On 01/15/2014 08:03 AM, Robert van Leeuwen wrote:
Power-Loss Protection: In the rare event that power fails while the
drive is operating, power-loss protection helps ensure that data isn’t
corrupted.
Seems that not all power protected SSDs are created equal:
http://lkcl.net/reports/ssd_analysis.html
The m500 is not tested but the m4 is.
Up to now it seems that only Intel seems to have done his homework.
In general they *seem* to be the most reliable SSD provider.
Even at that, there has been some concern on the list (and lkml) that
certain older Intel drives without super-capacitors are ignoring
ATA_CMD_FLUSH, making them very fast (which I like!) but potentially
dangerous (boo!). The 520 in particular is a drive I've used for a lot
of Ceph performance testing but I'm afraid that if it's not properly
handling CMD FLUSH requests, it may not be indicative of the performance
folks would see on other drives that do.
On the third hand, if drives with supercaps like the Intel DC S3700 can
safely ignore CMD_FLUSH and maintain high performance (even when there
are a lot of O_DSYNC calls, ala the journal), that potentially makes
them even more attractive (and that drive already has relatively high
sequential write performance and high write endurance).
Cheers,
Robert van Leeuwen
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