Mark Hahn wrote:
Here's a data point in favor of raw horsepower when considering software raid performance.
mostly sw r5 write performance, right?
Correct. Writes increased by 3X, Rewrites by 50%, Reads about the same.
Athlon K7 (18u) @ 840MHz, 1GB PC133, Abit KA7 Athlon XP 2800 @ 2075MHz, 1GB PC2700, Asus A7V400-MX
so your dram bandwidth (measured by stream, say) went from maybe .8 GB/s to around 2 GB/s. do you still have boot logs from the older configuration around? it would be interesting to know the in-cache checksumming speed gain, ie:
raid5: using function: pIII_sse (3128.000 MB/sec)
The Abit KA7 was the first consumer mobo to use leading+trailing mem clock and bank interleaving, so memory speed has only slightly more than doubled:
Athlon slot-A @ 850MHz + PC133 SDRAM ------------------------------------ kernel: raid5: measuring checksumming speed kernel: 8regs : 1285.600 MB/sec kernel: 32regs : 780.800 MB/sec kernel: pII_mmx : 1972.400 MB/sec kernel: p5_mmx : 2523.600 MB/sec kernel: raid5: using function: p5_mmx (2523.600 MB/sec) kernel: md: md driver 0.90.0 MAX_MD_DEVS=256, MD_SB_DISKS=27
Athlon XP @ 2075MHz + PC2700 DDR -------------------------------- kernel: raid5: measuring checksumming speed kernel: 8regs : 3172.800 MB/sec kernel: 32regs : 1932.400 MB/sec kernel: pIII_sse : 3490.800 MB/sec kernel: pII_mmx : 4868.400 MB/sec kernel: p5_mmx : 6229.200 MB/sec kernel: raid5: using function: pIII_sse (3490.800 MB/sec) kernel: md: md driver 0.90.0 MAX_MD_DEVS=256, MD_SB_DISKS=27
I'm also experimenting with this patch to see if the xor hardwire for modern intel/AMD architectures is still valid. With the old processor p5_mmx was always picked and always within a few MB/s. The new XP is all over the map.
pre-patch: always pIII_sse (35xx) post-patch: always p5_mmx (62xx)
--- ./include/asm-i386/xor.h.orig Fri Aug 2 17:39:45 2002
+++ ./include/asm-i386/xor.h Sun Jan 9 22:32:37 2005
@@ -876,3 +876,8 @@
deals with a load to a line that is being prefetched. */
#define XOR_SELECT_TEMPLATE(FASTEST) \
(cpu_has_xmm ? &xor_block_pIII_sse : FASTEST)
+
+/* This may have been true in 1998, but lets try what appears to be
+ nearly 4x faster */
+#define XOR_SELECT_TEMPLATE(FASTEST) \
+ (cpu_has_xmm ? &xor_block_p5_mmx : FASTEST)- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
