Comparing Hummingbird with EFS and XFS: single thread.

We compared Hummingbird with EFS and XFS on SGI IRIX. EFS is an extent file system. XFS is a high-performance journalling file system that interacts with the kernel through the traditional VFS and vnode interfaces.

We experimented with 3 different disk sizes, 4 GB, 9 GB, and 18 GB. Since EFS supports file systems up to 8 GB in size, we could not test it with 9 or 18 GB disks. Table 4 presents results where wg-Squid cache and the IRIX buffer cache together use 256 MB of main memory, which are divided in two ways: 50 MB $+$ 206 MB and 128 MB $+$ 128 MB (wg-Squid and buffer cache, respectively). The 50 MB for the wg-Squid was selected according to the Squid administration guidelines [23]. Hummingbird has 256 MB of main memory, and it has the best choice of policies as previously discussed.

Our experimental results are in Table 4. Hummingbird throughput is much higher than both XFS and EFS on the same disk size as seen in the UFS experiments, and the user-perceived latency (5th column in Table 4) is smallest in Hummingbird. The second observation from Table 4 is that EFS is much slower than XFS, which is a journalling file system. In particular, file system write time for EFS is more than 3 times larger than XFS write time. It is the result of frequent synchronous write operations for meta-data, which are performed by EFS. The third observation is that increasing wg-Squid cache size to 128MB and reducing the file system buffer cache size actually improved the file system performance, which indicates that the wg-Squid cache is more effective than the file system buffer cache.

Table 4: Comparing Hummingbird with XFS and EFS with 256 MB of main memory when all files are cached.

file	disk	cache	proxy	FS read	FS write	# of disk	mean disk	experiment
system	size	size (MB)	hit rate	time (ms)	time (ms)	I/Os	I/O time (ms)	run time (s)
Hum	4 GB	256	0.62	2.82	0.20	922,871	9.85	9,926
EFS	4 GB	50$+$206	0.62	14.79	46.38	10,784,969	10.99	128,878
XFS	4 GB	50$+$206	0.62	14.97	16.56	10,870,353	6.67	75,565
EFS	4 GB	128$+$128	0.62	14.08	48.33	10,540,778	11.37	130,359
XFS	4 GB	128$+$128	0.62	14.90	13.95	10,115,369	6.72	70,746
Hum	9 GB	256	0.66	3.30	0.21	1,028,922	10.77	11,861
XFS	9 GB	50$+$206	0.66	15.47	12.39	9,558,954	7.02	69,929
XFS	9 GB	128$+$128	0.66	15.65	8.80	8,737,878	7.12	64,726
Hum	15 GB	256	0.67	3.71	0.21	1,049,121	11.92	13,313
XFS	15 GB	50$+$206	0.67	16.71	5.73	8,103,576	7.60	63,371
XFS	15 GB	128$+$128	0.67	15.91	5.79	7,841,184	7.55	60,943