May 21, 201511 yr I am running unraid 5.0.5, and recently I've noticed that my read performance is terrible (at times). I decided to run some diagnostics using hdparm -tT. Here is the result for one of my data drives: /dev/sdd: Timing cached reads: 1038 MB in 2.00 seconds = 519.20 MB/sec Timing buffered disk reads: 12 MB in 3.16 seconds = 3.79 MB/sec This is way out of line with the other drives, such as: /dev/sdc: Timing cached reads: 1490 MB in 2.00 seconds = 744.54 MB/sec Timing buffered disk reads: 418 MB in 3.01 seconds = 138.67 MB/sec Here is the hdparm info for the slow drive: /dev/sdd: ATA device, with non-removable media Model Number: ST31000528AS Serial Number: 6VP240NB Firmware Revision: CC38 Transport: Serial Standards: Used: unknown (minor revision code 0x0029) Supported: 8 7 6 5 Likely used: 8 Configuration: Logical max current cylinders 16383 16383 heads 16 16 sectors/track 63 63 -- CHS current addressable sectors: 16514064 LBA user addressable sectors: 268435455 LBA48 user addressable sectors: 1953525168 Logical/Physical Sector size: 512 bytes device size with M = 1024*1024: 953869 MBytes device size with M = 1000*1000: 1000204 MBytes (1000 GB) cache/buffer size = unknown Nominal Media Rotation Rate: 7200 Capabilities: LBA, IORDY(can be disabled) Queue depth: 32 Standby timer values: spec'd by Standard, no device specific minimum R/W multiple sector transfer: Max = 16 Current = ? Recommended acoustic management value: 254, current value: 0 DMA: mdma0 mdma1 mdma2 udma0 udma1 udma2 udma3 udma4 udma5 *udma6 Cycle time: min=120ns recommended=120ns PIO: pio0 pio1 pio2 pio3 pio4 Cycle time: no flow control=120ns IORDY flow control=120ns Commands/features: Enabled Supported: * SMART feature set Security Mode feature set * Power Management feature set * Write cache * Look-ahead * Host Protected Area feature set * WRITE_BUFFER command * READ_BUFFER command * DOWNLOAD_MICROCODE SET_MAX security extension * Automatic Acoustic Management feature set * 48-bit Address feature set * Device Configuration Overlay feature set * Mandatory FLUSH_CACHE * FLUSH_CACHE_EXT * SMART error logging * SMART self-test * General Purpose Logging feature set * WRITE_{DMA|MULTIPLE}_FUA_EXT * 64-bit World wide name Write-Read-Verify feature set * WRITE_UNCORRECTABLE_EXT command * {READ,WRITE}_DMA_EXT_GPL commands * Segmented DOWNLOAD_MICROCODE * Gen1 signaling speed (1.5Gb/s) * Gen2 signaling speed (3.0Gb/s) * Native Command Queueing (NCQ) * Phy event counters Device-initiated interface power management * Software settings preservation * SMART Command Transport (SCT) feature set * SCT Read/Write Long (AC1), obsolete * SCT Write Same (AC2) * SCT Error Recovery Control (AC3) * SCT Features Control (AC4) * SCT Data Tables (AC5) unknown 206[12] (vendor specific) Security: Master password revision code = 65534 supported not enabled not locked not frozen not expired: security count supported: enhanced erase 166min for SECURITY ERASE UNIT. 166min for ENHANCED SECURITY ERASE UNIT. Logical Unit WWN Device Identifier: 5000c5001b892a49 NAA : 5 IEEE OUI : 000c50 Unique ID : 01b892a49 Checksum: correct I see no obvious explanation for this. A recent parity check came back clean. Any ideas? Could it be a bad SATA cable? Something like that?
May 22, 201511 yr Author OK, I decided to shut the array down and swap out the SATA cable. This made no difference in hdparm read performance. Then, I swapped out with a spare drive and tested this new drive with hdparm and got much better results. These tests indicate a problem with the original hard drive, so I swapped it out of the array and I am not rebuilding from parity.
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