I managed to disable the write cache (did not know a tool on Solaris, hoever hdadm from the EON NAS binary_kit does the job):
Same power discuption test with Seagate HDD and write cache disabled ... --------------------------------------------------------------------------------------- r...@nexenta:/volumes# .sc/bin/hdadm write_cache display c3t5 c3t5 write_cache> disabled ... pull power cable of Seagate SATA Disk This is round number 4543 DONE This is round number 4544 DONE This is round number 4545 DONE This is round number 4546 DONE This is round number 4547 DONE This is round number 4548 DONE This is round number 4549 DONE This is round number 4550 <... hangs here> ... power cycle everything node1:/mnt/disk# cat testfile This is round number 4549 ... this looks good. So disabeling the write cache helps, but limits the performance really (not for synchronous but for async writes). Test with Intel X25-M -------------------------- ... Same with SSD r...@nexenta:/volumes# hdadm write_cache off c3t5 c3t5 write_cache> disabled r...@nexenta:/volumes# hdadm write_cache display c3t5 c3t5 write_cache> disabled .. pull SSD power cable This is round number 9249 DONE This is round number 9250 DONE This is round number 9251 DONE This is round number 9252 DONE This is round number 9253 DONE This is round number 9254 DONE This is round number 9255 DONE This is round number 9256 DONE This is round number 9257 <... hangs here> .. power cycle everything ... test node1:/mnt/ssd# cat testfile This is round number 9256 So without a write cache the device works correctly .... However be warned on boot the cache is enabled again: Device Serial Vendor Model Rev Temperature ------ ------ ------ ----- ---- ----------- c3t5d0p0 7200Y5160AGN ATA INTEL SSDSA2M160 02HD 255 C (491 F) r...@nexenta:/volumes# hdadm write_cache display c3t5 c3t5 write_cache> enabled Question: Does anyone know the impact of disabeling the write cache for the write amplification factor of the intel SSD's ? I would deploy Intel X25-M only for "mostly read" workloads anyway. Thus the performance impact of disabeling the write cache can be ignored. However if the life expectency of the device goes down without a write cache (I means it is MLC already!) - Bummer. And another Question: How can I permanently disable the write cache on the Intel X25-M SSD's ? Regards -- This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
