Hello. I'm finally ready to start using SnapRaid and on my first sync I got this warning: "WARNING! Your CPU doesn't have a fast implementation for triple parity. It's recommended to switch to 'z-parity' instead than '3-parity'."
This is an older server with dual AMD Opteron 2431 6-core procs (12 cores total). I do need triple parity for my config as it is 21 data drives and 3 parity, and eventually there will be 5 instances of SnapRaid running - each 21 drives with 3 parity.
I thought I read that SnapRaid is single threaded, so I take it by the warning that I should probably look at upgrading. I'm posting as I am looking for feedback on how fast of a system I should look at upgrading to in order to perform nightly sync operations on 5 instances of SnapRaid.
Thanks for your help, and now I'm off to Slickdeals to see what kind of deals are out there...!
-vorpel
edit: corrected warning message
Last edit: Vorpel 2014-07-16
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http://snapraid.sourceforge.net/manual.html
7.3 z-parity FILE
...
"This format is similar, but faster, at the one used by the ZFS RAIDZ3, but it doesn't work beyond triple parity"
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Okay, I got the parity going with the 3rd parity set as "z-parity" instead of "3-parity".
I am currently processing at 374 MiB/s with CPU at 44%. Total estimated time is 50 hours (this is on 21 Seagate 4TB NAS drives for data and 3 Seagate 4TB NAS drives for parity).
If I'm reading the FAQ correctly, the test that was done with an Intel Core i7-3470QM, the sync command rate for SSSE3 was 8,616 MiB/s.
If that is true, then I'm woefully underpowered and a CPU upgrade is very warranted...
Can anyone confirm that this is the case for me?
Thanks!
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A faster CPU would almost certainly help your sync throughput. 374 MiB/s is quite bad for 21 data drives. I get over 1000 MiB/s with 14 data drives. I have a Xeon E3-1270 V2 CPU at 3.5 GHz. My previous CPU was a slower Xeon, and when I upgraded to this faster Xeon, my maximum throughput went up from 800 MiB/s to well over 1000 MiB/s. And I am only using dual parity, and my old Xeon was much faster than your old Opteron.
I don't think the CPU percentage that SnapRAID displays is useful. I have not examined the code to see what it exactly SnapRAID is doing to compute that number, but I know that the CPU figure that SnapRAID displays on my system is signficantly lower than the CPU percentage of a single core that SnapRAID actually consumes on my system -- SnapRAID shows around 25% CPU or less, while htop shows me that the SnapRAID process is using more than 50% of a core.
By the way, you are NOT reading the FAQ correctly. The FAQ is merely stating the computational speeds for certain computations. The sync speed is affected by running both parity and hash computations at the same time, in the same thread, and also is limited by the IO speed of your drives.
But you can at least get an idea of how fast your CPU is at running the computations by executing snapraid -T
Last edit: jwill42 2014-07-17
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Hi Vorpel, I do have experience only with a small SR config, though, 4 not 24 disks. Anyway, the bottleneck I think is not yet the CPU, but the 3 parity disks. The data simply doesn't get fast enough onto the parity disks. Also, the slowest parity disk determines final throughput. If those 3 disks would be really FAST in writing, you should reach much more (till CPU limit reached ;-). I think that's why some guys have a parity raids of smaller disks for maximum write performance.
Just my 2 cents here ;-)
Cheers,
Jens.
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Thanks for the reply. Hmmm - this is also my primary system for media and I'm running Plex so I'm researching if the processor upgrade will help out there as well.
Since I am new to SnapRaid, the sync command is running now and doing the initial setup. For doing updates, will the sync command take as long?
I'll see what I can find online tonight...!
Thanks!
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Plex, nice, I've moved from PS3MediaCenter and Serviio to it. Just love it and the html5 support on all mobile devices...
And Sick Beard of course...
Well, the initial sync takes time. But you can expect any change to your data should perform around the 375 MB/sec you currently see. So, if only 20 GB change (last modified date changed on the files) since last sync, it should take only a minute or so for the parity writes. But don't forget about the data disk file scanning... that can take some time depending on the file system and # of files.
I'm sure you won't regret the move to SR!
Cheers.
