Ice_Black Posted June 11, 2012 Share Posted June 11, 2012 I understand that write speed is slow on UnRaid. I get average of 30MB/sec It would be great to improve write speed by double in the future version (maybe 5.1). Is it possible? Link to comment
mrow Posted June 11, 2012 Share Posted June 11, 2012 You would need SSDs for parity drives to speed up write speeds to the array. Just use a cache drive. Link to comment
PeterB Posted June 12, 2012 Share Posted June 12, 2012 I understand that write speed is slow on UnRaid. I get average of 30MB/sec That is about as good as it gets. The process of writing involves not only the write to the device you are writing to, but also a read from, and write to, the parity drive. Unless hard drive write speeds increase drastically, you're not going to see an improvement. It would be great to improve write speed by double in the future version (maybe 5.1). Is it possible? The only way to get an (apparent) improvement is to install a cache drive. I say 'apparent' because all you are doing is delaying the slow write to the destination device and, until that delayed write occurs, the data you have written is not protected by parity. Link to comment
bubbaQ Posted June 12, 2012 Share Posted June 12, 2012 Here my benchmarks so far. 2 WD 1TB Green 5400 in RAID0 for data. 2 WD 1TB Green 5400 in RAID0 for parity. Running dd from /dev/zero to the Areca volumes is about 120MB/sec sustained. Parity check is running now at about 150MB/sec. Writing to disk1 over SMB is around 70MB/sec sustained. It can be done... you need faster drives. Link to comment
chickensoup Posted June 12, 2012 Share Posted June 12, 2012 Here my benchmarks so far. 2 WD 1TB Green 5400 in RAID0 for data. 2 WD 1TB Green 5400 in RAID0 for parity. Running dd from /dev/zero to the Areca volumes is about 120MB/sec sustained. Parity check is running now at about 150MB/sec. Writing to disk1 over SMB is around 70MB/sec sustained. It can be done... you need faster drives. Is there any reason you chose to stripe green drives? This seems like an odd choice, unless you already had the drives ofc. This setup fascinates me and I may consider something similar for a second 'faster' unRAID server down the track.. Seems quite costly losing 50% storage per disk share though. Sent from my iPhone using Tapatalk Link to comment
bubbaQ Posted June 12, 2012 Share Posted June 12, 2012 I had the drives, and they are cheaper than black or blue WDs. I don't lose any space... they are in RAID-0, not RAID-5 RAID0 parity has some other benefits... it has some help to writes for other non-RAID0 drives, and if I want to go from 2TB to 3TB, all I have to do is expand the RAID0 array with another spare 1TB drive. I keep only 1 RAID0 data drive, just for the things I want "fast"... the other drives are all conventional unRAID drives, for storage. Link to comment
opentoe Posted June 12, 2012 Share Posted June 12, 2012 I understand that write speed is slow on UnRaid. I get average of 30MB/sec It would be great to improve write speed by double in the future version (maybe 5.1). Is it possible? Unraid isn't meant for speed. 30MB/sec is most likely what you'll see it top off at. If you want something like 95MB/sec then you'll have to go for a Synology type box. I have one and I get a constant 95MB/sec on write speeds. Link to comment
hdkhang Posted June 12, 2012 Share Posted June 12, 2012 I was thinking about RAID0 for the parity drive. I think it would suit me better than say a parity + cache setup. @bubbaQ When you mention writes to drive 1, is that drive the RAID0 array or a standard drive? Link to comment
bubbaQ Posted June 12, 2012 Share Posted June 12, 2012 Disk1 is RAID0. Parity is RAID0. The other drives are standard. Link to comment
dlewis23 Posted June 12, 2012 Share Posted June 12, 2012 Using the parity + cache with HITACHI 5K3000 drives I get 60 - 105 Mb/s write, if I take take the cache drive out I get about 40 - 45 Mb/s write speed. I say just get good drives and use the cache drive option to speed things up. Link to comment
chickensoup Posted June 12, 2012 Share Posted June 12, 2012 I don't lose any space... they are in RAID-0, not RAID-5 Sorry, for some reason I was thinking RAID-1 not RAID-0, brainfart. Having a striped parity drive + 1 data makes total sense. Out of curiousity, do you have disk1 as its own share? Do you set your disk1 to spin-down at all? Link to comment
bubbaQ Posted June 12, 2012 Share Posted June 12, 2012 I don't lose any space... they are in RAID-0, not RAID-5 Sorry, for some reason I was thinking RAID-1 not RAID-0, brainfart. Having a striped parity drive + 1 data makes total sense. Out of curiousity, do you have disk1 as its own share? Do you set your disk1 to spin-down at all? Yes, it is its own share, and it spins down (per Areca FW, not unRAID). Link to comment
