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SATA Experiences

SATA Experiences. HEPiX Spring 2005 Fermilab Ray Pasetes, Lisa Giacchetti. Type Of Storage. Enterprise Typically SCSI or Fibre Channel Very expensive, high performance Mid-Tier Enterpise SATA, FATA Higher MTBF than commodity 90-95% streaming performance of Enterprise drives Commodity

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SATA Experiences

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  1. SATA Experiences HEPiX Spring 2005 Fermilab Ray Pasetes, Lisa Giacchetti

  2. Type Of Storage • Enterprise • Typically SCSI or Fibre Channel • Very expensive, high performance • Mid-Tier • Enterpise SATA, FATA • Higher MTBF than commodity • 90-95% streaming performance of Enterprise drives • Commodity • SATA, ATA, IDE • 90-95% streaming performance of Enterprise drives

  3. Types of SATA storage • FC Controllers, SATA storage • Sierra Logics ATA-FC bridges • Custom ASICs • PCI/PCI-X controllers • Most RAID • Some JBOD

  4. You Get What You Pay For • Firmware • Fixed 512B blocks • No checksum per drive • Bad block allocation timeouts • Some ATA/IDE/SATA fw allows for 2 minutes • Head misalignments • Common for disks with high idle times while powered • Single processor for head movement and data movement • Higher activity in one causes the other to degrade • Hot Spots • Data corruption • Data checksummed and verified accurate at time t1, read back corrupt at time t2.

  5. You Get What You Pay For (2) • Dual Controller – just two words • May not mean controllers failover (at all ) • Each controller only handles ½ of RAID. • May not mean controllers failover automatically • System needs to be reset to have surviving controller take over. • May not be available • Option does not exist.

  6. You Get What You Pay For (3) • Stability of Unit • May find self as un-willing beta tester • FW updates introduce more problems than fixes • FW updates fix problem, breaks other features that were working • Often find bugs already known but not disclosed • Loss of data not as rare as one would expect • Upgrades are disruptive

  7. Under Investigation • Enterprise class “S/ATA” solutions • EMC • Still uses 250GB, 5400RPM PATA drives • LSI • 250GB, 7200RPM SATA • 1.25TB, 5400RPM SATA blades • HDS • 250GB, 7200RPM SATA • Vendors slow to adapt to new technology • None offer 400GB drives. • Some claim 400GB drives show 1/8 reliability in internal testing. May never adopt this drive.

  8. Under Investigation (2) • Tweaked SATA storage • FW changes • Allows for 520B blocks – can checksum per drive • Periodic head sweeps – prevents hot spots, misalignments • Perceived “better” testing of sw, hw, fw. • Some claim drives not available in open market • Upgrades are non-disruptive (dual-attach) • More expensive…but not too outrageous

  9. Understand Your Needs • Caching storage • Massive storage • Loss of disk access and data tolerable • Data also on tape or other storage medium • Low I/O. • Secondary storage • Loss of disk access somewhat tolerable • Downtimes allowable, usually off hours. • Loss of data NOT tolerable • Low I/O

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