> Hi, > Out of pure curiosity, I was wondering, what would > happen if one tries to use a regular 7200RPM (or 10K) > drive as slog or L2ARC (or both)?
I have done both with success. At one point my backup pool was a collection of USB attached drives (please keep the laughter down) with dedup=verify. Solaris' slow USB performance coupled with slow drives and dedup reads gave abysmal write speeds, so much so that at times it had trouble keeping the snapshots synchronized. To help it along, I took an unused fast, small SCSI disk and made it L2ARC, which significantly improved write performance on the pool. During testing of some iSCSI applications, I ran into a scenario where a client was performing many small, synchronous writes to a zvol in a wide RAIDZ3 stripe. Since synchronous writes can double the write activity (once for the zil and once for the actual pool), actual throughput from the client was below 2MB/s, even though the pool would sustain 200MB/s on sequential writes. As above, I added a mirrored slog which was two small, fast SCSI drives. While I expected the throughput to double, it actually went up by a factor of 4, to 8MB/s. Even though 8MB/s wasn't mind-numbing, it was enough that it was close to saturating the client's 100Mb ethernet link, so it was ok. I think the reason that the slog improved things so much is that the slog disks were not bothered with other i/o and were doing very little seeking. -- This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
