> -----Original Message----- > From: Pavel Machek [mailto:pa...@ucw.cz] > Sent: Wednesday, January 30, 2013 4:37 AM > To: Amit Kale > Cc: LKML > Subject: Re: Announcement: STEC EnhanceIO SSD caching software for > Linux kernel > > Hi! > > > EnhanceIO driver is based on EnhanceIO SSD caching software product > developed by STEC Inc. EnhanceIO was derived from Facebook's open > source Flashcache project. EnhanceIO uses SSDs as cache devices for > traditional rotating hard disk drives (referred to as source volumes > throughout this document). > > > > EnhanceIO can work with any block device, be it an entire physical > disk, an individual disk partition, a RAIDed DAS device, a SAN volume, > a device mapper volume or a software RAID (md) device. > > > > The source volume to SSD mapping is a set-associative mapping based > on the source volume sector number with a default set size (aka > associativity) of 512 blocks and a default block size of 4 KB. Partial > cache blocks are not used. > > The default value of 4 KB is chosen because it is the common I/O > block > > size of most storage systems. With these default values, each cache > > set is 2 MB (512 * > > 4 KB). Therefore, a 400 GB SSD will have a little less than 200,000 > cache sets because a little space is used for storing the meta data on > the SSD. > > > > EnhanceIO supports three caching modes: read-only, write-through, and > write-back and three cache replacement policies: random, FIFO, and LRU. > > > > Read-only caching mode causes EnhanceIO to direct write IO requests > > only to HDD. Read IO requests are issued to HDD and the data read > from > > HDD is stored on SSD. Subsequent Read requests for the same blocks > are > > carried out from SSD, thus reducing their latency by a substantial > > amount. > > What are the requirements for the SSD? I have 500GB 2.5" HDD in the > notebook... and it starts to be slightly slow for git. Would cheap 8GB > USB stick be useful thing to cache at? (USB sticks have reasonably fast > "seek", but reads are in 20MB/sec range and writes are very > slow.)
Hi Pavel, Our testing primarily covered 100GB+ SSDs due to our focus on enterprise market. 8GB will work, but 500:8 is about 60times. Our recommendation is to keep SSD:HDD ratio between 1:5 and 1:10. I'll be most interested in knowing your findings. Thanks. -Amit PROPRIETARY-CONFIDENTIAL INFORMATION INCLUDED This electronic transmission, and any documents attached hereto, may contain confidential, proprietary and/or legally privileged information. The information is intended only for use by the recipient named above. If you received this electronic message in error, please notify the sender and delete the electronic message. Any disclosure, copying, distribution, or use of the contents of information received in error is strictly prohibited, and violators will be pursued legally. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
