Hesela / Research library
Research & analyses
Storage engineering, examined through sources, measurements and reproducible methods.
133 analyses · Page 5 of 5
Newest firstSATA and SAS link errors: what counters can and cannot diagnose
SATA error flags and SAS PHY counters identify observations in the I/O path, not the component that must be replaced. Preserve endpoint identity, timestamps and reset history before comparing counts. Historical field studies show why a disk-only view is incomplete, but their event shares are not modern SAS failure rates.
Sector-error prediction: what adaptive scrubbing gains
A 2017 simulation shortened error-detection time. That is not a measured reduction in data loss, and its accelerated-scrub budget is not the false-positive rate.
Silent corruption: reading a 1.53-million-drive field study
FAST 2008 recorded checksum mismatches on 0.86% of nearline and 0.065% of enterprise disks. Unequal observation times and detection coverage limit what these shares mean.
SSD firmware-hour failures: model, revision and runtime matter
A healthy wear indicator does not rule out a firmware-hour defect. Vendor advisories describe separate 32,768-, 40,000- and 28,224-hour issues with different affected models and recovery outcomes. Match the exact drive and firmware, then check fresh runtime evidence.
SSD sanitization: why TRIM and a successful command are not enough
File deletion, deallocation and sanitization establish different things. A FAST study, NIST SP 800-88r2 and NVMe status semantics explain what evidence to collect before an SSD leaves your control.
SSD thermal throttling: temperature and NVMe counters
A hot SSD reading, a thermal-management event and a drive failure are different observations. Historical fleet studies show platform-dependent temperature associations, not a universal failure threshold. NVMe exposes distinct temperature and action counters; their units, capabilities and specification revision determine what a reading can establish.
SSD wear indicators: estimates, failure evidence and NVMe scope
Percentage Used estimates consumed endurance; it is not a failure probability. Available Spare measures a different quantity, and a read-only warning is not a promise of continued data access. Historical SATA failures and Google's field study illustrate these limits, but neither calibrates modern NVMe warning coverage. Keep device identity, log identifier and counter scope with every observation.
What an unexpected power cut does to SSDs, and why power-loss protection is hard to check from outside
Historical power-fault tests exposed SSD data and ordering failures, including on devices labelled with PLP. Those outcomes do not identify a failed capacitor or establish a current-product failure rate.
What LTO TapeAlert can tell you about a failing tape, and what it cannot
TapeAlert reports conditions, not a cartridge failure rate. Flag meanings depend on whether the target is a drive or a library, and reading the log can clear the evidence. LTO error-rate specifications describe a separate model: they do not establish annual data durability or the health of unread data.
Why retrying a failed fsync does not prove durability
Why a successful fsync retry can leave stale data: historical research, Linux close errors, POSIX portability, synchronization boundaries and reproducible descriptor-lifetime observations.
Disk replacement rates are not disk lifetimes
Field replacement logs count operational decisions, not verified component lifetimes. Drive age, fleet event gaps and repeated-event rates answer different reliability questions.
Over 56% of failed drives had no count on the four strong SMART signals
Over 56% of failed drives in the Google production population of more than 100,000 consumer-grade serial and parallel ATA drives (December 2005–August 2006) had no count in any of the four strong SMART signals (scan errors, reallocation count, offline reallocation, and probational count), so models based only on those signals can never predict more than half of the failed drives.
What fails most often: unreadable data on disks, uncorrectable reads on SSDs, and bus errors on the link
The most frequent field fault is not a dead drive but data that cannot be read: 3.45% of 1.53 million hard disks developed at least one latent sector error in 32 months, and 20.3–90.5% of Google's flash drives (ten models, first 4 years; 3 for eMLC) had at least one uncorrectable error and 19.1–62.7% a final read error, while 4.2–34.1% of Facebook's SSD platforms reported at least one uncorrectable error. Link faults show up separately as CRC counts (about 2% of Google's disks), and the public counters miss a large share of failed drives: over 56% of failed drives in the Google study and 23.3% in Backblaze's 2016 log showed no signal on the SMART attributes each used.
Looking for a technology? Browse technology cards or open the knowledge corpus.