Hello zfs-discuss,
Server: x4500, 2x Opetron 285 (dual-core), 16GB RAM, 48x500GB
filebench/randomread script, filesize=256GB
2 disks for system, 2 disks as hot-spares, atime set to off for a
pool, cache_bshift set to 8K (2^13), recordsize untouched (default).
pool: 4x raid-z (5 disks) + 4x raid-z (6 disks) means that one pool
was created wit 4 raid-z1 groups each with 5 disks and another 4
raid-z1 groups each with 6 disks.
1. pool: 4x raid-z (5 disks) + 4x raid-z (6 disks)
(36 disks of usable space)
a. nthreads = 1 ~60 ops
b. nthreads = 4 ~250 ops
c. nthreads = 8 ~520 ops
d. nthreads = 128 ~1340 ops
1340/8 = 167 ops
2. pool: 2x raid-z2 (10 disks) + 2x raid-z2 (12 disks)
(36 disks of usable space)
a. nthreads = 1 ~50 ops
b. nthreads = 4 ~190 ops
c. nthreads = 8 ~360 ops
d. nthreads = 128 ~720 ops
720/4 = 180 ops
3. pool: 2x raid-z2 (22 disks)
(40 disks of usable space)
a. nthreads = 1 ~40 ops
b. nthreads = 4 ~120 ops
c. nthreads = 8 ~160 ops
d. nthreads = 128 ~345 ops
345/2 = 172 ops
4. pool: 4x raid-z (11 disks)
(40 disks of usable space)
a. nthreads = 1 ~50 ops
b. nthreads = 4 ~190 ops
c. nthreads = 8 ~340 ops
d. nthreads = 128 ~710 ops
710/4 = 177 ops
5. pool: 4x raid-z2 (11 disks)
(36 disks of usable space)
a. nthreads = 1 ~55 ops
b. nthreads = 4 ~200 ops
c. nthreads = 8 ~350 ops
d. nthreads = 128 ~760 ops
760/4 = 190 ops
6. pool:22x mirror (2 disks)
(22 disks of usable space)
a. nthreads = 1 ~75 ops
b. nthreads = 4 ~320 ops
c. nthreads = 8 ~670 ops
d. nthreads = 128 ~3900 ops
3900/22 = 177 ops
3900/44 = 88 ops (it's a read test after all)
Well, random reads really tends to give about 1-2x # of IOs of a
single disk in a raid-z[12] group. For some workloads it's really bad.
For some workloads I would definitely prefer much better random read
performance in terms of IO/s and trade in write performance.
Maybe something like raid-y[12] which are more like classical
raid-[56]? That way user would have a choice - good read performance
however excellent write performance, or just the opposite.
Right now RAID-Z1 and RAID-Z2 is just plainly horrible in terms of #
IOs for random-read environments when caching ratio is marginal.
This is especially painful with x4500.
--
Best regards,
Robert mailto:[EMAIL PROTECTED]
http://milek.blogspot.com
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