Cache - To pool or not?

[Ockingshay]

One of the big features of V6 was the ability to be able to create a cache pool. My understanding of this is that it would give a simple form of protection if one of the cache drive blows up, you would be able to recover the data.

 

After my little faux par today, i was searching the forums and something that cropped up was the BTRFS isn't particularly great atm and there are some serious concerns in it's immaturity. So having bought a second drive and getting all ready create my shiny new cache pool i wanted to ask what the current concession is?

 

If BTRFS isn't the way forward, what would be the best way of protecting the primary cache drive? Can you cache pool with a different FS?

[CHBMB]

One of the big features of V6 was the ability to be able to create a cache pool. My understanding of this is that it would give a simple form of protection if one of the cache drive blows up, you would be able to recover the data.

 

After my little faux par today, i was searching the forums and something that cropped up was the BTRFS isn't particularly great atm and there are some serious concerns in it's immaturity. So having bought a second drive and getting all ready create my shiny new cache pool i wanted to ask what the current concession is?

 

If BTRFS isn't the way forward, what would be the best way of protecting the primary cache drive? Can you cache pool with a different FS?

 

Personally I haven't got a cache pool.  But I backup my appdata via a script on cron once a week. 

[itimpi]

One of the big features of V6 was the ability to be able to create a cache pool. My understanding of this is that it would give a simple form of protection if one of the cache drive blows up, you would be able to recover the data.

 

After my little faux par today, i was searching the forums and something that cropped up was the BTRFS isn't particularly great atm and there are some serious concerns in it's immaturity. So having bought a second drive and getting all ready create my shiny new cache pool i wanted to ask what the current concession is?

 

If BTRFS isn't the way forward, what would be the best way of protecting the primary cache drive? Can you cache pool with a different FS?

there seem to be mixed views about the maturity of BTRFS, but many people seem to find it OK.    At the moment it is the only option in unRAID to give you redundancy on the cache - neither xFS or ReiserFS support pooling. If you do not want pooling then it may be better to stick with XFS on the cache.

[Ockingshay]

there seem to be mixed views about the maturity of BTRFS, but many people seem to find it OK.    At the moment it is the only option in unRAID to give you redundancy on the cache - neither xFS or ReiserFS support pooling. If you do not want pooling then it may be better to stick with XFS on the cache.

 

On the odd occasion i've had to mess about with my appdata (and therefore back it up), i have always found programs like plex and headphones take an absolute age to copy because of the thousands of files that make up their config directories.

 

One of the complaints was with sudden powerloss, but i have UPS, so i'm not really sure what the best way to protect my app data is.

[beire]

I was under the impression that docker.img needs a btrfs fs for a reason do not remember.

 

But lately I'm reading a lot of reply's that seem to point out that this is not true.

Is is better for docker to use btrfs or not?

[BRiT]

I was under the impression that docker.img needs a btrfs fs for a reason do not remember.

 

But lately I'm reading a lot of reply's that seem to point out that this is not true.

Is is better for docker to use btrfs or not?

That is no longer required. Docker.img uses btrfs filesystem internally. But the file itself can reside on any filesystem type.

[spylex]

Personally I haven't got a cache pool.  But I backup my appdata via a script on cron once a week.

 

This sounds like a great idea for a plugin of sorts, is there one or did you manually enter cron jobs?

[CHBMB]

Personally I haven't got a cache pool.  But I backup my appdata via a script on cron once a week.

 

This sounds like a great idea for a plugin of sorts, is there one or did you manually enter cron jobs?

 

It was a script that someone posted on here last year sometime..

 

#!/bin/bash
appdata=/mnt/cache/.appdata/
LogFile=/mnt/cache/cache_backup.log
BackupDir=/mnt/disk8/backups/appdata/

echo `date` "Starting cache drive backup to " $BackupDir >> $LogFile

#Stop plugin services located in /etc/rc.d/
# enter in plugins to stop here, if any
# /etc/rc.d/rc.plexmediaserver stop >> $LogFile


#stop dockers

  # find running docker containers
  declare -a Containers=(`docker ps -q`)

  # stop running containers
  for Cont  in "${Containers[@]}"
  do
    echo `date` " Stopping Container: " $Cont >> $LogFile
    docker stop $Cont >> $LogFile
  done


#Backup cache via rsync

/usr/bin/rsync -avrtH --delete $appdata $BackupDir  >> $LogFile

## RESTORE
## /usr/bin/rsync -avrtH --delete  $BackupDir  $appdata

#Start plugin services
# enter in plugins to start here, if any
# /etc/rc.d/rc.plexmediaserver start  >> $LogFile


#start dockers previousy stopped

  for Cont  in "${Containers[@]}"
  do
    echo `date` " Starting Container: " $Cont >> $LogFile
    docker start $Cont >> $LogFile
  done


echo `date` "Backup Completed " $BackupDir >> $LogFile

# send notification
/usr/local/emhttp/webGui/scripts/notify -i normal -s "Cache Drive Backup Completed" -d " Cache Drive Backup completed at `date`"

[kamhighway]

I set up a 2nd server so I could learn how to use plugins, dockers, vms, and cache pools without putting my main data at risk.

 

About a week ago, I set up a cache pool on this test server using 3 2TB hard disks. A couple of days ago, I changed the cache pool from the default setting of raid1 to raid0 to see if it would speed up access times for the hard drives enough to make them a good place to store vdisks for my vms. 

 

My main server uses an SSD to store my vdisks in order to make the vms feel responsive. The problem is that I would like to give each vm a big vdisk, but multi-TB SSD's are very expensive.  The big question is would the vms feel responsive or sluggish if their vdisks were placed on hard disks set up as btrfs raid0.

 

After a week of testing I have to say I am impressed! 

 

The hard disks I used are not the fastest models, but when they are in the btrfs raid0 cache pool the vms feel quite responsive. Although the ssd is still faster, the hard disks give me 6TB of space for vdisks instead of 480GB on the SSD.

 

What stops me from using this setup in production is that a few of the hero members here have said that btrfs is not mature enough to use in production.  But, those comments were made a while ago so things may be different now.

 

Question for the community:

 

Is anyone using a btrfs raid0 cache pool on their production server?