On Tuesday, 6 March 2018 6:29:11 PM AEDT Craig Sanders via luv-main wrote:
On Mon, Mar 05, 2018 at 10:54:10PM +1100, Andrew Pam wrote:
[ ... ] it's also possible to set up mirroring using LVM, btrfs or ZFS if you prefer.
With btrfs or ZFS it's easy to add additional drives for more space later.
With ZFS you only add them one RAID set at a time and after adding that RAID set can't be changed. You can't just add a disk at a time as you do with BTRFS. Last time I checked BTRFS RAID-5 and RAID-6 wasn't reliable IMHO.
Also, both btrfs and ZFS support transparent compression - which can greatly increase effective capacity if most of your data is uncomressed or poorly-compressed. Not video or audio files, for example.
The last time I ran a medium size mail server on ZFS I didn't see a lot of compression. I think it was something like 40%. Usually large amounts of data means video files though.
There are so many other benefits to using either btrfs or ZFS (snapshots, error-detection and correction, sub-volumes aka datasets, and much more), that IMO there's little reason to use a plain RAID-1 + ext4 partition for anything except a separate /boot.
Particularly as the most common errors are silent corruption which can't be detected by a plan RAID and can only be stopped by BTRFS or ZFS. Sucks for people who don't use Unix.
ZFS has the advantage of more features, and greater reliability. It's not built in to the kernel, but most distros have the kernel module packaged as a dkms package (ubuntu and a few others take the legally dubious stance that the CDDL vs GPL license conflict isn't a problem, so include ZFS pre-compiled with their kernels already).
I don't think it's legally dubious. Oracle know exactly what they are doing, if Oracle thought it was bad they would have let them know. -- My Main Blog http://etbe.coker.com.au/ My Documents Blog http://doc.coker.com.au/
On Tue, Mar 06, 2018 at 06:36:51PM +1100, Russell Coker wrote:
On Tuesday, 6 March 2018 6:29:11 PM AEDT Craig Sanders via luv-main wrote:
With btrfs or ZFS it's easy to add additional drives for more space later.
With ZFS you only add them one RAID set at a time and after adding that RAID set can't be changed. You can't just add a disk at a time as you do with BTRFS.
If you're using mirrored pairs, that's no problem - you'll always be adding or upgrading a pair of drives at a time. e.g. to go from RAID-1 with a single mirrored pair to RAID-10 with two mirrored pairs. or to add a third or fourth or fifth ... mirrored pair of drives. btrfs has greater flexibility in that it allows you to combine any combination of differently sized drives, and it's easy to rebalance your data across the new configuration.
Last time I checked BTRFS RAID-5 and RAID-6 wasn't reliable IMHO.
Still isn't. And I have my doubts about whether its raid-1 or raid-10 modes are entirely reliable either...i'm still seeing occasional reports of catastrophic data loss with btrfs that can't easily be dismissed as user error. RE: CDDL vs GPL
I don't think it's legally dubious. Oracle know exactly what they are doing, if Oracle thought it was bad they would have let them know.
"dubious" was the wrong word. "prohibited" is accurate. It's only "legally dubious" because, as you say, it's very unlikely that Oracle or anyone else with standing would sue. https://sfconservancy.org/blog/2016/feb/25/zfs-and-linux/ craig -- craig sanders <cas@taz.net.au>
On Tuesday, 6 March 2018 8:14:08 PM AEDT Craig Sanders via luv-main wrote:
With ZFS you only add them one RAID set at a time and after adding that RAID set can't be changed. You can't just add a disk at a time as you do with BTRFS.
If you're using mirrored pairs, that's no problem - you'll always be adding or upgrading a pair of drives at a time. e.g. to go from RAID-1 with a single mirrored pair to RAID-10 with two mirrored pairs. or to add a third or fourth or fifth ... mirrored pair of drives.
If you have any sort of enterprise use then you will have matched pairs. For home use it's pretty common to just use whatever you have available. If you have a home BTRFS RAID-1 setup you can just add a new disk at any time and after a balance operation the RAID-1 capacity will have increased by half the size of that disk. I have a spare 4TB disk sitting around for when I need an extra 2TB of usable space in my home server.
Last time I checked BTRFS RAID-5 and RAID-6 wasn't reliable IMHO.
Still isn't.
And I have my doubts about whether its raid-1 or raid-10 modes are entirely reliable either...i'm still seeing occasional reports of catastrophic data loss with btrfs that can't easily be dismissed as user error.
