Looking forward to see your test report from intel x-25 and ocz vertex 2 pro...
Thanks. Fred -----Original Message----- From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-boun...@opensolaris.org] On Behalf Of Arne Jansen Sent: 星期四, 六月 24, 2010 16:15 To: Roy Sigurd Karlsbakk Cc: OpenSolaris ZFS discuss Subject: Re: [zfs-discuss] Crucial RealSSD C300 and cache flush? Hi, Roy Sigurd Karlsbakk wrote: > Crucial RealSSD C300 has been released and showing good numbers for use as > Zil and L2ARC. Does anyone know if this unit flushes its cache on request, as > opposed to Intel units etc? > I had a chance to get my hands on a Crucial RealSSD C300/128MB yesterday and did some quick testing. Here are the numbers first, some explanation follows below: cache enabled, 32 buffers: Linear read, 64k blocks: 134 MB/s random read, 64k blocks: 134 MB/s linear read, 4k blocks: 87 MB/s random read, 4k blocks: 87 MB/s linear write, 64k blocks: 107 MB/s random write, 64k blocks: 110 MB/s linear write, 4k blocks: 76 MB/s random write, 4k blocks: 32 MB/s cache enabled, 1 buffer: linear write, 4k blocks: 51 MB/s (12800 ops/s) random write, 4k blocks: 7 MB/s (1750 ops/s) linear write, 64k blocks: 106 MB/s (1610 ops/s) random write, 64k blocks: 59 MB/s (920 ops/s) cache disabled, 1 buffer: linear write, 4k blocks: 4.2 MB/s (1050 ops/s) random write, 4k blocks: 3.9 MB/s (980 ops/s) linear write, 64k blocks: 40 MB/s (650 ops/s) random write, 64k blocks: 40 MB/s (650 ops/s) cache disabled, 32 buffers: linear write, 4k blocks: 4.5 MB/s, 1120 ops/s random write, 4k blocks: 4.2 MB/s, 1050 ops/s linear write, 64k blocks: 43 MB/s, 680 ops/s random write, 64k blocks: 44 MB/s, 690 ops/s cache enabled, 1 buffer, with cache flushes linear write, 4k blocks, flush after every write: 1.5 MB/s, 385 writes/s linear write, 4k blocks, flush after every 4th write: 4.2 MB/s, 1120 writes/s The numbers are rough numbers read quickly from iostat, so please don't multiply block size by ops and compare with the bandwidth given ;) The test operates directly on top of LDI, just like ZFS. - "nk blocks" means the size of each read/write given to the device driver - "n buffers" means the number of buffers I keep in flight. This is to keep the command queue of the device busy - "cache flush" means a synchronous ioctl DKIOCFLUSHWRITECACHE These numbers contain a few surprises (at least for me). The biggest surprise is that with cache disabled one cannot get good data rates with small blocks, even if one keeps the command queue filled. This is completely different from what I've seen from hard drives. Also the IOPS with cache flushes is quite low, 385 is not much better than a 15k hdd, while the latter scales better. On the other hand, from the large drop in performance when using flushes one could infer that they indeed flush properly, but I haven't built a test setup for that yet. Conclusion: From the measurements I'd infer the device makes a good L2ARC, but for a slog device the latency is too high and it doesn't scale well. I'll do similar tests on a x-25 and ocz vertex 2 pro as soon as they arrive. If there are numbers you are missing please tell me, I'll measure them if possible. Also please ask if there are questions regarding the test setup. -- Arne _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
