June 22, 201115 yr I have 20 2TB hard drives in my unRaid array. One is for parity and one is a cache drive. When I started to calc parity the estimate was over 3,100 minutes - over 51 hours!! Is this normal?? Has anyone else calc'ed parity on an array this size? What type of calc times are you guys experiencing?...............
June 22, 201115 yr I have 20 2TB hard drives in my unRaid array. One is for parity and one is a cache drive. When I started to calc parity the estimate was over 3,100 minutes - over 51 hours!! Is this normal?? Has anyone else calc'ed parity on an array this size? What type of calc times are you guys experiencing?............... If you refresh the browser, does it still say the same estimate? The early estimates are grossly wrong because the disks may need to be spun up. See this in the FAQ in the wiki: http://lime-technology.com/wiki/index.php?title=FAQ#How_fast_should_my_parity_check_be.3F which will lead you to here in the wiki: http://lime-technology.com/wiki/index.php?title=User_Benchmarks and this to see how fast you really are compared to some: http://lime-technology.com/forum/index.php?topic=4493 If your speed has not improved, odds are one of your disks is in PIO mode. (emulated IDE mode with polled IO) That is typically a BIOS setting, although on old hardware, it could be a bad or incorrect cable. Only way to know is for you to follow the instructions at the top of this forum to attach a system log to your next post requesting help or guidance. http://lime-technology.com/forum/index.php?topic=9880.0 Another possibility is you are limited by a PCI bus bandwidth. That could do it too. Best if you describe your hardware (motherboard and disk controllers) Joe L.
June 22, 201115 yr I have 20 2T data disks, all "green" with a Hitachi 7200 RPM parity. I calculate parity in 8-8.5 hours.
June 22, 201115 yr Author BIOSTAR TA790GXB3 AM3 AMD 790GX ATX AMD Motherboard SYBA SY-PCI40010 PCI SATA II (3.0Gb/s) Controller Card (X 3) AMD Athlon II X2 245 Regor 2.9GHz Socket AM3 65W Dual-Core Desktop Processor Seagate green drives unRaid 4.7 according to the parity speed benchmarks it should only take 9-10 hours after 24 hours it was showing 50% complete - then the power went out & it started over. (Big storms here in Texas...) All disks were spun down at start..... So spinning up all disks prior to parity calc will speed things up? I'll attach syslog when I get home tonight.
June 22, 201115 yr BIOSTAR TA790GXB3 AM3 AMD 790GX ATX AMD Motherboard SYBA SY-PCI40010 PCI SATA II (3.0Gb/s) Controller Card (X 3) AMD Athlon II X2 245 Regor 2.9GHz Socket AM3 65W Dual-Core Desktop Processor Seagate green drives unRaid 4.7 according to the parity speed benchmarks it should only take 9-10 hours after 24 hours it was showing 50% complete - then the power went out & it started over. (Big storms here in Texas...) All disks were spun down at start..... So spinning up all disks prior to parity calc will speed things up? Not really. But the first estimate of the time it will take was based on the first block of parity calculated. That specific block includes the time to spin up the drives, so it took much longer. The second and subsequent blocks will take far less time. So.. If you take 30 seconds to spin up all the disks prior to starting a parity check, the check itself will take 30 seconds less, but only if all the disks were not spinning at the start. I'll attach syslog when I get home tonight. If after 24 hours it only showed 50% complete, then there is a hardware issue, or a setting issue, or a bandwidth issue with your hardware.
June 22, 201115 yr Your slow parity is probably caused by the three PCI SATA (4-port) cards you have. As I understand it, two SATA drives are about enough to saturate the whole PCI bus, and you've got 12 hooked up. So you end up going 1/6th the speed of other parity checkers. Now as others are getting parity checks done in about 8 to 10 hours, then yours should take 6 times as long or about 48 to 60 hours. Only way out of this is to replace two of those cards with one 8-port SATA card that is attached to an PCIe 4x slot. A popular one is the AOC-SASLP-MV8 (which is about $120 including the cables you need), see: http://lime-technology.com/forum/index.php?topic=11591.0;topicseen Regards, Stephen
June 22, 201115 yr A PCI slot can only support a single drive at full speed. Since you have 4 drives on the each PCI card multiply the normal completion time by 4. More if the PCI slots share bandwidth. This will affect parity calculation, parity checks, failed drive emulation, and drive rebuild speeds. It will also affect multiple concurrent reads from drives that share a card or PCI bandwidth. If the slow speed is a problem then consider getting a MB with at least 2 PCIex4 (or better) slots and use 8 SATA port PCIe controller cards.
June 22, 201115 yr The PCI based disk controllers would easily be the reason for the slow parity check speed. On my older unRAID server with 12 drives and the largest being 1TB it takes about 12 to 14 hours to calculate parity as it too is a PCI bus based motherboard. The entire PCI bus can only handle 133MB/s. You are reading 2TB = 2000GB = 2000000 MB 2,000,000 MB * 20 drives = 40,000,000 MB of data to be read 40,000,000 MB / 133MB/s = 300752 seconds = 5012 minutes = 83 hours. And that is if you are able to completely saturate the PCI bus. Joe L.
June 22, 201115 yr FYI: http://lime-technology.com/forum/index.php?topic=7526.0 and http://lime-technology.com/forum/index.php?topic=7520 ANSWER: Ditch the PCI bus. The performance impact comes into play during parity builds, parity checks, failed drive situation, drive rebuilds, simultaneous writes and simultaneous reads. The typical PCI bus has 133 MB/sec bandwidth total available across all devices. If you use 1 PCI SATA card and place 4 drives on the PCI bus, your maximum limit will be 33 MB/sec [133 / 4]. If you use 2 PCI SATA cards and place 8 drives on the PCI bus, your maximum limit will be 16.6 MB/sec [ 133 / 8]. If you use 3 PCI SATA cards and place 12 drives on the PCI bus, your maximum limit will be 11.08 MB/sec [133 / 12]. That's the theoretical limits. In reality your rates will be SLOWER because of resource contentions and overhead.
June 22, 201115 yr Author Got it............ Didn't realize the pci bus was so slow................ I'm only using 16 drives (4 more in the mail) so the math works: 14 data drives = 24,000,000 MB / 133MB/s = 180,451 seconds = 3008 minutes = 50 hours! Looks like I'm gonna be in the market for a new MB & PCIe 4x controller cards...............
June 22, 201115 yr If you find a board with 6 on board SATA, 1 PCIeX4, and 1 PCIeX1. You can support up to 16 drives. If it has a PCI slot you can support one more drive or a GigE card.
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