There are some situations where a system with memory errors will give moderate corruption on Ext3/4 but massive data loss on BTRFS. ECC is a good thing. Backups are good too.
RE: CDDL vs GPL
I don't think it's legally dubious. Oracle know exactly what they are doing, if Oracle thought it was bad they would have let them know.
"dubious" was the wrong word. "prohibited" is accurate. It's only "legally dubious" because, as you say, it's very unlikely that Oracle or anyone else with standing would sue.
Fair point, I hadn't seen that one before. Oh well my clients will be safe, their position is that they trust Canonical and will keep using it until/unless advised otherwise. -- My Main Blog http://etbe.coker.com.au/ My Documents Blog http://doc.coker.com.au/
On Tue, Mar 06, 2018 at 11:22:17PM +1100, Russell Coker wrote:
If you have any sort of enterprise use then you will have matched pairs.
I've been doing that at home for a long time. I resigned myself many years ago to always paying double the going price for storage because I always want RAID-1/mirrored-pairs. It means I have to put off some upgrades until I can afford, e.g. two x 4TB or two x 8TB drives instead of just one, but it is, IMO, worth it. OTOH, it does mean that when I upgrade my main machine, I have matched pairs of older drives to distribute amongst other machines. I'll probably be replacing a 4 x 1TB RAIDZ-1 pool with a pair of 8TB drives later this year. The 1TB drives are still working, so I'll split them into two pairs and add them to two other machines.
For home use it's pretty common to just use whatever you have available. If you have a home BTRFS RAID-1 setup you can just add a new disk at any time and after a balance operation the RAID-1 capacity will have increased by half the size of that disk. I have a spare 4TB disk sitting around for when I need an extra 2TB of usable space in my home server.
yep, that's one of the advantages of btrfs. It's also a disadvantage because it encourages you to mix old drives, possibly failing or at least close to or maybe beyond their expected lifespan, with new ones. That's not a risk I'd take with storage devices...at least, not for any important data that I didn't have backed up.
RE: CDDL vs GPL
Oh well my clients will be safe, their position is that they trust Canonical and will keep using it until/unless advised otherwise.
Your clients aren't at any risk - they haven't distributed CDDL+GPL binaries. GPL & CDDL only restrict distribution, not use. At most, they might have to compile their own spl and zfs modules (apt-get install spl-dkms zfs-dkms should be all that's needed). Or get you to do it. craig -- craig sanders <cas@taz.net.au>
On Wednesday, 7 March 2018 12:58:29 AM AEDT Craig Sanders via luv-main wrote:
On Tue, Mar 06, 2018 at 11:22:17PM +1100, Russell Coker wrote:
If you have any sort of enterprise use then you will have matched pairs.
I've been doing that at home for a long time. I resigned myself many years ago to always paying double the going price for storage because I always want RAID-1/mirrored-pairs. It means I have to put off some upgrades until I can afford, e.g. two x 4TB or two x 8TB drives instead of just one, but it is, IMO, worth it.
My main workstation has 500G, 240G, and 120G SSDs in a RAID-1 BTRFS configuration. I bought the 120G SSD for that system, the others weren't needed for other systems (the 500G one was from when I learned the difference between M.2 SATA and M.2 NVMe the expensive way).
OTOH, it does mean that when I upgrade my main machine, I have matched pairs of older drives to distribute amongst other machines. I'll probably be replacing a 4 x 1TB RAIDZ-1 pool with a pair of 8TB drives later this year. The 1TB drives are still working, so I'll split them into two pairs and add them to two other machines.
That only applies as long as none of them fail.
For home use it's pretty common to just use whatever you have available. If you have a home BTRFS RAID-1 setup you can just add a new disk at any time and after a balance operation the RAID-1 capacity will have increased by half the size of that disk. I have a spare 4TB disk sitting around for when I need an extra 2TB of usable space in my home server.
yep, that's one of the advantages of btrfs. It's also a disadvantage because it encourages you to mix old drives, possibly failing or at least close to or maybe beyond their expected lifespan, with new ones. That's not a risk I'd take with storage devices...at least, not for any important data that I didn't have backed up.
Well if you don't have a backup you will lose anyway eventually.
At most, they might have to compile their own spl and zfs modules (apt-get install spl-dkms zfs-dkms should be all that's needed). Or get you to do it.
That's about $200 cost and some annoyance. Not a big deal. -- My Main Blog http://etbe.coker.com.au/ My Documents Blog http://doc.coker.com.au/
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