December 2, 201213 yr I have a samsung (HD203WI) that I've isolated as the source for some very slow parity checks. Previously I was getting 90MB/sec+ parity checks on a 12 disk + parity system, but the past few days have been around 23MB/sec. Nothing showed up in syslog and the SMART tests all passed. However, when I run hdparm I get some interesting results: root@Hal:~# hdparm -tT /dev/sdk /dev/sdk: Timing cached reads: 19782 MB in 2.00 seconds = 9915.27 MB/sec Timing buffered disk reads: 28 MB in 3.10 seconds = 9.02 MB/sec root@Hal:~# hdparm -tT /dev/sdl /dev/sdl: Timing cached reads: 21672 MB in 1.99 seconds = 10864.71 MB/sec Timing buffered disk reads: 280 MB in 3.00 seconds = 93.26 MB/sec /dev/sdk is the Samsung drive which just tested @ 1.68 MB/sec and is going to be replaced. It is definitely the drive as I've moved another drive to its slot and it tests fine, move the Samsung to a known good port/cable and it remains slow. I have actually seen this once before in an iMac... drive performance was abysmal yet every hardware test passed with flying colors. Once I replace the drive, I'm going to setup automated hdparm tests once a week in case this happens again. But I am really curious what causes this when all tests pass and nothing gets logged. Any ideas?
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