 2016, 09:55:52 am by markm75 »

Offline markm75

  • Jr. Member
  • **
  • Posts: 66
  • Karma: +0/-0
    • View Profile
I should add.. I recreated the raid config yet again.. i also wiped the 3 parity drives..

I get..

Error message: Invalid state: not enough usable space for parity! Space need: 829509795840

(meaning 829 GB needed?)

I thought i remedied this already by adding the 3rd parity drive that was 8TB in size, compared to the other two which are 4 each.

Something is still amiss here and still unsure if i really need 3, or just 1 single 8TB parity might be the fix?

Offline KingfisherUK

  • Jr. Member
  • **
  • Posts: 85
  • Karma: +7/-1
    • View Profile
Your parity drive(s) must be the same size or larger than the largest DRU. By the looks of your post, you have one 8TB parity and two 4TB ones, but there is an 8TB DRU so I suspect this is why it isn't happy.

How many parity drives you actually need is up to you and how much risk you want to take with your data. Personally, I have 11 DRU's (mixture of 4 x 1TB & 7 x 2TB drives) and 1 3TB PPU to allow for future expansion of the DRU's if needed. For my needs, this provides sufficient security; for someone else, maybe not.

Offline markm75

  • Jr. Member
  • **
  • Posts: 66
  • Karma: +0/-0
    • View Profile
Your parity drive(s) must be the same size or larger than the largest DRU. By the looks of your post, you have one 8TB parity and two 4TB ones, but there is an 8TB DRU so I suspect this is why it isn't happy.

How many parity drives you actually need is up to you and how much risk you want to take with your data. Personally, I have 11 DRU's (mixture of 4 x 1TB & 7 x 2TB drives) and 1 3TB PPU to allow for future expansion of the DRU's if needed. For my needs, this provides sufficient security; for someone else, maybe not.

Thanks.. yeah after recreating just now, with only 1 8TB parity, so far its still computing and no errors.. much further along.  I wasnt sure if the largest DRU rule meant that as long as ONE of the PPU's was that size or larger you were ok.. i guess it means all the parity drives must be at least that big then?

You mention the number of parity drives depends on how secure you want to feel.. but lets just say in my case.. with my 5 main data drives.. if two fail (say the 8TB and the 4TB drives), how does 1 single PPU of 8TB cover that data loss.. wouldnt you need Parity protection size that matches how much data you actually have, so say if i have 24TB of data, wouldnt i need 24TB of actual Parity space to protect (ALL) of it?  Confused on that part.. is that what is meant by how safe you want to be, in that a single 8TB might only cover parts of data here and there?  Unsure on this. 

You also mentioned having 1 PPU for future expansion of the DRU's, i'm not sure i understand how this relates to just adding another drive and designating it say DRU #6 (where in my case i had 5 before) in terms of the parity drive count..

 

Offline KingfisherUK

  • Jr. Member
  • **
  • Posts: 85
  • Karma: +7/-1
    • View Profile
When I referred to future expansion, I meant that by having a 3TB PPU, I can upgrade my 1 or 2TB drives to 3TB drives in future without having to upgrade the PPU.

In terms of security (if memory serves correctly) each PPU would cover one DRU failure; so having two PPU's would allow for two DRU failures, three PPU's - three DRU failures and so on.

Offline markm75

  • Jr. Member
  • **
  • Posts: 66
  • Karma: +0/-0
    • View Profile
When I referred to future expansion, I meant that by having a 3TB PPU, I can upgrade my 1 or 2TB drives to 3TB drives in future without having to upgrade the PPU.

In terms of security (if memory serves correctly) each PPU would cover one DRU failure; so having two PPU's would allow for two DRU failures, three PPU's - three DRU failures and so on.

Ah perfect, makes sense then.  so right now with my reduced PPU status from 3 to 1, its kinda like raid5 (though not as fast obviously, since its single drive performance).

I'll probably go with two 8tb PPU's then, to cover that two drive failure scenario.. thanks for the clarification.

Side note/question.. have you looked into flexraids newer offerings.. TRaid or Raid-F.. i still dont quite know if they are worth switching to.. i see the comparisons between those two, but nothing out there seems to compare them with raid tx (flexraid 2.0)

I guess unless somehow they offered faster performance almost raid5 or raid0 with parity but still able to recover and recreate the raid array without loss of data, then i would switch, otherwise unsure.