Last edit: Jens Bornemann 2014-07-17
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Hello. I'm finally ready to start using SnapRaid and on my first sync I got this warning: "WARNING! Your CPU doesn't have a fast implementation for triple parity. It's recommended to switch to 'z-parity' instead than '3-parity'."
This is an older server with dual AMD Opteron 2431 6-core procs (12 cores total). I do need triple parity for my config as it is 21 data drives and 3 parity, and eventually there will be 5 instances of SnapRaid running - each 21 drives with 3 parity.
I thought I read that SnapRaid is single threaded, so I take it by the warning that I should probably look at upgrading. I'm posting as I am looking for feedback on how fast of a system I should look at upgrading to in order to perform nightly sync operations on 5 instances of SnapRaid.
Thanks for your help, and now I'm off to Slickdeals to see what kind of deals are out there...!
-vorpel
edit: corrected warning message
Last edit: Vorpel 2014-07-16
http://snapraid.sourceforge.net/manual.html
7.3 z-parity FILE
...
"This format is similar, but faster, at the one used by the ZFS RAIDZ3, but it doesn't work beyond triple parity"
Thanks for the info - I missed that.
I'll give that a try!
Okay, I got the parity going with the 3rd parity set as "z-parity" instead of "3-parity".
I am currently processing at 374 MiB/s with CPU at 44%. Total estimated time is 50 hours (this is on 21 Seagate 4TB NAS drives for data and 3 Seagate 4TB NAS drives for parity).
If I'm reading the FAQ correctly, the test that was done with an Intel Core i7-3470QM, the sync command rate for SSSE3 was 8,616 MiB/s.
If that is true, then I'm woefully underpowered and a CPU upgrade is very warranted...
Can anyone confirm that this is the case for me?
Thanks!
A faster CPU would almost certainly help your sync throughput. 374 MiB/s is quite bad for 21 data drives. I get over 1000 MiB/s with 14 data drives. I have a Xeon E3-1270 V2 CPU at 3.5 GHz. My previous CPU was a slower Xeon, and when I upgraded to this faster Xeon, my maximum throughput went up from 800 MiB/s to well over 1000 MiB/s. And I am only using dual parity, and my old Xeon was much faster than your old Opteron.
I don't think the CPU percentage that SnapRAID displays is useful. I have not examined the code to see what it exactly SnapRAID is doing to compute that number, but I know that the CPU figure that SnapRAID displays on my system is signficantly lower than the CPU percentage of a single core that SnapRAID actually consumes on my system -- SnapRAID shows around 25% CPU or less, while
htopshows me that the SnapRAID process is using more than 50% of a core.By the way, you are NOT reading the FAQ correctly. The FAQ is merely stating the computational speeds for certain computations. The sync speed is affected by running both parity and hash computations at the same time, in the same thread, and also is limited by the IO speed of your drives.
But you can at least get an idea of how fast your CPU is at running the computations by executing
snapraid -TLast edit: jwill42 2014-07-17
Hi Vorpel, I do have experience only with a small SR config, though, 4 not 24 disks. Anyway, the bottleneck I think is not yet the CPU, but the 3 parity disks. The data simply doesn't get fast enough onto the parity disks. Also, the slowest parity disk determines final throughput. If those 3 disks would be really FAST in writing, you should reach much more (till CPU limit reached ;-). I think that's why some guys have a parity raids of smaller disks for maximum write performance.
Just my 2 cents here ;-)
Cheers,
Jens.
Thanks for the reply. Hmmm - this is also my primary system for media and I'm running Plex so I'm researching if the processor upgrade will help out there as well.
Since I am new to SnapRaid, the sync command is running now and doing the initial setup. For doing updates, will the sync command take as long?
I'll see what I can find online tonight...!
Thanks!
Plex, nice, I've moved from PS3MediaCenter and Serviio to it. Just love it and the html5 support on all mobile devices...
And Sick Beard of course...
Well, the initial sync takes time. But you can expect any change to your data should perform around the 375 MB/sec you currently see. So, if only 20 GB change (last modified date changed on the files) since last sync, it should take only a minute or so for the parity writes. But don't forget about the data disk file scanning... that can take some time depending on the file system and # of files.
I'm sure you won't regret the move to SR!
Cheers.
Last edit: Jens Bornemann 2014-07-17