Question/Problem: Mounting of XFS filesystem takes a lot of time
Hello,
thank you all for your emails with suggestions and comments on my problem.
When messing around with the BIOS settings (switching SATA mode from RAID to IDE) I get quite an obvious message stating that the S.M.A.R.T. status of one of the disks is BAD.
Removing that disk solved the problem. My system is mounting the remaining XFS partitions fast as usual.
Thanks again
Andi
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Check your disks. I've seen harddisks dying in that way. Suddenly access times are horrible. Test random access I/O and compare times, not sequential - those might still look good.
[ ... ] When messing around with the BIOS settings (switching SATA mode from RAID to IDE) I get quite an obvious message stating that the S.M.A.R.T. status of one of the disks is BAD. Removing that disk solved the problem. [ ... ]
The suggestion about checking disk error status was good, and relates to an important but little known detail about SATA vs. SAS disk drives.
Usually SATA drives are pogrammed to do a large number of firmware driven retries in case of data errors, hanging the IO subsystem, while SAS drives, which are expected to be used in RAID sets, don't, and report errors immediately. So called "Raid Edition" SATA drives often behave like SAS drives in this respect.
It is often possible but usually quite awkward to change that setting for ordinary SATA drives.
Disabling extended fw retries is usually a good idea with Linux anyhow, as it does sw retries anyhow, and very good for drives used in RAID sets with redundancy, to reduce latency in the case of errors.
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Le Thu, 21 Oct 2010 01:19:26 +0100 vous écriviez:
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Usually SATA drives are pogrammed to do a large number of firmware driven retries in case of data errors, hanging the IO subsystem,
This is only the case for Desktop SATA drives. More expensive "enterprise" SATA drives (Seagate ES or ES2 series, Hitachi Ultrastar, etc) behave like SAS drives.
Desktop SATA drives also lack the logic to manage properly vibrations happening in large arrays, which can totally kill performance.
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