Offline KingfisherUK

  • Jr. Member
  • **
  • Posts: 85
  • Karma: +7/-1
    • View Profile
I'm actually running T-RAID, but did have FlexRAID before that, but ran that in a single PPU configuration as well. Raid-F is what's used in FlexRAID  ;)

As my usage patterns changed I needed more real-time data protection, whereas FlexRAID is more suited to static/archive data. When I upgraded my server, I bit the bullet and upgraded to T-RAID at the same time, haven't looked back since.

Ultimately, only you can say which suits your needs best. Have a look at the comparison table below, that should help:

http://flexraid.com/2013/10/04/table-comparison-of-transparent-raid-vs-raid-over-file-system/

Offline markm75

  • Jr. Member
  • **
  • Posts: 66
  • Karma: +0/-0
    • View Profile
I'm actually running T-RAID, but did have FlexRAID before that, but ran that in a single PPU configuration as well. Raid-F is what's used in FlexRAID  ;)

As my usage patterns changed I needed more real-time data protection, whereas FlexRAID is more suited to static/archive data. When I upgraded my server, I bit the bullet and upgraded to T-RAID at the same time, haven't looked back since.

Ultimately, only you can say which suits your needs best. Have a look at the comparison table below, that should help:

http://flexraid.com/2013/10/04/table-comparison-of-transparent-raid-vs-raid-over-file-system/

Yeah i've seen that chart, but what i really was hoping for was a comparison between what i'm using now with Raid TX.

Have you ever had to recover from a PPU, is it that hard.. ie: if i wanted to test, i guess i could disconnect a drive and go through recovery (i've never looked into this or tested, i guess i should).

Offline markm75

  • Jr. Member
  • **
  • Posts: 66
  • Karma: +0/-0
    • View Profile
Revisiting the parity ppu sizing issue.. could i take two of my 4TB drives and add them as another single PPU and act as one big 8TB, would this allow for creation of a second one that is essentially 8TB in size but two in one i wonder?

Offline KingfisherUK

  • Jr. Member
  • **
  • Posts: 85
  • Karma: +7/-1
    • View Profile
I'm not sure exactly what comparison you are looking for, so try the following links for more info:

http://flexraid.com/faq/

http://wiki.flexraid.com/

The FAQ has a more detailed explanation of the differences between FlexRAID (RAID-F) and T-RAID (Transparent Raid).


Offline markm75

  • Jr. Member
  • **
  • Posts: 66
  • Karma: +0/-0
    • View Profile
I'm not sure exactly what comparison you are looking for, so try the following links for more info:

http://flexraid.com/faq/

http://wiki.flexraid.com/

The FAQ has a more detailed explanation of the differences between FlexRAID (RAID-F) and T-RAID (Transparent Raid).

Ah never mind, i saw you mentioned Raid-F is what i have with 2.0 (raid tx) i guess.. so that does answer it :)


Offline markm75

  • Jr. Member
  • **
  • Posts: 66
  • Karma: +0/-0
    • View Profile
T raid looks better I suppose..

except this part maybe:

Can upgrade from a small drive to a bigger drive by just copying the data over and without affecting parity? No

Does this imply you cant have say 4, 4TB raid drives and add a 5th that is 5TB .. or does this mean if you swap out one of the 4TB for 5TB.. or in both cases you just have to do something with parity (which doesnt sound that much different than now)... i would think even now this is a No with Raid-F (it lists yes), as right now i'm going through the fact I have a larger drive in the mix and i have to make my parity larger to match or maybe thats two different things i guess.

I'm thinking it doesnt mean its not possible, just that there is a catch on parity recreation? (with Traid)



Offline KingfisherUK

  • Jr. Member
  • **
  • Posts: 85
  • Karma: +7/-1
    • View Profile
With RAID-F you could take a 4TB drive, copy all the data onto a new 5TB drive and swap them to increase the pool capacity, since parity is only calculated when scheduled to run or run manually.

With T-Raid, parity is calculated and updated in real-time so drive upgrades are slightly more complex (although still not all that hard).

Have a read-up on the wiki, it details all the procedures for replacing/upgrading drives under both systems.

In a nutshell, RAID-F is ideally suited to mostly static/archive data where scheduled parity updates will suffice. T-RAID is better suited to systems where data changes frequently/constantly as parity is updated in real-time.