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Pro Pioneer - Poor performance X-RAID Raid-6 with 6x WD Red 3TB
For a really long time I thought the poor performance was due to the fact that I was running an old firmware and had never done a factory reset since 2009 (it was recommended in the past on the forum...
For future readers;
The performance impact boiled down to the following things:
- The RAID implementation currently works different in comparison to older versions of the NAS which has impact on performance, but delivers more reliability
- The implementation of NFS (and/or NFSv4) works different and by default works in a more reliable way. Using the "async" option will greatly improve the speed of transfers, but will greatly increase the risk of faulty transfers in case of power-failure and such
- Performance is (obviously) impacted when there are operations running (ie: (initial) (re)syncing of volumes, balancing, scrubbing, defragmentation, simultanious transfers, etc.)
I tested diskspeeds within my system to evaluate the performance impact. My conclusion for now is that in a RAID-5 or RAID-6 setup the set won't perform better than an individual disk (which was the case in older versions of ReadyNAS but seems to not be true anymore, probably due to the first point). When using the async option, the performance is equal to the individual disks. Note; I have *not* compared speeds using CIFS/Samba. I have tested one time and it seemed that the speeds were comparable to NFS with the async option turned on.
Thanks for the further explanation mdgm; I get that things changed, and therefore might affect resyncing. I also get that because it is a 5400 RPM disk it probably could (and would) perform less well than my initial Samsung Spinpoint 1TB (7200rpm).
However I find it hard to believe that when the disks individually performe well above 100 mb/sec, that a raid-5 setup would perform (way) worse than each individual disk. I find that a bit hard to believe :) as raid 5 (and 6) were generally considered to perform better. Not as good as a striping system, but better than mirrod setups and at least a bit faster than individual disks.
I still kind of suspect certain drives, but have no other (solid) evidence for them being faulty except that they sound a bit weird when in the NAS. I might try factory resetting again, and starting with 1 disk and gradually go up to multiple disks and see if I can pinpoint at which disk (if any) the problem arises.
In OS4 it was possible to totally re-initialize disks (so without initial sync). Is this possible in OS6 as well? Or do I always have to sync even when there was no data on the disks?
MaxxMark wrote:
In OS4 it was possible to totally re-initialize disks (so without initial sync). Is this possible in OS6 as well? Or do I always have to sync even when there was no data on the disks?
Even in OS4 you need to sync the full volume since RAID runs underneath the filesystem. Perhaps I am confused on what you mean???
If you are asking about setting up one volume per disk (jbod with no spanning), then the answer is that OS 6 lets you do this also. You can delete the volume you have now, and create new ones for each drive - so it is actually easier than OS 4.
StephenB wrote:Even in OS4 you need to sync the full volume since RAID runs underneath the filesystem. Perhaps I am confused on what you mean???
If you are asking about setting up one volume per disk (jbod with no spanning), then the answer is that OS 6 lets you do this also. You can delete the volume you have now, and create new ones for each drive - so it is actually easier than OS 4.
I thought (but reading your reply I guess I remembered wrong) that when you initialize a raid set from zero (ie: all disks are totally blank) it only needs to initialize the filesystem as it assumes it is empty. But it could be that I mixed things up in my mind (when setting up a mirror raid (raid 1) with Intel Storage Engine, it is just clicking create and do a quick format).
What I wanted to do is go through all the steps;
first create 1 disk; check performance
create 2 disk array; using raid 1 (mirror); check performance
create 3 disk array; using raid 5 (2 data 1 parity); check performance
create 4 disk array; using raid 6 (2 data, 2 parity); check performance
create 4 disk array; using raid 5 (3 data, 1 parity); check performance
And when the performance dips, try the same setup with another disk to rule out disk issues.
It'll probably (very) time consuming when the volume needs to resync everytime. But it's a gutfeeling that there is something wrong somewhere.
MaxxMark wrote:
StephenB wrote:Even in OS4 you need to sync the full volume since RAID runs underneath the filesystem. Perhaps I am confused on what you mean???
If you are asking about setting up one volume per disk (jbod with no spanning), then the answer is that OS 6 lets you do this also. You can delete the volume you have now, and create new ones for each drive - so it is actually easier than OS 4.
I thought (but reading your reply I guess I remembered wrong) that when you initialize a raid set from zero (ie: all disks are totally blank) it only needs to initialize the filesystem as it assumes it is empty. But it could be that I mixed things up in my mind (when setting up a mirror raid (raid 1) with Intel Storage Engine, it is just clicking create and do a quick format).
What I wanted to do is go through all the steps;
first create 1 disk; check performance
create 2 disk array; using raid 1 (mirror); check performance
create 3 disk array; using raid 5 (2 data 1 parity); check performance
create 4 disk array; using raid 6 (2 data, 2 parity); check performance
create 4 disk array; using raid 5 (3 data, 1 parity); check performance
And when the performance dips, try the same setup with another disk to rule out disk issues.
It'll probably (very) time consuming when the volume needs to resync everytime. But it's a gutfeeling that there is something wrong somewhere.
You certainly can do that with OS6 (just switch to flexraid and create whatever volumes you want).
Are you suspicious of all the disks, particular disks, or the RAID performance?
jbod creation is pretty fast, since there is no sync for that - so you could set up a 1-disk volume for each disk and measure performance on each as part of your first step.
Also, do RAID-6 last, since you can simply expand the 3-disk RAID-5 array to 4 disks, which might save some time.
You haven't mentioned SMART stats - have you looked at them?
I'm not suspicious of a disk in particular. Especially because the quick tests of the disks didnt show anything worth panicing about.
However the performance of the raid set as a whole is the thing that worries me. I just can't believe that disks which perform better individually (The WD Red (120-150mb/sec) compared to a Spinpoint HD103 (100-120 mb/sec) one on one outside of a RAID array) than they do in a raid set (RAID6 of 6x WD Red 3TB (30-60mb/sec) compared to RAID6 array of 6x Samsung Spinpoint 1TB (130+ mb/sec)).
SMART info has not really something noteworthy if you ask me. To be complete here is the volume.log after the most recent factory reset.
For now I have tested the following:
Disk 1 without other disks: speed was 100+ mb/s
Disk 2 without other disks: 100+ mb/s
At that moment I got curious and reverted to OS4 to check how that performed (noteworthy was that during factory reset you could at that time say you want raid6, which isnt possible in os6 anymore).
Performance of the resyncing was the same as was in OS6 (30 to 60mb/s). So the OS difference is not the cause (just as a sidenote; in the past when replacing a disk and doing online expansion, the resyncing was almost always above 80mb/sec).
After this I re-upgraded to OS6 again, which initializes as RAID5 again, and thats where I got the the above volume log containting smart info.
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