My storage 6540 is running slow. Volumes I map to server have write speed average at 5MB/s.
I want to tray this issue from cache policy. This is cache options I find from collection data about a volume.
Read cache active: true
Write cache enabled: true
Write cache active: false
Write cache without batteries: false
Write cache with mirroring enabled: true
Write cache with mirroring active: false
Is it affect to my I/O ? Can I change this option? Where to find documents about cache policy of storage 6000 family.
Hi i found this today, so i will have to replace a new Battery before furthur tracking.
A battery fault can cause write cache to become disabled. Write cache will not be re-enabled until the battery has been replaced and fully charged. A newly replaced battery can take upwards of 12 hours to recharge.
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Battery is there to ensure write cache can be maintained during a power failure. Enabling write cache without battery (btw, not a user option) is a dangerous proposition bec. once an I/O request is written to cache by the controller, it is considered complete and the host application will be informed with an i/o success. The lost of write cache before the content is written to disk, means data lost that is completely undetectable by the host application unless the host file system structure provide alternative error detection mechanism (such as a block level checksum). This data corruption can potentially go undetected forever since as far as the host is concerned it was successfully written, while on the storage side, the RAID structure (if any) is intact and there would be no parity check error since write cache was "lost" and not bec. it was partially written.
It's a good idea to keep write cache disabled while waiting for a new battery.