hdkhang Posted June 12, 2012 Share Posted June 12, 2012 Disk1 is RAID0. Parity is RAID0. The other drives are standard. Would it be safe to say that the write speed to standard drives would be similar (i.e. 70MB/sec range) since the bottleneck is the parity drive? Link to comment
bubbaQ Posted June 13, 2012 Share Posted June 13, 2012 the bottleneck is the parity drive? The bottleneck is NOT the parity drive. It is the SLOWER of the parity drive and the data drive you are writing to. Link to comment
Joe L. Posted June 13, 2012 Share Posted June 13, 2012 the bottleneck is the parity drive? The bottleneck is NOT the parity drive. It is the SLOWER of the parity drive and the data drive you are writing to. It is the SLOWER ROTATIONAL SPEED of the parity drive and the data drive you are writing to. Each disk involved must make one rotation to read, and then rotate the platter one revolution to write the same sector. Faster spinning disks will be able to read and then write faster. (Both disks being 7200 RPM will result in faster throughput than when either is rotating at 5400 RPM) Link to comment
bubbaQ Posted June 13, 2012 Share Posted June 13, 2012 (Both disks being 7200 RPM will result in faster throughput than when either is rotating at 5400 RPM) Not always true. Areal density and throughput, along with the buffering algorithms can provide a 5400 RPM drive that will actually have faster writes in unRAID than a 7200 RPM drive. Link to comment
madburg Posted June 13, 2012 Share Posted June 13, 2012 (Both disks being 7200 RPM will result in faster throughput than when either is rotating at 5400 RPM) Not always true. Areal density and throughput, along with the buffering algorithms can provide a 5400 RPM drive that will actually have faster writes in unRAID than a 7200 RPM drive. I am not disagreeing with the logic, but could you share one make and model of a 5400 rpm drive that has the capabilities (proven) over a 7200 rpm drive. Link to comment
bubbaQ Posted June 14, 2012 Share Posted June 14, 2012 Sure. A WD20EARX (5400rpm) vs a WD400BB (7200rom) Link to comment
madburg Posted June 14, 2012 Share Posted June 14, 2012 A WD400BB (Legacy Product), really? Let's try something at the very least to be the same size and interface. Cache and amounts of platters (internals, etc) can be different. Your compare does hold up, not exactly something someone would second guess if going to a WD20EARX would be slower than a WD400BB Link to comment
JonathanM Posted June 14, 2012 Share Posted June 14, 2012 Sure. A WD20EARX (5400rpm) vs a WD400BB (7200rom) I've looked high and low on the interwebs, and I can't find a full spec sheet on the green drive. Are you SURE the seek times and latency are better? I know the transfer rates are better, but that's a result of more data passing by the head per second. I can't wrap my head around the concept of sequential reads and writes of the same sector being faster if the drive only brings that sector under the read heads once per revolution. Does it take more than 1 spin of the platter to get the job done on the older 7200 drive? Or does it take multiple rotations on all drives, and the newer electronics / heads / coils takes fewer rotations? How many licks does it take to get to the center of a tootsie roll pop? Link to comment
chickensoup Posted June 14, 2012 Share Posted June 14, 2012 A drive supporting NCQ would also likely take less rotations for r/w than one which does not. Link to comment
bubbaQ Posted June 14, 2012 Share Posted June 14, 2012 Heck, I've got a 32GB MTron SSD that is slower than the WD400BB! And sectors per track can make a big difference. If you have 3 times the SPT, you need 1/3 the revolutions to read/write the same amount of data! Consider this.... we have all seen drives that only have half the throughput on the inner cylinders than the outer cylinders. No consider a 7200 rpm drive that has performance due to the same topography on its outer cylinders of a 5400 rpm drive on its inner cylinders. Link to comment
marcusone Posted June 14, 2012 Share Posted June 14, 2012 I don't lose any space... they are in RAID-0, not RAID-5 Sorry, for some reason I was thinking RAID-1 not RAID-0, brainfart. Having a striped parity drive + 1 data makes total sense. Out of curiousity, do you have disk1 as its own share? Do you set your disk1 to spin-down at all? Yes, it is its own share, and it spins down (per Areca FW, not unRAID). Which Areca card do you have? Link to comment
madburg Posted June 14, 2012 Share Posted June 14, 2012 A drive supporting NCQ would also likely take less rotations for r/w than one which does not. NCQ is disabled by default in the unRAID settings (Force NCQ disabled = Yes). Link to comment
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